Pediatric Clinical Pharmacology 2011

Handbook of Experimental Pharmacology
Volume 205
Editor-in-Chief
F.B. Hofmann, München
Editorial Board
J.A. Beavo, Seattle, WA
J.E. Barrett, Philadelphia
D. Ganten, Berlin
P. Geppetti, Florence
J.-A. Karlsson, Singapore
M.C. Michel, Ingelheim, Germany
C.P. Page, London
W. Rosenthal, Berlin
For further volumes:

http://www.springer.com/series/164
.
Hannsjörg W. Seyberth l Anders Rane
Matthias Schwab
Editors
Pediatric Clinical
Pharmacology
Editors Prof. Dr. Anders Rane
Prof. em. Dr. Hannsjörg W. Seyberth Karolinska University Hospital
Klinik für Kinder- und Jugendmedizin Karolinska Institutet
Philipps-Universität Marburg Dept. Laboratory Medicine
Baldingerstraße Div. Clinical Pharmacology
35043 Marburg, Germany Stockholm
Sweden
Present address: anders.rane@ki.se
Lazarettgarten 23
76829 Landau
Germany
seyberth@staff.uni-marburg.de
Prof. Dr. Matthias Schwab

Dr. Margarete Fischer-Bosch-
Institut für Klinische Pharmakologie (IKP)
Auerbachstrasse 112
70376 Stuttgart
Germany
Department of Clinical Pharmacology

Institute of Experimental and Clinical
Pharmacology and Toxicology
University Hospital
Tübingen
Germany
matthias.schwab@ikpstuttgart.de
ISSN 0171-2004 e-ISSN 1865-0325

ISBN 978-3-642-20194-3 e-ISBN 978-3-642-20195-0
DOI 10.1007/978-3-642-20195-0
Springer Heidelberg Dordrecht London New York
Library of Congress Control Number: 2011937023
# Springer-Verlag Berlin Heidelberg 2011

This work is subject to copyright. All rights are reserved, whether the whole or part of the material is
concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting,
reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication
or parts thereof is permitted only under the provisions of the German Copyright Law of September 9,
1965, in its current version, and permission for use must always be obtained from Springer. Violations
are liable to prosecution under the German Copyright Law.
The use of general descriptive names, registered names, trademarks, etc. in this publication does not
imply, even in the absence of a specific statement, that such names are exempt from the relevant protec-
tive laws and regulations and therefore free for general use.
Printed on acid-free paper
Springer is part of Springer Science+Business Media (www.springer.com)

Preface
Historical development of pediatric pharmacology started at the very beginning of

pharmacology and pediatrics in the mid-nineteenth century. Actually, in many
places both medical disciplines stem from the same origin, the urban polyclinics
or ambulances.
Already in the first therapeutic textbooks in pediatrics, often written by pharma-
cologists, it was stated that children are not small adults as demonstrated by the fact
that the volume of distribution (Vd) for many drugs is larger in infants and drug
reactions can be quite different in young children as seen with opiates, aspirin, and
caffeine.
Unfortunately with the entry into a more scientific area at the beginning of the
twentieth century pharmacology and pediatrics took up different paths. On the one
hand, the pharmacologists became more and more fascinated by the options of
learning more about the autonomic nervous system from studies with experimental
animals, and on the other hand, the pediatricians discovered the enormous impact of
microbiology for the prevention and treatment of infectious diseases and impact of
biochemistry for the development of age appropriate nutrition, especially for
infants. At the same time with losing interest in pediatric pharmacology pediatric
teachers have started to propagate pharmacotherapeutic nihilism, especially for
newborns and infants with the arguments of (a) lack of appropriate pediatric
formulations and age appropriate posology, (b) unpredictable effects of maturation
and development on pharmacokinetics and pharmacodynamics and vice versa, (c)
effects of drugs on maturation and development, and (d) last but not least of missing
verbal communication with very young children, which considerably reduced the
options of assessing drug efficacy and tolerance in this young pediatric population.
With this history in mind, it is not at all surprising that in the 1970s when several
modern pediatrics subspecialties like oncology, neonatal intensive care, cardiology,
and transplantation with the need of extensive drug treatment appeared on the
scene, the orphan drug status became more and more obvious. Many pediatricians
and pediatric scientists in academic institutions and in pharmaceutical industry
have lost or even never gained interest and professional competence in pediatric
v
vi Preface
pharmacotherapeutics. This has led to a widespread off label use of highly potent
but also precarious modern medicines especially in the very young and very sick
pediatric population.
The objective of this volume is to overcome in part some of these gaps by giving
an overview of the present state of the art of pediatric clinical pharmacology
including developmental physiology, pediatric-specific pathology, special tools
and methods for development of drugs for children (assessment of efficacy, toxicity,
long-term safety, etc.) as well as regulatory and ethical knowledge and skills. In the
future, structural and educational changes have to lead back to a closer cooperation
and interaction of pediatrics with (clinical) pharmacology and pharmacy. Medical
faculties and learned societies might consider establishing a tenure track system for
well-trained pediatric pharmacologists. Moreover, the young general pediatrician
needs to be better trained in the basics of pediatric drug treatment. Hopefully,
pediatric pharmacology will not end with better knowledge and medical service for
children in high-industrial countries only but will also help to improve drug
treatment especially for those children in the developing countries. Intense interna-
tional networking initiatives could be very helpful to come closer to achieve the
goal of better medicines for all children worldwide.
Truly the time should be over, in which drug treatment was everybody’s business
with the consequence that this everybody’s business is frequently nobody’s business
(Shirkey 1975).
Marburg, Germany Hannsjörg W. Seyberth

Stockholm, Sweden Anders Rane
Stuttgart/Tübingen, Germany Matthias Schwab
Contents
Part I General Considerations and Methodological Aspects
Basics and Dynamics of Neonatal and Pediatric Pharmacology . . . . . . . . . . . 3

Hannsjörg W. Seyberth and Ralph E. Kauffman
Developmental Pharmacokinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51
Johannes N. van den Anker, Matthias Schwab, and Gregory L. Kearns
Principles of Therapeutic Drug Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Wei Zhao and Evelyne Jacqz-Aigrain
Drug Delivery and Formulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Jörg Breitkreutz and Joachim Boos
Part II Development of Pediatric Medicines
Development of Paediatric Medicines: Concepts and Principles . . . . . . . . . 111

Klaus Rose and Oscar Della Pasqua
Study Design and Simulation Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

Stephanie Läer and Bernd Meibohm
Efficacy Assessment in Paediatric Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

Siri Wang and Pirjo Laitinen-Parkkonen
Safety Assessment in Pediatric Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

Gideon Koren, Abdelbasset Elzagallaai, and Fatma Etwel
vii
viii Contents
Small Sample Approach, and Statistical

and Epidemiological Aspects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181
Martin Offringa and Hanneke van der Lee
Sample Collection, Biobanking, and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

Maurice J. Ahsman, Dick Tibboel, Ron A. A. Mathot,
and Saskia N. de Wildt
Ethical Considerations in Conducting Pediatric Research . . . . . . . . . . . . . . . 219

Michelle Roth-Cline, Jason Gerson, Patricia Bright,
Catherine S. Lee, and Robert M. Nelson
Pediatric Regulatory Initiatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

Steven Hirschfeld and Agnes Saint-Raymond
Part III Specific Pediatric Pharmacology
Fetal Medicine and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

Magnus Westgren
Fetal Risks of Maternal Pharmacotherapy: Identifying Signals . . . . . . . . . 285

Gideon Koren
Antiepileptic Treatment in Pregnant Women: Morphological

and Behavioural Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 295
Torbjörn Tomson and Dina Battino
Preventive Medicines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317

Ulrich Heininger
Postmarketing Surveillance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

Vera Vlahović-Palčevski and Dirk Mentzer
Global Aspects of Drug Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353

Kalle Hoppu and Hans V. Hogerzeil
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 373
Contributors
Maurice J. Ahsman Department of Clinical Pharmacy, Erasmus MC, Rotterdam,

The Netherlands
Dina Battino Department of Neurophysiopathology and Epilepsy Centre, IRCCS

Foundation Carlo Besta, Neurological Institute, Milan, Italy
Joachim Boos Klinik und Poliklinik für Kinder- und Jugendmedizin, Westfälische
Wilhems-Universität, 48149 Münster, Germany
Jörg Breitkreutz Institut für Pharmazeutische Technologie und Biopharmazie,

Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf,
Germany
joerg.breitkreutz@uni-duesseldorf.de
Patricia Bright U.S. Department of Health and Human Services, Food and Drug
Administration, Office of the Commissioner, Office of Pediatric Therapeutics,
Silver Spring, MD 2011, USA
Oscar Della Pasqua Division of Pharmacology, Amsterdam Center for Drug

Research, Leiden University, Einsteinweg 55, P.O. Box 9503, 2300 RA Leiden,
The Netherlands; Clinical Pharmacology & Discovery Medicine,
GlaxoSmithKline R&D, Stockley Park, Uxbridge, UB11 1BT, United Kingdom
odp72514@gsk.com
Saskia N. de Wildt Intensive Care and Department of Pediatric Surgery, Erasmus

MC Sophia Children’s Hospital, Dr. Molewaterplein 60, 3015 GJ Rotterdam, The
Netherlands
s.dewildt@erasmusmc.nl
Abdelbasset Elzagallaai Division of Clinical Pharmacology and Toxicology,

Hospital for Sick Children, University Avenue 555, Toronto M5G 1X8, ON, Canada
ix
x Contributors
Fatma Etwel Division of Clinical Pharmacology and Toxicology, Hospital for

Sick Children, University Avenue 555, Toronto M5G 1X8, ON, Canada
Jason Gerson U.S. Department of Health and Human Services, Food and Drug
Ulrich Heininger Universitäts-Kinderspital beider Basel (UKBB), Postfach, CH-

4005 Basel, Switzerland
Ulrich.Heininger@ukbb.ch
Steven Hirschfeld National Children’s Study Eunice Kennedy Shriver, National

Institute of Child Health and Human Development, 31 Center Drive, Room 2A03,
MSC 2425, Bethesda, MD 20892, USA
hirschfs@mail.nih.gov
Hans V. Hogerzeil Essential Medicines and Pharmaceutical Policies, World

Health Organization, 1211 Geneva 27, Switzerland
Kalle Hoppu Poison Information Centre, Helsinki University Central Hospital

and Hospital for Children and Adolescents, Institute for Clinical Sciences,
University of Helsinki, P.O. Box 790 (Tukholmankatu 17), 00029 HUS
(Helsinki), Finland
kalle.hoppu@hus.fi
Evelyne Jacqz-Aigrain Department of Pediatric Pharmacology and

Pharmacogenetics, Clinical Investigation Center, CIC Inserm 9202, French
network of Pediatric Investigation Centers (CICPaed), Hôpital Robert Debré, 48
Boulevard Sérurier, 75935 Paris, France
evelyne.jacqz-aigrain@rdb.aphp.fr
Ralph E. Kauffman Division of Clinical Pharmacology and Medical Toxicology,

The Children’s Mercy Hospitals and Clinics, University of Missouri at Kansas City,
2401 Gillham Road, Kansas City, MO 64108, USA
Gregory L. Kearns Division of Pediatric Pharmacology and Medical Toxicology,

Department of Medical Research, Children’s Mercy Hospital, Kansas City, MO, USA
Gideon Koren The Motherisk Program, Division of Clinical Pharmacology and

Toxicology, Hospital for Sick Children, University Avenue 555, Toronto M5G
1X8, ON, Canada
gidiup_2000@yahoo.com
Contributors xi
Stephanie Läer Department of Clinical Pharmacy and Pharmacotherapy, Heinrich-

Heine-University of Düsseldorf, Universitätsstrasse 1, 40225 Düsseldorf, Germany
stephanie.laeer@uni-duesseldorf.de
Pirjo Laitinen-Parkkonen Health Care and Social Services, City of Hyvinkää,

Suutarinkatu 2 C, 05801 Hyvinkää, Finland
Catherine S. Lee U.S. Department of Health and Human Services, Food and Drug
Ron A.A. Mathot Department of Clinical Pharmacy, Erasmus MC, Rotterdam,

The Netherlands
Bernd Meibohm College of Pharmacy, University of Tennessee Health Science

Center, 874 Union Avenue, Rm. 5p, Memphis, TN 38163, USA
Dirk Mentzer Paul-Ehrlich-Institut, Referate Arzneimittelsicherheit, Paul-Ehrlich-

Str. 51-59, 63225 Langen, Germany
Robert M. Nelson U.S. Department of Health and Human Services, Food and
Drug Administration, Office of the Commissioner, Office of Pediatric Therapeutics,
Robert.Nelson@fda.hhs.gov
Martin Offringa Department of Paediatric Clinical Epidemiology, Emma

Children’s Hospital, Academic Medical Centre, University of Amsterdam,
Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
m.offringa@amc.uva.nl
Klaus Rose klausrose Consulting Pediatric Drug Development & More,

Birsstrasse 16, 4052 Basel, Switzerland
rose@granzer.biz
Michelle Roth-Cline U.S. Department of Health and Human Services, Food and
Drug Administration, Office of the Commissioner, Office of Pediatric Therapeutics,
Agnes Saint-Raymond Scientific Advice, Paediatrics, and Orphan Drug Sector,

European Medicines Agency, 7 Westferry Circus, Canary Wharf, London E14
4HB, United Kingdom
xii Contributors
Matthias Schwab Dr. Margarete Fischer-Bosch-Institute of Clinical Pharma-

cology, Auerbachstrasse 112, 70376 Stuttgart, Germany; Department of Clinical
Pharmacology, Institute of Experimental and Clinical Pharmacology and
Toxicology, University Hospital, Tübingen, Germany
Hannsjörg W. Seyberth Klinik für Kinder- und Jugendmedizin, Philipps-Universität

Marburg, Baldingerstraße, 35043 Marburg, Germany; Present address: Lazarettgarten
23, 76829 Landau, Germany
seyberth@staff.uni-marburg.de
Dick Tibboel Intensive Care and Department of Pediatric Surgery, Erasmus

MC Sophia Children’s Hospital, Dr. Molewaterplein 60, 3015 GJ Rotterdam,
The Netherlands
Torbjörn Tomson Department of Clinical Neuroscience, Karolinska Institutet,

S-171 76 Stockholm, Sweden
torbjorn.tomson@karolinska.se
Johannes N. van den Anker Division of Pediatric Clinical Pharmacology,

Department of Pediatrics, Children’s National Medical Center, 111 Michigan
Avenue, NW, Washington, DC 20010, USA
jvandena@cnmc.org
Hanneke van der Lee Department of Paediatric Clinical Epidemiology, Emma

Children’s Hospital, Academic Medical Centre, University of Amsterdam,
Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
Vera Vlahović-Palčevski Department for Clinical Pharmacology, University of

Rijeka Medical School, University Hospital Center Rijeka, Krešimirova 42, 51000
Rijeka, Croatia
vvlahovic@inet.hr
Siri Wang Norwegian Medicines Agency, Tønsberg Hospital Pharmacy, Sven

Oftedalsvei 6, N-0950 Oslo, Norway
siri.wang@noma.no
Magnus Westgren Division of Obstetrics and Gynecology, Department of Clinical

Science, Intervention and Technology, Centre for Fetal Medicine, Karolinska
University Hospital, Karolinska Institutet, S-141 86 Stockholm, Sweden
magnus.westgren@ki.se
Wei Zhao Department of Pediatric Pharmacology and Pharmacogenetics, Clinical

Investigation Center, CIC Inserm 9202, French network of Pediatric Investigation
Centers (CICPaed), Hôpital Robert Debré, 48 Boulevard Sérurier, 75935 Paris,
France
Part I
General Considerations and
Methodological Aspects
Basics and Dynamics of Neonatal and Pediatric
Pharmacology
Hannsj€
org W. Seyberth and Ralph E. Kauffman
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2 Classification of the Pediatric Population . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
3 Description of the Five Relevant Periods of Development, Their Typical Features,
Common Health Problems, and the Impact on Pediatric Pharmacotherapy . . . . . . . . . . . . . . . 7
3.1 The Preterm Newborn: Period of Survival . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.2 The Newborn Term Infant: Period of Adaptation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
3.3 The Infant and Toddler: Period of Rapid Growth and Physiological Maturation . . . 24
3.4 The Child: Period of Language, Socialization, and Continued Growth . . . . . . . . . . . . . 28
3.5 The Adolescent: Period of Final Growth and Reproductive Maturation . . . . . . . . . . . . 32
4 Future Directions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.1 Appropriate Tools for Assessment of Drug Action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.2 Appropriate Animals and Cell Models . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
4.3 Appropriate Methods for Long-Term Safety Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40
Abstract Understanding the role of ontogeny in the disposition and actions of

medicines is the most fundamental prerequisite for safe and effective pharmaco-
therapeutics in the pediatric population. The maturational process represents a contin-
uum of growth, differentiation, and development, which extends from the very small
preterm newborn infant through childhood, adolescence, and to young adulthood.
H.W. Seyberth (*)

Klinik fur Kinder- und Jugendmedizin, Philipps-Universit€at Marburg, Baldingerstraße,
35043 Marburg, Germany
Present address:
Lazarettgarten 23, 76829 Landau, Germany
e-mail: seyberth@staff.uni-marburg.de
R.E. Kauffman
Division of Clinical Pharmacology and Medical Toxicology, The Children’s Mercy Hospitals and
Clinics, University of Missouri at Kansas City, 2401 Gillham Road, Kansas City, MO 64108, USA
H.W. Seyberth et al. (eds.), Pediatric Clinical Pharmacology, 3

Handbook of Experimental Pharmacology 205,
DOI 10.1007/978-3-642-20195-0_1, # Springer-Verlag Berlin Heidelberg 2011
4 H.W. Seyberth and R.E. Kauffman
Developmental changes in physiology and, consequently, in pharmacology

influence the efficacy, toxicity, and dosing regimen of medicines. Relevant periods
of development are characterized by changes in body composition and proportion,
developmental changes of physiology with pathophysiology, exposure to unique
safety hazards, changes in drug disposition by major organs of metabolism and
elimination, ontogeny of drug targets (e.g., enzymes, transporters, receptors, and
channels), and environmental influences. These developmental components that
result in critical windows of development of immature organ systems that may lead
to permanent effects later in life interact in a complex, nonlinear fashion.
The ontogeny of these physiologic processes provides the key to understanding
the added dimension of development that defines the essential differences between
children and adults. A basic understanding of the developmental dynamics in
pediatric pharmacology is also essential to delineating the future directions and
priority areas of pediatric drug research and development.
Keywords Ontogeny • Pediatric population • Classification • Maturation •

Developmental changes • Pharmacokinetics • Pharmacodynamics • Neonatal
pharmacology • Pediatric pharmacotherapeutics • Long-term safety
Abbreviations
ADHD Attention-deficit/hyperactivity disorder

ACE Angiotensin-converting enzyme
ACh Acetylcholine
AN Anorexia nervosa
ATR Angiotensin receptor
BN Bulimia nervosa
CDL Chronic lung disease
Clsys Systemic clearance
CYP CytochromeP450
DCT Distal convoluted tubule
GABA Gamma-aminobutyric acid
GnRH Gonadotropin-releasing hormone
HPG Hypothalamic–pituitary–gonadal
KCC2 Potassium-chloride cotransporter type 2
nAChRs Nicotine acetylcholine receptors
NAT N-Acetyltransferase
NEC Necrotizing enterocolitis
NCCT Sodium-chloride cotransporter
NKCC1 Sodium-potassium-2-chloride cotransporter type 1
PDA Patent ductus arteriosus
PDE Phosphodiesterase
P-gp P-glycoprotein
Basics and Dynamics of Neonatal and Pediatric Pharmacology 5
RDS Respiratory distress syndrome

ROP Retinopathy of prematurity
SIDS Sudden infant death syndrome
SLT Salt-losing tubular disorder
SSRI’s Selective serotonin reuptake inhibitors
TDM Therapeutic drug level monitoring
UGT Uridine diphosphate glucuronosyltransferase
V(d) Volume of distribution
1 Introduction
A safe and effective medication for children requires a fundamental understanding

and integration of the role of ontogeny in the disposition and actions of medicines.
As the most fundamental prerequisite, one has to consider the basic principle that
children are not small adults!
The German-American and father of American pediatrics, Abraham Jacobi
(1830–1919), recognized the importance of and the need for age-appropriate
pharmacotherapy when he emphasized: “Pediatrics does not deal with miniature
men and women, with reduced doses and the same class of disease in smaller
bodies, but . . . has its own independent range and horizon” (Kearns et al. 2003).
Along that line of argumentation some years later the German pioneer of pediatric
pharmacology, Rudolf Fischl (1862–1942), wrote: “Die Therapie des Kindesalters
bedeutet nicht lediglich eine Restriktion der Behandlung der Erwachsenen, sondern
baut sich auf genaue Kenntnisse der Physiologie dieser Lebensepoche auf” (Fischl
1902). Moreover, he stated: “Viel Ungl€ uck hat schon die Mathematik in der Medizin
angerichtet, und eine einfache Berechnung der sogenannten refrakten Dosen f€ ur
das Kindersalter aus der Gewichtsdifferenz k€ onnen leicht ebenfalls ein solches
anrichten” (Fischl 1902). Harry Shirkey (1916–1995), the well-known American
pharmacist and pediatrician, wrote in his textbook on Pediatric Therapy with other
words: “The long list of dosage rules based on age, body weight or surface and their
respective authors is testimony that no rule is entirely satisfactory in producing an
exact fraction of the known adult dose that is applicable to a particular child”
(Shirkey 1975). This fundamental knowledge of determining the pediatric dosage
of a medicine is even today – 100 years later – often ignored. Thus, as the first step
for a successful approach to pediatric therapeutics, one must appreciate the dif-
ferences among pediatric subpopulations with their typical features and health
problems and the nonlinear and dynamic process of maturation. The ontogeny of
basic physiologic processes provides guideposts for understanding the mechanisms
underlying differences between different developmental stages within the pediatric
and adult populations.
2 Classification of the Pediatric Population
The pediatric population represents a continuum of growth and development, which

extends from the very small preterm newborn infant through childhood, adoles-
cence, and to young adulthood (Fig. 1). The internationally agreed (Food and Drug
Administration 2000), and to some extent arbitrary, classification of the pediatric
population is as follows:
– Preterm infants (<37 weeks gestation)
– Term newborn infants (0–28 days)
– Infants and toddlers (>28 days to 23 months)
– Children (2–11 years)
– Adolescents (12 to 16–18 years, depending on the region)
Substantial changes in body composition and proportions accompany growth
and development. Embedded within this continuum of growth and development
is substantial individual variation. Developmental changes in physiology and,
consequently, in pharmacology influence the efficacy, toxicity, and dosing regimen
of medicines (posology) used in children. It is, therefore, important to review
characteristics of the relevant periods of development from birth, through adoles-
cence, to adulthood.
Fig. 1 Five stages of development. The pediatric population extends from the preterm and term
newborn infant through childhood, and adolescence, or even to young adulthood. Each period of
development has its own very specific characteristics, such as period of survival, period of
adaptation, period of rapid growth and physiological maturation, period of language, socialization,
and continued growth, and period of final growth and reproductive maturation
3 Description of the Five Relevant Periods of Development,

Their Typical Features, Common Health Problems,
and the Impact on Pediatric Pharmacotherapy
3.1 The Preterm Newborn: Period of Survival
3.1.1 Body Composition and Proportion
Body composition correlates with both gestational and postnatal age, and it con-
tinues to change significantly during the first year of life (Ahmad et al. 2010; Ellis
2000; Fomon and Nelson 2002). High body water content and extracellular/intra-
cellular water ratio as well as very low body fat and muscle mass in the preterm
infant are important contributors to altered volumes of distribution (V(d)) of
hydrophilic and lipophilic medicines or highly tissue-bound drugs such as the
cardiac glycosides. For example, the larger total body water content of the newborn
infant (approximately 80% as compared with 60% of body weight by 5 months of
age) results in a larger mg/kg-loading dose of water-soluble medicines, such as the
aminoglycosides (Pacifici 2009).
The relatively large head circumference and cranial volume is the leading
characteristic of the body proportion from the very preterm newborn to the older
infant and toddler. Relatively large brain weight and cerebral blood flow, limited
plasma protein binding capacity, as well as increased blood–brain barrier perme-
ability all predispose the CNS to higher concentrations of administered medicines
than later in life (Strolin Benedetti et al. 2005).
Likewise, increased skin permeability needs to be considered whenever a medi-
cine is applied on the skin. Increased dermal absorption may increase risk of
adverse effects as with antibacterial agents such as alcohol and hexachlorophene
solution (Stewart and Hampton 1987) or provide an option for painless and nonin-
vasive transdermal drug delivery in preterm newborns as with caffeine for apnea
(Barrett and Rutter 1994).
3.1.2 Developmental Changes of Physiology with Their Pathophysiology

and Safety Hazards
The Very Preterm Newborn (<30 Weeks of Gestation)
The very (extremely) preterm newborn around the 22–23 weeks of gestation is
at the limit of viability because the incompletely developed complex pulmonary–
cardiovascular system is not prepared to function well in the extrauterine environ-
ment, even with intensive support. The multiple hazards are as follows:
– Respiratory distress syndrome (RDS)

Before primitive alveoli have formed and surfactant production has begun, the
lung cannot adequately function as an organ of gas exchange. At an early and
intermediate stage of pulmonary maturation, the very preterm newborn requires
administration of exogenous surfactant and prolonged mechanical ventilation to
prevent and/or treat severe RDS. These treatments, along with lung immaturity,
are commonly associated with development of chronic lung disease of prematu-
rity (Stevens et al. 2007).
– Persistent fetal circulation
In this condition, the transitional from fetal to neonatal circulation is charac-
terized by pulmonary hypertension and patent ductus arteriosus (PDA), which
are responsible for marked right to left circulatory shunting and hypoxia.
– Incomplete cerebral autoregulation
Impaired or completely missing cerebral autoregulation is a risk factor for
intraventricular hemorrhage with parenchymal brain injury and posthemorrhagic
complications later in life such as cerebral palsy, hydrocephalus, and cognitive
deficits (Szabó et al. 2009).
– Necrotizing enterocolitis (NEC)
Immaturity of the gastrointestinal tract and immune system predisposes the very
preterm infant to NEC with life-threatening complications including fulminate
septic shock (Neu 2007; Thompson and Bizzarro 2008).
The Late Preterm Newborn (31–36 Weeks of Gestation)
At this stage, the infant is rarely in a life-threatening situation, but still is at risk for a
series of serious health problems related to immaturity of several organ systems.
These include:
– Transient tachypnea
Lack of clearance of lung fluid and relative deficiency of pulmonary surfactant
may cause transient tachypnea and RDS (Raju et al. 2006).
– Relapse into fetal circulation
Partial relapse into fetal circulation may lead to pulmonary hypertension of the
newborn. This condition may be associated with sepsis or sometimes with
maternal use of selective serotonin reuptake inhibitors (SSRIs) (Konduri and
Kim 2009; Koren and Boucher 2009; Ramachandrappa and Jain 2009).
– Temparature instability and apnea
CNS immaturity may lead to poor temperature control (Raju et al. 2006) and
failure of respiratory control with central apnea (Hunt 2006).
– Peristaltic dysfunction
Immaturity of the gastrointestinal tract may lead to feeding problems related to
peristaltic dysfunction and failure of sphincter control in the esophagus, stom-
ach, and intestines (Lebenthal and Lebenthal 1999; Neu 2007).
– Jaundice and hypoglycemia

Prolonged hyperbilirubinemia and hypoglycemia are risk factors for brain injury
(Raju et al. 2006).
– Susceptibility to infection
An incompetent (naı̈ve) immune system increases susceptibility to infection and
predisposes the infant to sepsis (Clapp 2006).
3.1.3 Major Organs of Metabolism and Elimination
Developmental immaturity has a major impact on drug disposition in preterm

infants. Changes in the V(d) have already been mentioned in the context of body
composition. The next most important pharmacokinetic factor for pediatric dosing
is reduced systemic clearance (Clsys) due to immaturity of the liver and kidneys, the
most important organs involved in the process of drug metabolism and elimination.
The relatively large Vd and reduced Clsys in neonates commonly require a higher
loading dose and lower maintenance dose of many drugs (Bartelink et al. 2006).
The gray baby syndrome, a fatal cardiovascular collapse, is a frequently cited his-
torical example of drug toxicity on the basis of immature hepatic glucuronidation of
chloramphenicol leading to supratherapeutic systemic concentrations when infants
were given doses used in older children (Asmar and Abdel-Haq 2005).
Hepatic Metabolism
Because of quantitative and qualitative differences in hepatic drug metabolism,

medicines that are primarily metabolized by the liver may need to be administered
in reduced doses until the age of about 2 months (Alcorn and McNamara 2002;
Allegaert et al. 2007; Anderson and Lynn 2009; Bartelink et al. 2006). Enzymes
most commonly involved in drug metabolism are those of the cytochrome P450
(CYP) family (phase I reactions) and the uridine diphosphate glucuronosyltrans-
ferase (UGT), sulfotransferase, glutathione-S-transferase, and N-acetyltransferase
(NAT) families (phase II reactions). Each of the specific isozymes within a family
matures at different rates during the first several years of life. The effect on
metabolism of a specific medication depends on the dominant enzymatic pathway(s)
responsible for metabolism of the drug. Several studies have been performed with
medicines, which are frequently used in neonatology. Indomethacin is a substrate
for CYP2C9 (Koukouritaki et al. 2004; Rodrigues AD 2005); phenobarbital is also
a substrate for CYP2C9 in addition to CYP2C19 (Goto et al. 2007; L€oscher et al.
2009); caffeine is metabolized by CYP1A2 and NAT2 (Pons et al. 1989); and
morphine is a specific substrate for UGT2B7 (Coffman et al. 1997). These
medicines function as markers for hepatic metabolic activity, which is low relative
to older children and adults, leading to reduced total clearance of these drugs during
the neonatal period (al-Alaiyan et al. 2001; Battino et al. 1995; Hartley et al. 1994;
Yaffe et al. 1980).
A qualitative difference in hepatic drug metabolism is exemplified by the

different metabolite profile of theophylline in newborns with the attendant risk of
caffeine toxicity (Bory et al. 1979; Lowry et al. 2001). Theophylline and caffeine
are frequenty used to treat apnea of prematurity. In contrast to adults, in preterm
newborns caffeine is a biotransformation product of theophylline and may accumu-
late to toxic levels with chronic theophylline dosing. To avoid this complication,
caffeine is the preferred methylxanthine to treat apnea of prematurity. This reduces
the risk of methylxanthine toxicity and avoids the need for routine therapeutic drug
level monitoring (TDM) (Charles et al. 2008; Natarajan et al. 2007; Steer and
Henderson-Smart 2000).
Renal Elimination
At birth renal function is rather low, with a GFR down to 1 ml/min/kg, and does
not approach adult levels before the age of 6–12 months (Alcorn and McNamara
2002). Tubular secretion matures more slowly and full renal function is reached
at approximately 2–3 years of age (Fawer et al. 1979; Fettermann et al. 1965).
Delayed maturation of tubular reabsorption leads to glomerulotubular imbalance
with the risk of salt and water wasting (Alcorn and McNamara 2002; Bartelink
et al. 2006; Celsi and Aperia 1993). On the positive side, the decreased ability to
concentrate aminoglycosides in the tubular epithelium contributes to decreased
nephrotoxicity of aminoglycosides in newborns (Fleck and Br€aunlich 1995;
McCracken 1986).
Thus, it is not surprising that furosemide, which is mainly excreted as a substrate
of the PAH transport pathway unchanged in the urine, has a prolonged plasma half-
life (often exceeding 24 h) and a very low renal clearance particularly in the very
preterm newborns (Mirochnick et al. 1988; Peterson et al. 1980). Similarly, weak
organic acids such as penicillins and cephalorins, which are frequently used in
newborns, also have very low total clearances in preterm infants. The kidney almost
exclusively excretes these medicines by an active tubular organic anion transport
system, which has 20–30% of adult capacity at birth and approaches adult capacity
at approximately 7–8 months (Alcorn and McNamara 2002).
3.1.4 Ontogeny of Drug Targets in the Perinatal Period
During the perinatal period many fundamental changes take place, which are
unique to the newborn and are not observed again during infancy, childhood, and
adolescence. To describe all these changes, which certainly have an impact on drug
targets, would be far beyond the scope of this subsection. Thus, only selected
aspects, where substantive progress is relevant to pediatric pharmacology, includ-
ing molecular pharmacodynamics and pharmacogenetics, are discussed.
Receptors/Binding Sites
– Adrenergic receptors
The ontogeny of drug–receptor interactions, particularly of the adrenergic and
cholinergic systems, has been of long-standing interest to pediatric pharmaco-
logists (Boréus 1972). However, methods for isolation of homogeneous cells
from organs of the fetus or the newborn ensuring that the cells and receptors
have not been altered during isolation and purification have not been adequately
developed (Whitsett et al. 1982). Nevertheless, there is ample direct and indirect
experimental evidence of ontogenic regulation of receptor number and function.
In the newborn rat brain, there are an increased number of b-adrenergic receptors
during the first weeks of life, while at the same time the number of a-adrenergic
receptors is declining after an initial rise in the rat brain shortly after birth
(Whitsett et al. 1982). Unfortunately, due to methodological reasons, similar
data in human tissue are often missing. Thus, more readily accessible circulating
nucleated blood cells, e.g., leukocytes, have been used with the assumption
that they may reflect the status of adrenergic receptors in the actual target
organ of interest (Fraser et al. 1981). Decreased b-adrenergic receptor sites
have been described in human cord blood neutrophils (PMN) of infants vagi-
nally delivered at term (Roan and Galant 1982). These findings may reflect
ontogenic differences between the neonatal and adult PMN. However, the effect
of increasing catecholamine secretion during the stress of delivery resulting in
downregulation of the b-adrenergic receptors cannot be ruled out.
More recent molecular pharmacology studies in the postnatal rat devoted to the
ontogenesis of b-adrenergic signaling indicate that, in contrast to the receptor
downregulation and desensitization of b-adrenergic receptors observed in the
adult, the numbers and responsiveness of b-adrenergic receptors increase in most
tissues of the immature organism in response to prolonged treatment with betami-
metics during the postnatal period. This developmental stage of the rat approxi-
mately correlates with the mid-to-late second and early third trimester of human
gestation (Slotkin et al. 2003). The process of downregulation and desensitization
are not inherent properties, but rather acquired during the above-mentioned vul-
nerable time interval when pregnant women may be treated with betamimetics for
preterm labor. Thus, intrauterine overstimulation with betamimetics during this
critical period of prenatal development can induce a permanent shift in the balance
of adrenergic-to-cholinergic tone with the risk of inducing functional and behav-
ioral teratogenesis. This is a currently offered working hypothesis in an attempt to
explain the association of prolonged (3–4 weeks) betamimetic treatment for
tocolysis and bronchodilatation of the mother with increases in functional and
behavioral disorders, including psychiatric disorders (e.g., autism), poor cognitive
and motor function, and school performance as well as changes in blood pressure
(e.g., hypertension) in the offspring (Witter et al. 2009).
– Prostanoid receptors
Prostanoids are abundantly generated throughout the perinatal period. They are
thought to be key players in the regulation of ductus arteriosus tone and in the
autoregulation of blood flow to the brain and retina as well as to the renal and
splanchnic vascular beds (Seyberth and K€
uhl 1988; Smith 1998; Wright et al. 2001).
The rapid changes in vascular physiology during postnatal life are not only
accomplished by rapid changes of the synthesis and metabolism of these
autacoids, but also by rapid adjustments in the turnover of prostanoid receptor
expression. This has been particularly well studied in the regulation of ductus
arteriosus tone (Smith 1998).
In utero, the main factors maintaining patency of the ductus arteriosus are
low oxygen tension and high levels of PGE2 and PGI2 (Fig. 2), which are
acting through prostanoid EP4 and IP receptors (Smith 1998; Smith and McGrath
1994; Leonhardt et al. 2003; Wright et al. 2001). Both receptors are coupled to
adenylate cyclase (Boie et al. 1994; Honda et al. 1993). cAMP generated by this
enzyme is considered to be the main intracellular second messenger involved in
smooth muscle relaxation, which is consistent with the potent vasodilator effect
PGE2 and PGI2 on the ductus. After birth, increased ductal oxygen tension and
a fall of prostanoid levels, which is accompanied by a marked reduction of
Fig. 2 Perinatal switch of ductus arteiosus from vasodilation to vasoconstriction. In utero, and to
some extent in the pretem newborn, patency of the ductus arteriosus is maintained by high levels
of PGE2 and PGI2 in addition to low oxygen tension. The potent vasodilator effect PGE2 and PGI2 on
the ductus is mediated through PGE2 and PGI2 receptors, EP4 and IP, respectively, by increasing
cAMP. cAMP is considered to be the main intracellular second messenger involved in smooth
muscle relaxation of the ductus. Postnatal increase in arterial PaO2 plays an important role in
functional closure of the ductus, which starts with oxygen-induced inhibition of O2-sensitive
potassium channels. This leads to smooth muscle cell depolarization and consequently to increased
calcium influx through voltage-dependent L-type calcium channels. In parallel with advancing
gestation, smooth muscle phosphodiesterase (PDE) isoforms in the ductus are increasingly expressed
leading to decreased intracellular cAMP, thus supporting the shift from dilatation to constriction of
the ductus arteriosus. PDE inhibitors such as milrinone, however, can prevent this shift
prostanoid receptor expression, induces closure, thus promoting contraction of

the ductus arteriosus (Bouayad et al. 2001; Smith et al. 2001; Wright et al. 2001).
Preterm infants with RDS and mechanically ventilated lungs are prone to
develop a symptomatic PDA on the basis of persistent PGE2 and PGI2 release
probably from the ventilated lung (Smith 1998; Seyberth et al. 1984). Thus, at
the present time the most appropriate pharmacological intervention is the treat-
ment with prostaglandin synthesis inhibitors (Fig. 2), such as indomethacin
(Hammerman et al. 2008; Leonhardt and Seyberth 2003; Ohlsson et al. 2008).
However, this systemic inhibition of endogenous prostanoid synthesis has some
negative consequences. Firstly, all prostanoid effects are inhibited including
those of TxA2 and PGF2a, which do have additional vasoconstrictor potential
via specific receptors on the ductus. Secondly, inhibition of all endogenously
synthesized prostanoids has negative effects on a variety of physiological and
protective functions of blood cells and organs such as platelets, kidney, and
intestinal tract (Seyberth and K€ uhl 1988; Smith 1998; Wright et al. 2001).
A potent and selective EP4 receptor antagonist might be a more appropriate
alternative for pharmacologically induced ductal closure (Momma et al. 2005b;
Smith 1998; Wright et al. 2001). A selective EP4 receptor agonist, on the other
hand, could be an ideal tool in maintaining the ductus open in newborns with
ductus-dependent congenital obstructive heart malformations (Momma et al.
2005a; Leonhardt et al. 2003; Smith 1998).
During experimental studies, predominately with fetal lambs, another impor-
tant aspect of clinical relevance has become apparent. With increasing gesta-
tional age, and, certainly after birth, before irreversible anatomic remodeling of
the ductus takes place there is a decreasing ductal sensitivity to vasodilatory
prostanoids. This desensitization is not only accomplished by a reduction of
PGE2 receptor density but also by inhibition of the receptor-coupled mechanism,
which leads to lower intracellular cAMP concentrations (Waleh et al. 2004).
With advancing gestation, smooth muscle phosphodiesterase (PDE) isoforms in
the ductus are increasingly expressed leading to increased cAMP degradation
and decreased intracellular cAMP, thus inducing a shift from dilatation to
constriction of the ductus arteriosus (Liu et al. 2008). This crucial role of these
phosphodiesterases in the regulation of ductal tone needs to be considered when
proposing use of PDE inhibitors such as milrinone for treatment of cardiac failure
in preterm infants (Toyoshima et al. 2006) (Fig. 2). There is good experimental
and clinical evidence that PDE 3 inhibitors prevent closure of the ductus
arteriosus in preterm newborns, thus antagonizing the positive inotropic effect
of these drugs in these infants (Paradisis et al. 2009; Toyoshima et al. 2006).
Channels and Transporters
– Channel maturation and regulation of ductal tone during the perinatal period
Developmental changes of channel activities have been studied during rapid
physiological changes around birth. Besides the prostanoid system complex,
non-PG procontractile pathways are involved in the oxygen-induced functional

closure of the ductus arteriosus. The postnatal increase in arterial PaO2 plays an
important role in active ductal constriction (Fig. 2). This functional closure
of the ductus starts with oxygen-induced inhibition of O2-sensitive potassium
channels, which leads to smooth muscle cell depolarization and consequently to
increased calcium influx through voltage-dependent L-type calcium channels
(Nakanishi et al. 1993; Thébaud et al. 2004; Waleh et al. 2009). In preparation
for extrauterine life, the expression of the calcium channels starts to increase
during late gestation, while the inhibitory effect of the potassium channels
declines (Clyman et al. 2007; Waleh et al. 2009). Thus, in preterm infants this
maturation of active ductal vasoconstriction has not been fully completed, which
contributes to persistent ductal patency. Since changes in membrane potential
clearly play a critical role in regulating ductal tone, compounds acting at
O2-sensitive potassium channels are promising candidates for pharmacomani-
pulation of the ductus arteriosus after birth in both term and preterm infants
(Smith 1998).
This understanding of the ontogenetic changes in tuning the muscular wall of
the ductus is essential to understanding the mechanism by which chronic in utero
inhibition of prostanoid synthesis is associated with temporary delay or even
prevention of postnatal ductal closure. At the same time, when synthesis of
relaxing prostanoids is inhibited, the expression of the O2-sensitive potassium
channel and calcium L-channel genes in the ductus wall is also reduced. In other
words, the capability of O2-induced ductal constriction has been weakened or
even abolished (Momma et al. 2009; Reese et al. 2009). These experimental
findings have been corroborated by clinical observations. The so-called para-
doxical failure of ductal closure can be induced either after prenatal adminis-
tration of indomethacin for preterm labor or after indomethacin treatment
immediately after birth for prevention of patent ductus (Hammerman et al.
1998; Momma et al. 2009; Norton et al. 1993).
– Channels and transporters involved in transepithelial electrolyte transport
Another field, in which channels and transporters play an important role, is the
transepithelial electrolyte transport in the developing kidney. Tubular reabsorp-
tion of salt and water begins maturing with very dynamic changes during the
perinatal and early postnatal period (Alcorn and McNamara 2002). The so-called
pharmacotyping of inherited hypokalemic salt-losing tubular disorders (SLT)
associated with secondary hyperaldosteronism was extremely helpful in
identifying common targets for mutations and developing interventions by
pharmacologists (Reinalter et al. 2004) (Fig. 3). The furosemide-like SLT with
a loop disorder and the thiazide-like SLT with a distal convoluted tubule (DCT)
disorder are the two major types of SLT (Seyberth 2008). The phenotypes of the
two genetic and the pharmacologically distinct “human knockouts” – defects of
NKCC2 and NCCT – are almost identical, which include, in addition to hypo-
kalemic alkalosis in both of them, polyuria, isosthenuria, and hypercalciuria for
the furosemide type and hypomagnesemia and hypocalciuria for the thiazide
type (Jeck et al. 2005; Peters et al. 2002). Moreover, patients with a loop disorder
Fig. 3 Pharmacologic and genetic targets in transepithelial salt transport in distal tubule. Inherited
hypokalemic salt-losing tubular disorders (SLT) associated with secondary hyperaldosteronism
have common targets for mutations and pharmacological interventions such as the furosemide-
sensitive sodium-potassium-chloride cotransporter (NKCC2) and the thiazide-sensitive sodium-
chloride cotransporter (NCCT). The furosemide-like SLT is primarily a polyuric and
hypercalciuric loop disorder, while the thiazide-like SLT is a distal convoluted tubule (DCT)
disorder, which is characterized by persistent hypomagnesemia and hypocalciuria
do not respond to furosemide but do respond, as expected, to thiazide treatment

(K€ockerling et al. 1996). In contrast, the diuretic response in patients with a DCT
defect is just the opposite (Colussi et al. 2007). The time of clinical presentation is
another major difference between the two tubular disorders (Peters et al. 2002).
While the loop defect presents in utero with fetal polyuria associated with the
development of polyhydramnios and premature birth, the thiazide-like DCT
defect rarely becomes symptomatic before late infancy with hypokalemic alka-
losis as a consequence of a relatively mild salt and water diuresis.
From these experiments of nature one can predict that, in contrast to loop
diuretics, thiazide diuretics are not going to be very efficacious in preterm
infants. The NCCT in the DCT probably is not active and/or not expressed at
that early stage of development. This hypothesis might be supported by the
results of a well-controlled drug study with preterm infants (Green et al. 1983).
While infants receiving furosemide clearly exhibited diuretic activity, the res-
ponse in those given chlorothiazide (20 mg/kg/d) was no different from patients
not given diuretics. Immunohistological studies with renal tissue of very preterm
infants need to be done to prove this hypothesis directly.
Endocrine/Paracrine System and Renal Function
Complex endocrine/paracrine interactions of the renin-angiotensin and the renal

prostanoid system are critically involved in the protection and maintenance of
adequate renal blood perfusion and function. The extreme low blood pressure of the
preterm infant with a mean arterial pressure of about 30 mm Hg makes an effective
filtration pressure highly dependent on the activity of vasoconstrictive angiotensin
II on the one hand and on vasodilatory renal prostanoids on the other hand (Evans
and Moorcraft 1992; Guignard 2002; Prevot et al. 2002; Seyberth et al. 1991). This
well-coordinated vasoconstriction and vasodilatation of the afferent and efferent
glomerular vasculature renders renal function oversensitive to any angiotensin-
converting enzyme (ACE) inhibitor or angiotensin receptor (ATR) antagonist and
prostanoid synthesis inhibitor. Thus, besides their intrinsic potency one cannot
expect any major differences in renal toxicity among ACE inhibitors and ATR
antagonists as well as among prostanoid synthesis inhibitors (FitzGerald and
Patrono 2001; Fr€olich 1997; Guignard 2002; Prevot et al. 2002). As long as one
avoids a prolonged ineffective circulatory volume created by extreme fluid restric-
tion, unnecessary furosemide treatment, and failure of ductal closure (all are
additional stimuli for the renin-angiotensin system), no major renal damage to the
preterm newborn is to be expected (Leonhardt et al. 2004; Seyberth et al. 1983).
Under this condition, even a 10- to 100-fold overdose of indomethacin, caused by
medication error, does not lead to significant deterioration of renal function
(Narayanan et al. 1999; Schuster et al. 1990).
3.1.5 Environment and Critical Windows/Periods of Development

of Immature Organ Systems with Resulting Permanent Effects
on Phenotype
A classical pediatric example of this phenomenon – also sometimes called “pro-

gramming” – is congenital hypothyroidism. If this condition remains undetected
and untreated shortly after birth, it gives rise to lifelong phenotypic changes and
learning difficulties. There is no comparable condition in adulthood because
although hypothyroidism occurs in later life, the central nervous system has ceased
developing. Now we discuss similar effects due to postnatally applied environmen-
tal and/or pharmacological factors.
Pathophysiology of Retinopathy of Prematurity
Retinopathy of prematurity (ROP) is an instructive model to study the long-term

consequences of an interruption of a complex maturation process by premature
birth, particularly if it happens in the middle of a critical time window of develop-
ment. In addition, the course of this vascular disease can be followed under clinical
conditions by repeated inspections of the retina.
ROP remains an important cause of morbidity in the extremely preterm infant.
The significantly improved survival of very premature infants due to advances in
neonatal intensive care during the last decades has decreased mortality of the most
immature newborns, but has not diminished the incidence of ROP worldwide
(Holmstr€ om et al. 2007; Wheatley et al. 2002). ROP is a multifactorial disease of the
developing retinal vasculature under environmental, nutritional, and genetic influ-
ence. The postnatal interruption of a very vulnerable ongoing development around
26 weeks of gestation is a major trigger of this biphasic ocular disease (Hellstr€om
et al. 2009; Kermorvant-Duchemin et al. 2010). During the first ischemic phase after
birth, premature exposure of the retina to hyperoxia induces an arrest in vascular
development with a degeneration of already existing blood vessels. In the second,
vasoproliferative phase the avascular and ischemic retina triggers a compensatory
release of proangiogenic factors. This leads to abnormal, upregulated extraretinal
neovascularization, which may progress to retinal detachment and finally to blind-
ness. Basically, ROP is the result of an unbalanced activity of various proangiogenic
(such as VEGF and IGF1) and antiangiogenic (such as thrombospondin-1) factors,
interacting with protective effects of nutritional factors (such as docosahexaenoic
acid), and cytotoxic effects of oxidative and nitro-oxidative stress-dependent
mediators generated from interaction of trans-arachidonic acid with the nitrogen
dioxide radical or its precursors (Balazy and Chemtob 2008; Kermorvant-Duchemin
et al. 2010). This more complex view on the pathophysiology of ROP, however,
poses new challenges for more rational pharmacologic interventions in the future.
Presently, ROP-induced blindness in children, adolescents, and young adults has to
be considered as a major cause of all visual disorders.
Postnatal Dexamethasone Treatment and Neurological Outcome
Over the past 20 years, corticosteroid use in the preterm infant has fallen in and out
of favor. Steroids were introduced in the 1980s as a mode of preventing and treating
chronic (inflammatory) lung disease (CLD) in the preterm infant population. This
use has been targeted toward low birth weight infants who cannot be weaned off the
ventilator. Dose, duration, and timing of treatment with dexamethasone, the steroid
typically used in NICUs, have varied. Corticosteroids given postnatally are poten-
tially neurotoxic when given in high dose or when used in the first 96 h of life. The
mechanism by which they cause central nervous system damage is unknown, but
may be related to increased risk of periventricular leukomalacia (Levene 2007).
Unfortunately, there is still a need for long-term follow-up and reporting of late
neurological and developmental outcomes, especially among surviving infants, in
those who participated in randomized trials of early postnatal corticosteroid treat-
ment and who have already been sent to school (Doyle et al. 2010).
3.2 The Newborn Term Infant: Period of Adaptation
Body water content and extra/intracellular water ratio remain high as compared to
infants and children. However, with each week of gestational age body fat content
increases when compared with preterm newborns (Ahmad et al. 2010; Ellis 2000;
Fomon and Nelson 2002). Besides relatively large body surface area and head
circumference as well as high permeability of blood–brain barrier and skin, rapid
weight gain is a typical feature during this period of growth and development
(Strolin Benedetti et al. 2005). Greater vulnerability to CNS drug toxicity (e.g.,
local anesthetic agents and opioids) is in part the consequence of the decreased
blood–brain barrier (Latasch and Freye 2002)

and Safety Hazards
Although the term newborn is in a much more mature stage of development than the
preterm newborn, they share several health problems with each other.
Drug Risk of Kernicterus
Icterus neonatorum (physiological jaundice) is certainly a safety hazard for both the
term and preterm newborn. It is the result of increased bilirubin production follow-
ing postnatal breakdown of fetal red blood cells combined with transient limitation
in the conjugation of bilirubin by the liver. Excess circulating unconjugated biliru-
bin is bound to high-affinity acidic binding sites on plasma albumin, from where it
can be displaced by highly bound acidic drugs, such as sulfisoxazole and ibuprofen,
thereby increasing the concentration of free unconjugated bilirubin that may diffuse
into the CNS. This increases the risk of kernicterus in newborn infants (Ahlfors
2004; Gal et al. 2006).
Metabolic Risk During Adaptation
Metabolic instability during the adaptation period shortly after birth may cause
symptomatic hypoglycemia and hypocalcemia with seizures. This adaptive insta-
bility is often an endocrine/metabolic emergency situation leading to hospital
admission (No authors listed 2004). Besides prematurity and intrauterine growth
retardation, gestational diabetes is the most common cause for this neonatal com-
plication (Jain et al. 2008a, b).
Immature Immune System
Immaturity of innate and adaptive immune responses in the perinatal period

predisposes the neonate to increased infectious morbidity and mortality, the most
common complications for all newborns (No authors listed 2004; Satwani et al.
2005).
Increased Susceptibility to Seizure
In addition to the anatomical and metabolic causes of seizures, the newborn brain
is inherently prone to seizures as a consequence of incomplete neuronal matura-
tion processes. The first months of postnatal life are critical for brain development
(Ben-Ari and Holmes 2006; Dubois et al. 2008). At this age cerebral growth and
maturation are intense and are influenced by multiple external stimuli encountered
after birth. Besides dendritic growth and synaptic overproduction (in the gray
matter), which is followed by synaptic pruning, myelination in white matter is
essential for fast impulse conduction and for the structure maturation of functional
networks (Ben-Ari and Holmes 2006; Dubois et al. 2008; Holopainen 2008). It
is thought that at this stage the excitatory activity is enhanced and might contri-
bute to the developing brain’s greater capacity for activity-dependent plasticity.
Myelination is a long nonlinear process that runs from the last trimester of gestation
through the second decade of life with a peak in the first postnatal year. Besides
these structural changes, complex changes in development and function of neuro-
transmitter systems also occur including the postnatal excitatory-to-inhibitory
switch in gamma-aminobutyric acid (GABA) signaling. These functional changes
are described in more detail in “Neurotransmitters, Transporters, and Channels”.
3.2.3 Drug Disposition
Enteral Drug Absorption
Ongoing changes in growth, function, and differentiation of the gastrointestinal

tract occur during adaptation to normal postnatal life. These changes may have
significant effects on systemic delivery of medicines taken by the oral route.
Obviously enteral drug absorption and bioavailability of medicines, which are
administered by mouth, become quite important, as oral dosing is the most common
and convenient route of administration.
In the first hours and days after birth, the intestinal weight and the mucosal mass
almost double to accommodate the change from umbilical cord to oral feeding,
which is similar to the change from parenteral to oral feeding (Commare and
Tappenden 2007). This rapid intestinal growth and functional development is
stimulated by feeding of colostrum, which is rich on peptide growth factors such
as EGF, TGF alpha, and IGF-1. The large amount of secretory IgA in colostrum,
which has a high systemic bioavailability, may also play a role in intestinal
development in addition to providing immunologic protection (Commare and
Tappenden 2007).
Several important examples illustrate the spectrum of dynamic developmental
changes of the gastrointestinal tract during early infancy. These include altered
gastric acid secretion, gastrointestinal transit time, and biliary and pancreatic
exocrine function, all of which can significantly affect drug absorption and bio-
availability of orally administered medicines in the first weeks of life.
Although parietal cells are well developed at term, the gastric pH is neutral at
birth. Decreased capacity for hydrogen ion secretion persists throughout infancy,
particularly represented by decreased acid production following pentogastrin stim-
ulation (Anderson and Lynn 2009; Stewart and Hampton 1987; Strolin Benedetti
et al. 2005). In addition, gastric contents are buffered by frequent feedings and
gastric emptying is delayed. Altogether, these factors significantly influence
the time course of drug absorption and bioavailability of acid-labile proteins and
medicines such as growth factors and penicillins, respectively (Strolin Benedetti
et al. 2005). Gastrointestinal absorption may also be facilitated for macromolecules
such as lactalbumin from human milk or for aminoglycosides in early infancy as a
consequence of the immature gastrointestinal mucosal barrier with increased per-
meability (Axelsson et al. 1989; Bhat and Meny 1984). In contrast, there are also
examples of decreased absorption, such as the absorption of fat-soluble vitamins
(vitamins D and E) in newborn infants probably because of the inadequate bile salt
concentration in the ileum (Strolin Benedetti et al. 2005) or poor lipase hydrolysis
of orally administered esters of a prodrug such as the palmitate ester of chloram-
phenicol (Shankaran and Kauffman 1984). Similarly, one step beyond intestinal
absorption and hepatic uptake, the ester prodrug oseltamivir is only partially
hydrolyzed to the active oseltamivir carboxylate by human carboxylasases. As
the activity of these enzymes is not fully developed in fetuses and young children
(Yang et al. 2009), one has to expect a low systemic bioavailability of the active
metabolite and a low efficacy of this neuraminidase inhibitor in newborn infants
and young children.
Little information regarding the clinical effects of ontogenetic changes of
cytochrome P450 enzymes and transporter proteins such as P-glycoprotein
(P-gp) in the small bowel is available (Johnson and Thomson 2008). Many oral
medicines used in pediatrics are major substrates for intestinal forms of CYP3A.
In duodenal biopsy specimens from pediatric patients aged 2 weeks to 17 years,
CYP3A4 expression and function were continuously increased with age (Johnson
et al. 2001). CYP3A4 was practically absent in the fetal duodenum and was
expressed at relatively low levels in the newborn, indicating a low first-pass
metabolism of pediatric medicines such as erythromycin (Johnson and Thomson
2008). There is also some evidence that expression of the transporter protein P-gp
is very low in the intestines of term infants as compared to young adults (Miki
et al. 2005).
Reduced expression of CYP3A and P-pg in newborns and young children can
result in increased bioavailability of medicines. For example, a study on oral
midazolam in preterm infants showed a higher bioavailability of 49% compared
to 27–36% in children (de Wildt et al. 2002; Johnson and Thomson 2008). How-
ever, the effect of reduced intestinal and hepatic first-pass metabolism on bioavail-
ability can offset several other bioavailability reducing factors such as altered gut
physiology (see above), intraluminal pH, reduced gastric emptying, or intestinal
transit time.
Major Organs of Metabolism and Elimination
Decreased systemic clearances for most medicines are mainly related to immaturity
of hepatic and renal function (Alcorn and McNamara 2002; Rane 2005). Under
normal conditions, parturition triggers the dramatic development of hepatic
metabolism and renal function of the newborn term infant. However, there is
marked variability in the various maturation processes among the individual
drug-metabolizing enzymes and renal excretory functions, which often last over
the whole first year of life. Thus, this situation is a rapidly changing transitional
phase between the state of a newborn and that of an infant and a toddler (Alcorn and
McNamara 2002; Bartelink et al. 2006; Strolin Benedetti et al. 2005). Clearly, at
that early stage of development both genetic polymorphisms and ontogeny have a
major impact on individualized pharmacotherapy (Allegaert et al. 2007).
The Breast-Fed Infant
Under certain circumstances, breast-feeding and maternal pharmacotherapy can

become a neonatal risk. This has been demonstrated by fatal opioid poisoning in
neonates, whose breast-feeding mothers are ultrarapid metabolizers of codeine to
morphine (Madadi et al. 2009). In this situation, the high maternal morphine levels
in breast milk can deliver an excessive morphine load to the low metabolizing
infant, resulting in pharmacologically significant opioid levels. However, in general
with a few exceptions such as bromocriptine, cocaine, ergotamine, or lithium
most maternal medicines are relatively safe for nursing infants (Berlin 2005; Berlin
et al. 2009).
3.2.4 Ontogeny of Drug Targets in the Neonatal and Postnatal Periods
Opioid receptors are not fully developed in the newborn rat – one of the most
appropriate animal models to study the human species – and mature into adulthood
(Freye 1996; Latasch and Freye 2002). A phenomenal increase in opioid binding
sites occurs during maturation. Receptor density varies by brain region, with earlier
development of caudal and later development in rostral parts of the CNS. Earlier
development of opioid receptors in the medulla and pons, where the respiratory
center is located, is consistent with the clinical observations that the mean plasma
concentration of morphine that induces respiratory depression is in all pediatric age
groups including the newborns in the same range, while the mean blood level to
suppress pain is – with some overlap – about four to five times higher in newborns
and young infants as compared to older infants and children (Bouwmeester et al.
2003; Lynn et al. 1993; Olkkola et al. 1988). These pharmacological differences
of opioids in newborns, if neglected, may be a source of adverse drug reactions
(e.g., respiratory depression) when attempting to provide rapidly effective opioid

analgesia in newborns.
Neurotransmitters, Transporters, and Channels
The present understanding of seizures in the developing brain is derived from

animal models. Experimental models provide only a limited view of the com-
plexity of clinical data; however, the electrophysiological, molecular, and
anatomical features of seizures in the developing brain can usually transcend
interspecies differences (Ben-Ari and Holmes 2006). In addition, during the early
postnatal period, a time when the immature brain is highly susceptible to seizures,
GABA exerts a paradoxical excitatory action in all animal species, including
primates.
The mechanism of increased excitability of the immature brain is basically
described as follows (Ben-Ari and Holmes 2006; Ben-Ari et al. 2007): During the
early postnatal period, at a time when the immature brain is highly susceptible to
seizures, GABA, which in the adult brain is the primary inhibitory neurotransmitter,
exerts paradoxical excitatory action. GABA is initially excitatory because of
a larger intracellular concentration of chloride in immature neurons compared
to mature neurons. The shift from a depolarizing to a hyperpolarizing chloride
current is mediated by an active sodium-potassium-2-chloride cotransporter type 1
(NKCC1) that facilitates the accumulation of chloride in neurons and by a delayed
expression of a neuron-specific potassium-chloride cotransporter type 2 (KCC2)
that extrudes chloride to establish adult concentrations of intracellular chloride. The
depolarization by GABA of immature neurons is sufficient to generate sodium
action potentials and to activate voltage-dependent calcium channels, leading to a
large influx of calcium that in turn triggers long-term changes of synaptic efficacy.
The synergistic action of GABA and calcium channels is unique to the developing
brain and has many consequences on the impact of GABAergic synapses, such as
seizure susceptibility. In addition, agents that interfere with the transport of chloride
exert an antiepileptogenic action. With maturation, there is increasing function of
KCC2 and decreasing function of NKCC1, which explain the declining strength of
depolarization with age. For the clinical consequences of these ontogenetic changes
in early infancy, see “Seizures”.
3.2.5 Environment and Critical Periods/Windows of Development

of Immature Organ Systems with Resulting Permanent Effects
Two examples that demonstrate the sensitivity of time windows of the brain
maturation and neuronal plasticity are presented.
Neonatal Painful Injuries and Their Long-Term Effects on Pain Response

Later in Life is an Appropriate Example in This Context
The evidence that untreated or insufficiently treated pain in neonates and infants
results in long-term adverse consequences (e.g., hyperalgesia) stems from several
well-planned studies such as the randomized clinical trial on the effect of neonatal
circumcision with and without a topical local anesthetic on pain response during
subsequent vaccination 4–6 months later (Taddio et al. 1997). Even in extremely
preterm infants, painful procedures during intensive care and surgery have an
impact on somatosensory perception later in life (Walker et al. 2009; Hohmeister
et al. 2010). Thus, the immature CNS is a challenge when managing pain treatment
in infants with an emphasis on the need for a longer term view (Fitzgerald and
Walker 2009).
Inappropriate Treatment of Neonatal Seizures Also Has Long-Term Effects

on Brain Development and Function
Microcephaly, postnatal epilepsy, developmental delay, cerebral palsy, and

behavioral problems are commonly associated with repeated or prolonged and
electroencephalographically proven neonatal seizures (Glass and Wirrell 2009;
Holmes 2009). While separating the consequences of seizure from consequences
of the underlying etiology is clinically quite difficult, there is a considerable
body of evidence from animal studies, which support the hypothesis that neo-
natal seizures can adversely interfere with the highly regulated developmental
processes of the brain (Holmes 2009; Holopainen 2008). These animal data
indicate that neonatal seizures, in contrast to seizures in a mature stage of the
brain with fixed circuitry, are followed by long-lasting and persistent sequelae.
These detrimental consequences are caused by alterations of developmental
programs rather than by neuronal cell death, as occurs in adults. Decreases in
neurogenesis and sprouting of mossy fibers, long-standing changes in signaling,
and finally failure to construct efficient networks are the consequences of
these alterations. These anatomic and physiologic changes correlate well with
behavioral dysfunction and permanent handicaps later in life (Holmes 2009;
Holopainen 2008).
All these reports provide good evidence for the need to prevent seizures in
neonates. However, highly effective and safe anticonvulsive medicines for neonatal
seizures with appropriate target- and age-specificity are not currently available,
although some promising drug targets for the immature brain have been proposed
(Glass and Wirrell 2009; Sankar and Painter 2005). The most commonly used first-
line anticonvulsants, phenobarbital and phenytoin, are borderline effective and
potentially neurotoxic for the developing brain (Bittigau et al. 2003).
3.3 The Infant and Toddler: Period of Rapid Growth

and Physiological Maturation
At this stage of development young children are still rapidly growing. Body weight
typically doubles by 5 months of age and triples by 1 year. By the first birthday,
body length and surface area increase by 50 and 200%, respectively. During this
period of rapid growth, accumulation of fat is remarkably rapid during the first
6 months of age. In contrast, body water content, particularly the extracellular/
intracellular ratio, continues to decrease throughout infancy (Fomon and Nelson
2002). From the drug disposition point of view, it is notable that the weight of liver
and kidney relative to total body weight reaches maximum in the 1- to 2-year-old
child, at the period of life when capacity for drug metabolism and elimination also
tends to be greatest (Kauffman 2005; Murry et al. 1995)

and Typical Disorders with Their Health Problems
Respiratory Tract Infections
During the stage of intense lung growth and airway remodeling, small airway size
predisposes the child to acute obstructive lower airway diseases, e.g., bronchiolitis
(see also “Receptors/Binding Sites”), as well as to upper respiratory tract infections.
These infections probably lead to edema and dysfunction of the Eustachian tube,
which frequently contributes to middle ear infection (otitis media) (Kerschner 2007).
General Susceptibility to Infectious Diseases
Postnatal maturation of the immune system is not yet complete during early
childhood, similar to the respiratory system (Holt et al. 2005). The reduced capa-
bility to express a sustained immune response predisposes young children to
infectious diseases. In addition, this concurrent maturation of immunologic and
respiratory functions may have implications for programming of long-term response
patterns to exogenous inflammatory stimuli within the immune and respiratory
systems (Holt et al. 2005).
Seizures
As already mentioned in “Increased Susceptibility to Seizure” and “Neurotrans-

mitters, Transporters, and Channels”, this period of maturation is associated with
the highest tendency for seizure activity of anytime in life. A large number of
pathological processes may lead to seizures, including birth trauma and hypoxic–
ischemic insults immediately after birth, systemic infections and metabolic
imbalances in neonates, or fever in febrile seizures, which typically happen in
infants and young children (Ben-Ari and Holmes 2006). The high excitatory state
of the immature brain may also have some impact on the paradoxical effects of
midazolam in the very young (Tobin 2008).
Neoplastic Diseases
Embryonic tumors such as neuroblastoma, nephroblastoma (Wilms tumor), and

retinoblastoma are most common during the first year of life. These tumors are
much less common in older children and adults after cell differentiation processes
have slowed considerably (Kadan-Lottick 2007).
Frequently but not always, older infants, toddlers, and young children (see also
“Functional and Physiological Processes with Their Pathophysiology and Typical
Disorders and Their Health Problems”) exhibit the greatest overall drug clearance,
which is the result of the high metabolic and excretory function of liver and kidney.
For example, the half-life of diazepam is shortest in infants and longest in preterm
newborns and the elderly, with the magnitude of differences being more than
threefold (Coffey et al. 1983; Kauffman 2005; Mandelli et al. 1978). This “toddler
overshoot” may lead to therapeutic failure in cases where insufficient dose for age
is administered (Anderson and Lynn 2009; Chen et al. 2006; L€aer et al. 2005).
(For more clinically relevant examples, see “Major Organs of Metabolism and
Elimination”.)
3.3.4 Ontogeny of Drug Targets
Obstructive bronchiolitis responds poorly to b-adrenergic agonists (betamimetics)

due, at least in part, to reduced b-adrenergic receptor sites in the bronchial tree of
the wheezing toddler (Chavasse et al. 2002; Gadomski and Bhasale 2006; Lenney
and Milner 1978; Schindler 2002). Lack of betamimetic response may also be due
to small airways, mucus secretion, and to vasodilatation with mucosal edema of the
bronchial wall in bronchiolitis. Betamimetics probably have minimal effect on
airway edema as opposed to bronchial smooth muscle contraction. Thus, the most
likely explanation of this inconsistency or even failure of a bronchodilator response
is the heterogeneity of causes for infantile wheezing (Barr et al. 2000; Subbarao and
Ratjen 2006).
Mediators
More recently, another mediator system has been discussed that might be involved
in hyperresponsiveness of the tracheal–bronchial system of an infant or toddler. In a
well-established guinea pig maturational model that utilizes tracheal strips from
infant, juvenile, and adult animals, the role of airway smooth muscle in immature
airway hyperresponsiveness has been studied (Chitano et al. 2005). In contrast to
the adult, the infantile airway smooth muscle characteristically has a prostanoid-
mediated reduction of spontaneous relaxation during electric field stimulation
(Wang et al. 2008). Inhibition of prostanoid synthesis abolishes this reduced
relaxation and the age difference. A major role for leukotrienes was excluded.
Thus, it was concluded that the reduced spontaneous relaxation in immature airway
smooth muscle of the guinea pig and probably the airway hyperresponsiveness in
the young is associated with and most likely causally related to increased release of
contractile prostanoid (PGF2a, PGD2, and TXA2) (Wang et al. 2008). However,
extrapolation of the animal data to infants and toddlers with obstructive airway
disease has not yet been validated through well-designed efficacy and toxicity
studies with prostanoid synthesis inhibitors. Such well-controlled clinical studies
would be quite helpful in resolving the debate as whether ibuprofen is deleterious
or protective in children with asthma-related symptoms (Kanabar et al. 2007;
Kauffman and Lieh-Lai 2004).
Immune function
Another system, which is subjected to a variety of maturation processes, is the

complex in vivo immune system. This complexity makes it extremely difficult to
assess its activity quantitatively. Thus, an in vitro model with peripheral blood
monocytes has been established, which enables the quantification of cellular phar-
macodynamics of the immunosuppressant cyclosporine (Marshall and Kearns
1999). Two surrogate biomarkers of effect have been chosen: Cell proliferation
as a functional, yet nonspecific, marker of lymphocyte response to antigen and IL-2
expression as a specific marker of CD4 + lymphocyte activation. As reflected
by significant age dependence in the derived pharmacodynamic parameters of
IC50 (cell proliferation) and IC90 (IL-2 expression), the cellular targets for cyclo-
sporine action obtained from infants (<12 months of age) showed a twofold or
respectively a sevenfold higher sensitivity to cyclosporine as compared with chil-
dren, adolescents, and young adults (Marshall and Kearns 1999). This factor, if
neglected, may be a source of iatrogenic risk during immunosuppressive therapy of
an infant, e.g., after allograft transplantation.
Thermoregulation
In a PK/PD study with ibuprofen, a more favorable antipyretic response was

observed for infants compared with older children, despite a pharmacokinetic
profile whose parameter estimates were independent of age (Kauffman and Nelson
1992). A mechanism for this age-related difference in the antipyretic response is
postulated as follows: Relative surface area in infants is 1.7 times of that in children
(>6 years). The skin is the primary organ through which heat is emitted. So the
patient with the greatest body surface area relative to the body mass will be most
efficient at decreasing body temperature (Kauffman and Nelson 1992).
3.3.5 Environment and Critical Window of Development
Tobacco Exposure Contributes to Sudden Infant Death Syndrome
A critical window of vulnerability of the nicotinic acetylcholine receptors

(nAChRs) is hypothesized (Cnattingius 2004; Dwyer et al. 2009; Kinney 2009).
Sudden infant death syndrome (SIDS) remains the leading cause of postnatal
infant mortality. There is a major association between intrauterine exposure to
cigarette smoking and postnatal environmental tobacco smoke and the risk for
SIDS. Furthermore, this risk of death is positively correlated with daily cigarette
use (Hunt and Hauck 2007). In searching for an underlying biological mechanism
(s), the “brainstem hypothesis” was born (Kinney 2009), which appears to be quite
logical as the brainstem is the key brain region that controls the autonomic nervous
system including breathing, blood pressure, chemosensitivity, temperature, and
upper airway reflexes.
Although SIDS most likely results from a complex interaction of several dys-
functional neurotransmitter systems in the brainstem, there is good evidence from
the clinical literature and experimental animal models that the diverse effects
of nicotine exposure interfere with the critical regulatory role of nAChRs during
prenatal, early postnatal, and even adolescent brain maturation (Dwyer et al. 2009).
Various maturational processes in the brain are physiologically regulated by ace-
tylcholine (ACh) via activation of nAChRs, which are ligand-gated ion channels.
In accordance with the key regulatory role of ACh throughout ontogenesis, there
is a transient appearance and alteration in the subunit composition of nAChRs,
particularly during critical periods when brain maturation is most sensitive to
perturbation (Dwyer et al. 2009). This is consistent with the key regulatory role
of ACh of nAChR ontogenesis. Thus, it is not surprising that this transmitter system
can be perturbed by exogenous nicotine exposure during vulnerable developmental
windows, leading to serious and persisting consequences.
Methods to assess the function of the autonomic nervous system in infants of
mothers who smoked will be essential to investigating the longer term effects
of nicotine exposure. So far, during passive repositioning (60 head-up tilt)
nicotine-exposed infants exhibit persistent (up to 1 year) cardiovascular stress
hyperreactivity with orthostatic dysregulation (Cohen et al. 2010). It remains to be

explored, if this autonomic dysfunction in infants of smoking mothers leads to
longer lasting “reprogramming” of infant blood pressure control mechanisms and
eventually to hypertension. If this were found to be so, autonomic dysregulation in
the infant would potentially be an early predictive test for long-term suseptibility to
cardiovascular complications later in life.
3.4 The Child: Period of Language, Socialization,

and Continued Growth
This period is characterized by slower growth rate with slender figure, increasing
muscular mass, and relative stable body habitus until the pubertal growth spurt. In
general, the various composition compartments – except the extracellular water
compartment – remain basically unchanged during this period of steady growth
(Ellis 2000; Kauffman 2005).
3.4.2 Functional and Physiological Processes with Their Pathophysiology

and Typical Disorders and Their Health Problems
Four Diseases with Immune Dysfunction
– Rheumatic diseases of childhood, including connective tissue and collagen

diseases, are characterized by autoimmune activity of T- and B-lymphocytes.
Typical systemic but nonspecific manifestations are arthralgia, weakness,
and fever, which make it absolutely necessary to exclude infections and
malignancies (Miller 2007).
– Acute glomerulonephrits, such as poststreptococcal glomerulonephritis, is
mediated by nephritogenic immune complexes and activation of the comple-
ment system. It is most common in children aged 5–12 years and uncommon
before the age of 3 years (Davis and Avner 2007).
– Childhood asthma represents the most common allergic disorder in children,
with severe immune dysregulation and marked expansion of T helper type
2 (Th2) cells that secrete cytokines favoring IgE synthesis and eosinophilia
(Leung 2007). Approximately 80% of all asthmatics report disease onset prior
to 6 years of age (Liu et al. 2007).
– Diabetes mellitus type 1 is the most common endocrine–metabolic disorder of
childhood and adolescence with two peaks of presentation occurring at the age
of 5–7 years and at the time of puberty. The first peak may correspond to the time
of increased exposure to infectious agents coincident with the beginning of
school (Alemzadeh and Wyatt 2007). The pathogenesis of this disorder is con-
sidered to be an autoimmune destruction of pancreatic islet b-cells, which
eventually leads to insulin deficiency.
Epilepsy
Childhood absence epilepsy is the most common form of pediatric seizures. This
benign idiopathic generalized epilepsy in an otherwise apparently healthy child is
characterized by daily frequent but brief spells. It is uncommon before the age of
5 years and typically goes into remission at the age of 10–12 years with a generally
good prognosis (Guerrini 2006).
Neoplastic Diseases
The most common lymphohematopoietic neoplastic diseases, i.e., acute lympho-

blastic leukemia and lymphomas, have a striking peak incidence between 2 and
6 years of age. In addition to this age relationship, genetic and environmental risk
factors have been observed such as Down syndrome and ionizing radiation (Kadan-
Lottick 2007; Tubergen and Bleyer 2007). It is of note that pediatric neoplastic
diseases differ markedly from adult malignancies (predominately solid cancers) in
prognosis, distribution, tumor site, and molecular biology.
Neurobehavioral Disorders
This period is characterized by increased intellectual performance, rapid language

acquisition, socialization, and appearance of behavior disorders. The most common
neurobehavioral disorder of childhood and one of the most prevalent chronic health
conditions affecting school-aged children are the attention-deficit/hyperactivity
disorders (ADHD). Multiple factors have been implicated in the etiology of
ADHD, such as perinatal complications (e.g., toxemia and traumatic delivery),
maternal smoking and alcohol use, and genetic disposition (Raishevich and Jensen
2007). Unfortunately, a childhood diagnosis of ADHD often leads to persistent
ADHD throughout the life span. Besides psychosocial and behaviorally oriented
treatment, psychostimulant medication is a therapeutic option. However, this last
option is not without risk, particularly when carried out over an extended period of
time (see “Ontogeny of Drug Targets”).
Accidents
Intensified physical activity, practice of skills, and participation in competitive

sports lead to increased risk of vehicular accidents and sports-related injuries at
schools or playground, particularly among middle-school-aged children (6–11years

of age). Upper extremity and head injuries are by far most common.
The child at this stage of development is intermediate between the immature infant
and the young adult (Kauffman 2005). The clearances of many hepatically
metabolized medicines, such as theophylline (Hendeles and Weinberger 1983),
omeprazole (Litalien et al. 2005), midazolam (Reed et al. 2001), and isoniazid
(McIlleron et al. 2009) are increased in children (ages 2–11 years) compared with
those of adults. This also applies to medicines, which are predominantly eliminated
by the kidney, such as sotalol (L€aer et al. 2005) and amikacin (Vogelstein et al.
1977). Consequently, higher doses are often required to achieve comparable thera-
peutic levels.
Glucose Metabolism
Recently, Hussain and coworkers reported hypoglycemia in children secondary to

b-blocker treatment (Hussain et al. 2009). They presented five patients (1–5 years)
out of 570 patients at their institution who were prescribed regular b-blockers over
the same time period, who had severe hypoglycemic episodes while taking
noncardioselective b-blockers (nadolol and propranolol) for prevention of arrhyth-
mia. From these data, they estimated an overall risk of hypoglycemia to be around
1%. However, when only those children younger than six years of age were
considered, they speculated that the hypoglycemic risk is threefold higher. Thus,
at that age young children, who are per se prone to idiopathic ketotic hypoglycemia,
have to be monitored very carefully when treated with b-blockers, which decreases
glycogenolysis, gluconeogenesis, and lipolysis. At least two major possibilities for
this instability of glucose homeostasis have to be considered: (1) maturational
dysregulation in the adrenergic system, including particularly signal transduction
via the b2-adrenergic receptors; or (2) some intrinsic hepatic weakness of glucose
mobilization combined with some inappropriate feeding regimen during this
phase of early childhood. Ongoing studies with propranolol for severe infantile
hemangiomas may provide some additional data in a younger age group (Sans et al.
2009), which will be helpful to answer these questions.
Coagulation System
The age-dependent coagulation system can be described as an evolving and yet

functional system in the young (Kuhle et al. 2003). For optimal prevention and
diagnosis of hemostatic problems, reference ranges for children of all age groups
have been established. However, information on the developmental and matura-
tional changes in the pharmacodynamics of anticoagulants such as warfarin is very
limited. Apparently, Japanese children (1–11 years) with low plasma concen-
trations of vitamin K-dependent coagulation factors possess increased sensitivity
to the anticoagulant effect of warfarin (Takahashi et al. 2000). Although prepuber-
tal and adult patients showed comparable mean plasma concentrations of warfarin,
prepubertal children showed significant lower plasma concentrations of protein C
and prothrombin fragments 1 and 2 and higher INR. This augmented response to
warfarin in children, e.g., with congenital heart disease and valve replacement,
should be considered when estimating the most appropriate warfarin dose for them.
3.4.5 Environment and Critical Windows of Development
In this prepubescent pediatric population, one has primarily to consider the long-
term consequences of drug treatment of patients with chronic diseases or conditions
known as the “new pediatric morbidity” such as childhood asthma, neurodeve-
lopmental disorders, and cancer as well as obesity, arterial hypertension, and type
2 diabetes (Cox et al. 2008; Hausner et al. 2008). The latter disorders are the
consequences of “modern lifestyle” in Western as well as in emerging countries,
characterized by a decline in physical activity and an increased consumption of
“fast” processed food with high salt and caloric content. Consequently, there is a
growing need for antihypertensives, antihyperlipidemics, and type 2 antidiabetic
drugs in children (Cox et al. 2008). The long-term consequences over the whole life
span are as yet unknown.
Chemotherapy
While cancer as a cause of morbity and mortality is not new to the pediatric
population, as the survival rate has dramatically improved for a variety of neoplas-
tic diseases over the past several decades, the prevalence and duration of chemo-
therapy has increased. This success in cancer survival is not without long-term
effects on later maturation processes, such as those of the reproductive, immuno-
logical, skeletal, neural, behavioral, and cardiovascular systems. For example, the
anthracycline doxorubicin, a very effective chemotherapeutic agent for certain
childhood malignancies, is associated with a delayed serious and potentially
life-threatening cardiotoxicity. Even years after completion of medication, parti-
cularly when treatment occurred during infancy and early childhood, persistent
myocardiocyte loss, myocardial fibrosis, and failure of myocardial growth are
observed as sequelae of former doxorubicin treatment (Hausner et al. 2008). In a
more recent study, it has been shown that the relative hazard of congestive heart
failure, pericardial disease, and valvular abnormities in adult survivors of childhood
and adolescent cancer treated with anthracyclines increased two to five times
(Mulrooney et al. 2009).
Asthma-Controller Medication
The most common chronic medical condition of children is asthma. Accordingly,

use of asthma-controller medication is the highest of all chronic medication use
in children (Cox et al. 2008; Hausner et al. 2008). Unfortunately, the potentially
negative effects of inhaled glucocorticoids on linear growth, even in the absence of
hypothalamic–pituitary axis suppression, as well as long-term deleterious effects on
the cardiovascular and pulmonary systems from early intervention with long-acting
b-adrenergic receptor agonists are not sufficiently well studied Ducharme et al.
2010; Hausner et al. 2008).
ADHD Medication
In the treatment of ADHD, pharmacotherapy with psychostimulants is commonly

employed in school-aged boys (less commonly in girls) to increase the ability to
concentrate, improve overall school performance, and attenuate disturbing hyper-
activity. With the marked increase in the prescription of these medicines, such as
methylphenidate and amphetamines, the warnings about questionable cardiovascu-
lar safety of these compounds have become more and more insistent (Nissen 2006).
All these sympathomimetic psychostimulants substantially increase heart rate and
blood pressure, potentially predisposing the child to serious cardiovascular effects
or sudden death, particularly in subgroups of individuals at heightened risk, such as
those with congenital heart disorders and/or increased blood pressure. In addition,
these agents may have negative effects on sleep, appetite, and growth; effects
that are certainly not irrelevant during childhood and adolescence. Thus, it is of
utmost importance to carefully consider the benefit-to-risk when prescribing
psychostimulant medications.
3.5 The Adolescent: Period of Final Growth and Reproductive

Maturation
Puberty is another extremely important phase in the physical and psychosocial

development of the adolescent. The age of onset of puberty varies as a function of
ethnicity, health status, genetics, nutrition, and activity level. Generally, puberty
begins between 8 and 14 years and occurs almost two years earlier in females than
males (Tanner and Davies 1985).
The main features of this maturation period are as follows: Pubertal growth
spurt, which accounts for approximately 25% of final adult height, changes in the
body habitus, and remodeling of the body over a relative short period of time with
sexual maturation. This includes feminization with more fat content in females and
masculinization with more muscular mass in males (Ellis 2000). Besides these
changes in skeletal growth and alteration in body composition, cardiorespiratory
changes take place such as doubling of the weight of the heart and rise in systolic
blood pressure primarily in boys associated with increase in lung size and vital
capacity and a drop in respiratory rate (Irwin 2003). Blood volume, red cell mass,
and hematocrit increase throughout puberty in boys, while these parameters remain
constant for girls. At the same time, dramatically increased levels of gonadal steroid
hormones, which are secreted in a pulsatile manner, are involved in regulating
plastic changes in neuronal structure and function. These modulation processes of
brain circuits at puberty can have effects on changes in social behavior, risk-taking
behaviors, and cognitive function at adolescence (Cameron 2004; Paus et al. 2008).
Thus, it is not so surprising, when these processes are suboptimal in timing and/or
magnitude that the risk of cognitive, affective, and addictive disorders increases
(see below).
3.5.2 Functional and Physiological Processes and Their Pathophysiology

and Typical Disorders and Their Health Problems
Growth Retardation
Growth retardation, also called stunting, may be a consequence of a variety of

factors such as undernutrition, intestinal worm infections, vitamin D deficiency
(rickets), chronic intoxication with arsenic and manganese (e.g., through household
wells in South Asia), chronic and/or consumptive diseases, long-term drug-induced
immunosuppression (e.g., posttransplantation), and premature pubertal develop-
ment (precocious puberty). In general, optimal intrauterine, infant, and childhood
growth is an important basis for satisfactory growth during adolescence.
Endocrine Dysfunctions
– Precocious, markedly delayed, or absent puberty are disorders of the hypothala-

mic–pituitary–gonadal (HPG) axis. Hormonal interventions are directed at both
the acute and the long-term consequences of disturbed pubertal development,
e.g., treatment of a patient with gonatropin-dependent early puberty (true preco-
cious puberty) with gonadotropin-releasing hormone (GnRH) analogues to post-
pone pubertal maturation and to secure the pubertal growth spurt and final height
by preventing premature closure of the long bone growth plates (Br€amswig and
D€ubbers 2009). In contrast, delayed pubertal development may be induced by

substitution with gonadal steroid hormones in a teenager with absent puberty as
a result of a gonadal disorder with hypergonatropic hypogonadism as seen in
chromosomal anomalies, such as Ulrich–Turner syndrome.
– Primary dysfunctional uterine bleeding and dysmenorrhea remain leading
reproductive complaints in menstruating female adolescents. This results from
the immature HPG axis and painful prostaglandin-stimulated myometrial con-
traction, respectively. Thus, early longer term treatment with oral contraceptives
and/or prostaglandin synthesis inhibitors appears to be justified (Moscicki 2003),
although long-term consequences of this therapy on the reproductive system
have not yet been studied.
– After the first peak of presentation in the early school age (see “Four Diseases
with Immune Dysfunction”), diabetes mellitus type 1 has the second peak of
disease onset. This is thought to be related to the pubertal growth spurt induced
by gonadal steroids and growth hormone secretion, which antagonizes insulin
(Alemzadeh and Wyatt 2007). In this context, it is of note that the second peak in
onset occurs – as one would have expected – earlier in girls than in boys.
Malignancies
Malignancies, which are common in early adulthood, such as testicular and ovarian
carcinoma, Hodgkin disease, the sarcomas such as osteosarcoma, Ewing sarcoma,
and other soft-tissue sarcomas are the most common types of cancer in adolescence
(Kadan-Lottick 2007).
Emotional Instability
It is believed that gonadal steroid hormones modulate the activity of a number

of neurotransmitter systems, including cholinergic, serotonergic, noradrenergic,
and dopaminergic neurons. These complex central nervous system pathways play
central roles in regulating many higher order brain functions, including cognitive
functions and emotional regulation (Cameron 2004). It is therefore not surprising
that suicides, drug addiction, and risk-taking behavior are major health problems in
adolescents.
– Substance use and abuse such as binge drinking and marijuana and cocaine
use are quite common in the adolescent population particularly in the Western
countries. Both cigarette use and alcohol use begin early in adolescence with a
mean age of onset of about 12 years. Girls consistently report greater daily use
of cigarettes than boys, whereas boys report greater use of alcohol than girls
(Marcell and Irwin 2003a). Continued nicotine abuse in the female population
into the childbearing years has grave implications for future pregnancies,
including increased risk of fetal growth restriction, preterm births, still-

births, placental abruption, and possibly also sudden infant death syndrome
(Cnattingius 2004).
– Unintentional injuries, as the result of a high risk-taking behavior in combina-
tion with alcohol consumption, are the primary cause of premature mortality in
adolescents, accounting for more than 50% of deaths in that age group. It is not
surprising that the mortality rate in male teenagers is nearly twice that of girls.
Acute traumatic injuries resulting from nonfatal accidents account for the largest
number of hospital days and outpatient physician visits for both adolescent boys
and girls (Marcell and Irwin 2003b).
Sexual Behavior
Adolescents continue to initiate sexual activity early in the second decade of life.
Again age of menarche, ethnic origin, and social status may have a significant
influence on the age of first sexual intercourse; but one can assume that more than
50% of middle teen adolescents will have this experience and are prone to sexually
transmitted diseases and ectopic pregnancies (Marcell and Irwin 2003c; Dalton
2007).
– Covariation of risk behaviors
As already mentioned above, there is a close association of alcohol and uninten-
tional injury. There also appears to be a relationship between cigarette smoking
and the use of illicit substances as well as failure to use effective contraception
leading to unintended pregnancy (Marcell and Irwin 2003d). In the worst case,
the sequence of progression can be as follows: alcohol and cigarettes precede
marijuana use, which is followed by other illicit drugs (including psychedelics,
cocaine, heroin, and prescribed and nonprescribed stimulants, sedatives, and
tranquilizers), leading to a cumulative effect of all substances and sometimes to
high-risk teenage pregnancies.
Mental Health Problems During Adolescence
– Depression and suicide

Transient depressive feelings are common during adolescence. Among these
patients, the risk of suicide is increased significantly. Presently, it is the third
leading cause of death in adolescents (Boris and Dalton 2007). Rates of com-
pleted suicide increase steadily across the teen years, peaking in the early 20s.
The male:female ratio for completed suicide is approximately 4:1. For every
completed suicide, it is estimated that there are many more (about 50) suicide
attempts with significant underreporting and female predominance. Most female
suicide attempts involve drug ingestions or superficial cutting, whereas males
use more lethal means such as firearms and hanging (Boris and Dalton 2007).
Although adolescent females are more at risk for depression compared to males,
males are generally more aggressive and impulsive than females.
– Eating disorders
Anorexia nervosa (AN) and bulimia nervosa (BN) are common psychiatric
disorders in adolescents and young adults with high rates of morbidity and mor-
tality. The incidence of both disorders has increased in the general population
over the last two decades and remains eight times higher in the female than male
teenage population (Abraham and Stafford 2007).
Extreme feelings of dissatisfaction with weight and shape and fear of gaining
weight are the main causes of these disorders, leading typically to amenorrhea
and to a maintenance weight of 15% below the ideal body weight in AN. Other
clinical manifestations of eating disorders include severe malnutrition, self-
induced vomiting (particularly in BN with episodes of compulsive overeating),
and use of laxatives and/or diuretics. This may lead to dehydration, peripheral
vasoconstriction, hypothermia, bradycardia, severe electrolyte imbalance with
cardiac arrhythmia, osteopenia with stress fractures, hypoproteinemia with
peripheral edema, and decreased glomerular filtration. This complex clinical
condition is associated with severe medical and psychiatric comorbidity for
which pharmacotherapy has a limited role at the present time. Nevertheless,
the drugs mainly used in the treatment of eating disorders are antidepressants
such as SSRIs, tricyclics, and atypical antipsychotic agents (Powers and Bruty
2009). However, dosing, side-effect profile, and long-term effects of these
medications in children and adolescents are not well studied (Hausner et al.
2008).
Around the onset of puberty with increased growth hormone levels and activation
of the reproductive axis, drug-metabolizing enzyme capacity begins gradually
to decline. This decline continues throughout adolescence and concludes with
attainment of adult capacity at the completion of pubertal development (Kennedy
2008). During this period of marked hormonal changes and fluctuation, an apparent
inverse relationship between levels of growth and sex hormones and drug-
metabolizing activity can be observed. For example, a Tanner stage-dependent
decrease in CYP1A2-mediated caffeine clearance has been described in healthy
adolescents (Lambert et al. 1986). A more direct demonstration of this relationship
was observed among growth hormone-deficient prepubertal children in whom
physiological growth hormone replacement was associated with a twofold increase
in the half-life of amobarbital, a probe of hepatic microsomal drug metabolism
(Redmond et al. 1978). At least in part, changes in body composition may also have
an effect on the V(d) as illustrated by a highly significant positive correlation of
Tanner stage with theophylline elimination half-life and lean body mass and
between lean body mass and V(d) in adolescents with asthma (Cary et al. 1991).
Gender differences in drug disposition also become more apparent during puberty
(Beierle et al. 1999; Kennedy 2008; Lambert et al. 1986).
Thus, the effects of rapid growth, sexual maturation, and the large amount of
variability in the timing of these developmental events on pharmacokinetics must
be considered during studies with teenagers. The concept of developmental rather
than chronological age should be applied whenever it is possible (Cary et al. 1991;
Finkelstein 1994; Kennedy 2008).
These ontogenetic and pharmacokinetic changes during this stage of growth and
sexual maturation are especially important when treating common chronic illnesses
of adolescence, such as asthma, diabetes, epilepsy, and depression. This complex
hormonal and pharmacotherapeutic interplay can further be complicated by on and
off oral contraceptive therapy, teenage pregnancy, smoking, self-medication, and
illicit drug use.
With respect to renal elimination, it is of note that glomerular filtration and
tubular absorption are not influenced by sexual maturation, in contrast to tubular
secretion of medicines, e.g., tubular secretion of digoxin, which declines during
adolescence to the level seen in adults (Linday et al. 1984; Linday et al. 1981).
Methotrexate, which is excreted by the kidney via glomerular filtration and tubular
secretion, also shows reduced clearance as a function of age through adolescence
(Donelli et al. 1995).
The effects of physical growth and sexual maturation on the expression of impor-
tant drug targets, such as receptors, transporters, and channels, remain essentially
unexplored. This is in contrast to the available comprehensive knowledge about
ontogenetic differences in pharmacodynamics in the perinatal period. A major
obstacle (hurdle) may be greater difficulties in monitoring quantitatively the rele-
vant clinical end points or appropriate surrogate markers of drug action, efficacy,
and toxicity throughout the course of pubertal development and sexual maturation.
Moreover, pediatricians have relatively neglected research in the area of adolescent
medicine in the past.
3.5.5 Environment and Critical Windows of Development
Long-term safety of medicines and, even more so, the long-term consequences
of addictive substances use and drug abuse are of major concern in this pediatric
population, e.g., tobacco and alcohol consumption and doping with central
stimulants or androgens (Dwyer et al. 2009; Hausner et al. 2008; Sj€oqvist et al.
2008).
Nicotine as a Gateway Drug
There is ample experimental and some epidemiological evidence that tobacco

or nicotine administration particularly during adolescence is a gateway drug that
increases the likelihood of subsequent use of other addictive substances (Dwyer
et al. 2009). The ability of nicotine to interfere via the AChRs directly or indirectly
with various transmitter systems such as the acetycholinergic, dopaminergic, or
serotonergic systems may play a role in subsequent addictive behavior. Although
the functional role of nAChRs in adolescent maturational processes has not been
fully explored, neurochemical and behavioral studies with experimental animals
suggest that they may regulate limbic system circuitry that is undergoing critical
experience-dependent reshaping during this period (Dwyer et al. 2009). Thus,
adolescence may be a particularly vulnerable period, during which nicotine expo-
sure might produce long-term changes in function of the limbic system. This system
supports a variety of functions including emotion, behavior, and long-term memory
and is hereby involved in addictive disorders.
Anabolic Androgenic Steroids
The misuse of performance-enhancing drugs such as anabolic androgenic steroids

is another example of the potential for long-term effects when used during this
vulnerable period of maturation. Unfortunately, use of performance enhancers is
quite common in young sportspeople, both in high schools and in noncompeting
amateurs with a high predominance of male students. The estimated percentage
in this adolescent population is at least 3–5% (Sj€oqvist et al. 2008). In early
adolescents (age 10–13 years), a typical adverse effect with permanent long-term
consequences from this kind of doping is premature closure of epiphysial growth
plates with ultimate stunted linear growth. In middle and late adolescence testicular
atrophy and gynecomastia in males and virilization and long-term amenorrhea in
females dominate the endocrine effects. The major cardiovascular side effects are
hypertrophic cardiomyopathy and hypertension. In addition, common neuropsy-
chiatric side effects include mood changes, such as mania, hypermania, depression,
and increased aggressive behavior (Sj€ oqvist et al. 2008). In combination with
alcohol and central stimulants, anabolic androgenic steroids seem to be strongly
synergistic in producing impulsive violent behavior or suicide and homicide,
respectively. The whole spectrum of the long-lasting effects of these steroids in
humans is not well studied, but at least the effects on muscular fibers last much
longer than a couple of years.
Psychostimulants
The long-term risk of extended use and misuse of central stimulants as perfor-
mance-enhancing drugs has already been mentioned and briefly discussed in
“ADHD Medication”. These risks are particularly relevant for the male teenage
population at secondary school, in which the diagnosis of ADHD is frequently
made with a prevalence of about 8% as compared to only 2% in girls (Huss et al.
2008).
4 Future Directions
There is a permanent need to fill the gaps of our knowledge about the continuous
developmental changes of therapeutic targets (e.g., enzymes, transporters,
receptors, and channels) from the fetus to young adult. These gaps include follow-
ing sections.
4.1 Appropriate Tools for Assessment of Drug Action
Development of age-appropriate methods and tools for the assessment of drug

actions and effects in the pediatric population, such as intermediate end point or
surrogate markers, biomarkers, functional tests, scores, scales, and PK/PD analyses.
4.2 Appropriate Animals and Cell Models
Development of appropriate and predictive animal models, cell systems, in vitro

tests, and in silico simulation; all tools which are important and helpful to manage –
at least in part – the delicate and ethically and legally complex situation of research
in a very vulnerable population.
4.3 Appropriate Methods for Long-Term Safety Effects
Development of appropriate epidemiological methods for the evaluation of long-

term safety and potential programming effects of pharmacological interventions at
an early stage of development, assessment of predictive value of surrogate end
points in predicting long-term efficacy and toxicity (particularly with chronic
exposures), identification of vulnerable windows of developmentally immature
organ systems (e.g., cardiovascular, neurological, immunological, and reproductive
systems) that might be especially sensitive to pharmacological perturbation, and
additional study to evaluate the impact of a disease state that is unique to children.
References
Abraham A, Stafford B (2007) Eating disorders. In: Kliegman RM, Behrman RE, Jenson HB,
Stanton BF (eds) Nelson textbook of pediatrics, 18th edn. Saunders Elsevier, Philadelphia
Ahlfors CE (2004) Effect of ibuprofen on bilirubin–albumin binding. J Pediatr 144:386–388
Ahmad I, Nemet D, Eliakim A, Koeppel R, Grochow D, Coussens M, Gallitto S, Rich J, Pontello
A, Leu SY, Cooper DM, Waffarn F (2010) Body composition and its components in preterm
and term newborns: a cross-sectional, multimodal investigation. Am J Hum Biol 22:69–75
al-Alaiyan S, al-Rawithi S, Raines D, Yusuf A, Legayada E, Shoukri MM, el-Yazigi A (2001)
Caffeine metabolism in premature infants. J Clin Pharmacol 41:620–627
Alcorn J, McNamara PJ (2002) Ontogeny of hepatic and renal systemic clearance pathways in
infants: part II. Clin Pharmacokinet 41:1077–1094
Alemzadeh R, Wyatt DT (2007) Diabets mellitus in children. In: Kliegman RM, Behrman RE,
Jenson HB, Stanton BF (eds) Nelson textbook of pediatrics, 18th edn. Saunders Elsevier,
Philadelphia
Allegaert K, van den Anker JN, Naulaers G, de Hoon J (2007) Determinants of drug metabolism in
early neonatal life. Curr Clin Pharmacol 2:23–29
Anderson GD, Lynn AM (2009) Optimizing pediatric dosing: a developmental pharmacologic
approach. Pharmacotherapy 29:680–690
Asmar BI, Abdel-Haq NM (2005) Macrolides, chloramphenicol, and tetracyclines. In: Yaffe SJ,
Aranda JV (eds) Neonatal and pediatric pharmacology – therapeutic principles in practice, 3rd
edn. Lippincott Williams & Wilkins, Philadelphia
Axelsson I, Jakobsson I, Lindberg T, Polberger S, Benediktsson B, Raiha N (1989) Macromolec-
ular absorption in preterm and term infants. Acta Paediatr Scand 78:532–537
Balazy M, Chemtob S (2008) Trans-arachidonic acids: new mediators of nitro-oxidative stress.
Pharmacol Ther 119:275–290
Barr FE, Patel NR, Newth CJ (2000) The pharmacologic mechanism by which inhaled epinephrine
reduces airway obstruction in respiratory syncytial virus-associated bronchiolitis. J Pediatr
136:699–700
Barrett DA, Rutter N (1994) Transdermal delivery and the premature neonate. Crit Rev Ther Drug
Carrier Syst 11:1–30
Bartelink IH, Rademaker CM, Schobben AF, van den Anker JN (2006) Guidelines on paediatric
dosing on the basis of developmental physiology and pharmacokinetic considerations. Clin
Pharmacokinet 45:1077–1097
Battino D, Estienne M, Avanzini G (1995) Clinical pharmacokinetics of antiepileptic drugs in
paediatric patients. Part I: phenobarbital, primidone, valproic acid, ethosuximide and
mesuximide. Clin Pharmacokinet 29:257–286
Beierle I, Meibohm B, Derendorf H (1999) Gender differences in pharmacokinetics and pharma-
codynamics. Int J Clin Pharmacol Ther 37:529–547
Ben-Ari Y, Holmes GL (2006) Effects of seizures on developmental processes in the immature
brain. Lancet Neurol 5:1055–1063
Ben-Ari Y, Gaiarsa JL, Tyzio R, Khazipov R (2007) GABA: a pioneer transmitter that excites
immature neurons and generates primitive oscillations. Physiol Rev 87:1215–1284
Berlin CM Jr (2005) The excretion of drugs and chemicals in human milk. In: Yaffe SJ, Aranda JV
(eds) Neonatal and pediatric pharmacology – therapeutic principles in practice, 3rd edn.
Lippincott Williams & Wilkins, Philadelpha
Berlin CM Jr, Paul IM, Vesell ES (2009) Safety issues of maternal drug therapy during
breastfeeding. Clin Pharmacol Ther 85:20–22
Bhat AM, Meny RG (1984) Alimentary absorption of gentamicin in preterm infants. Clin Pediatr
(Phila) 23:683–685
Bittigau P, Sifringer M, Ikonomidou C (2003) Antiepileptic drugs and apoptosis in the developing
brain. Ann NY Acad Sci 993:103–114
Boie Y, Rushmore TH, rmon-Goodwin A, Grygorczyk R, Slipetz DM, Metters KM, Abramovitz
M (1994) Cloning and expression of a cDNA for the human prostanoid IP receptor. J Biol
Chem 269:12173–12178
Boréus LO (1972) Fetal pharmacology. Raven Press, New York
Boris NW, Dalton R (2007) Suicide and attempted suicide. In: Kliegman RM, Behrman RE,
Philadelphia
Bory C, Baltassat P, Porthault M, Bethenod M, Frederich A, Aranda JV (1979) Metabolism of
theophylline to caffeine in premature newborn infants. J Pediatr 94:988–993
Bouayad A, Kajino H, Waleh N, Fouron JC, Andelfinger G, Varma DR, Skoll A, Vazquez A,
Gobeil F Jr, Clyman RI, Chemtob S (2001) Characterization of PGE2 receptors in fetal and
newborn lamb ductus arteriosus. Am J Physiol Heart Circ Physiol 280:H2342–H2349
Bouwmeester NJ, van den Anker JN, Hop WC, Anand KJ, Tibboel D (2003) Age- and therapy-
related effects on morphine requirements and plasma concentrations of morphine and its
metabolites in postoperative infants. Br J Anaesth 90:642–652
Br€amswig J, D€ubbers A (2009) Disorders of pubertal development. Dtsch Arztebl Int 106:295–303
Cameron JL (2004) Interrelationships between hormones, behavior, and affect during adolescence:
understanding hormonal, physical, and brain changes occurring in association with pubertal
activation of the reproductive axis. Introduction to part III. Ann N Y Acad Sci 1021:110–123
Cary J, Hein K, Dell R (1991) Theophylline disposition in adolescents with asthma. Ther Drug
Monit 13:309–313
Celsi G, Aperia A (1993) Sodium, chloride, and water. In: Holliday MA, Barratt TM, Evner ED
(eds) Pediatric nephrology. Lippincott Williams & Wilkins, Philadelphia
Charles BG, Townsend SR, Steer PA, Flenady VJ, Gray PH, Shearman A (2008) Caffeine citrate
treatment for extremely premature infants with apnea: population pharmacokinetics, absolute
bioavailability, and implications for therapeutic drug monitoring. Ther Drug Monit
30:709–716
Chavasse R, Seddon P, Bara A, McKean M (2002) Short acting beta agonists for recurrent wheeze
in children under 2 years of age. Cochrane Database Syst Rev: CD002873
Chen N, Aleksa K, Woodland C, Rieder M, Koren G (2006) Ontogeny of drug elimination by the
human kidney. Pediatr Nephrol 21:160–168
Chitano P, Wang L, Murphy TM (2005) Mechanisms of airway smooth muscle relaxation during
maturation. Can J Physiol Pharmacol 83:833–840
Clapp DW (2006) Developmental regulation of the immune system. Semin Perinatol 30:69–72
Clyman RI, Waleh N, Kajino H, Roman C, Mauray F (2007) Calcium-dependent and calcium-
sensitizing pathways in the mature and immature ductus arteriosus. Am J Physiol Regul Integr
Comp Physiol 293:R1650–R1656
Cnattingius S (2004) The epidemiology of smoking during pregnancy: smoking prevalence,
maternal characteristics, and pregnancy outcomes. Nicotine Tob Res 6(Suppl 2):S125–S140
Coffey B, Shader RI, Greenblatt DJ (1983) Pharmacokinetics of benzodiazepines and
psychostimulants in children. J Clin Psychopharmacol 3:217–225
Coffman BL, Rios GR, King CD, Tephly TR (1997) Human UGT2B7 catalyzes morphine
glucuronidation. Drug Metab Dispos 25:1–4
Cohen G, Jeffery H, Lagercrantz H, Katz-Salamon M (2010) Long-term reprogramming of
cardiovascular function in infants of active smokers. Hypertension 55:722–728
Colussi G, Bettinelli A, Tedeschi S, De Ferrari ME, Syren ML, Borsa N, Mattiello C, Casari G,
Bianchetti MG (2007) A thiazide test for the diagnosis of renal tubular hypokalemic disorders.
Clin J Am Soc Nephrol 2:454–460
Commare CE, Tappenden KA (2007) Development of the infant intestine: implications for
nutrition support. Nutr Clin Pract 22:159–173
Cox ER, Halloran DR, Homan SM, Welliver S, Mager DE (2008) Trends in the prevalence of
chronic medication use in children: 2002–2005. Pediatrics 122:e1053–e1061
Dalton R (2007) The development of sexual behavior. In: Kliegman RM, Behrman RE, Jenson
HB, Stanton BF (eds) Nelson textbook of pediatrics, 18th edn. Saunders Elsevier, Philadelphia
Davis ID, Avner ED (2007) Acute poststreptococcal glomerulonephritis. In: Kliegman RM,
Behrman RE, Jenson HB, Stanton BF (eds) Nelson textbook of pediatrics, 18th edn. Saunders
Elsevier, Philadelphia
de Wildt SN, Kearns GL, Hop WC, Murry DJ, Bdel-Rahman SM, van den Anker JN (2002)
Pharmacokinetics and metabolism of oral midazolam in preterm infants. Br J Clin Pharmacol
53:390–392
Donelli MG, Zucchetti M, Robatto A, Perlangeli V, D’Incalci M, Masera G, Rossi MR (1995)
Pharmacokinetics of HD-MTX in infants, children, and adolescents with non-B acute lympho-
blastic leukemia. Med Pediatr Oncol 24:154–159
Doyle LW, Ehrenkranz RA, Halliday HL (2010) Dexamethasone treatment in the first week of life
for preventing bronchopulmonary dysplasia in preterm infants: a systematic review. Neonatol-
ogy 98:217–224
Dubois J, Dehaene-Lambertz G, Perrin M, Mangin JF, Cointepas Y, Duchesnay E, Le BD, Hertz-
Pannier L (2008) Asynchrony of the early maturation of white matter bundles in healthy
infants: quantitative landmarks revealed noninvasively by diffusion tensor imaging. Hum
Brain Mapp 29:14–27
Ducharme FM, Ni CM, Greenstone I, Lasserson TJ (2010) Addition of long-acting beta2-agonists
to inhaled steroids versus higher dose inhaled steroids in adults and children with persistent
asthma. Cochrane Database Syst Rev 4: CD005533
Dwyer JB, McQuown SC, Leslie FM (2009) The dynamic effects of nicotine on the developing
brain. Pharmacol Ther 122:125–139
Ellis KJ (2000) Human body composition: in vivo methods. Physiol Rev 80:649–680
Evans N, Moorcraft J (1992) Effect of patency of the ductus arteriosus on blood pressure in very
preterm infants. Arch Dis Child 67:1169–1173
Fawer CL, Torrado A, Guignard JP (1979) Maturation of renal function in full-term and premature
neonates. Helv Paediatr Acta 34:11–21
Fettermann GH, Shuplock NA, Philipp FJ, Gregg HS (1965) The growth and maturation of human
glomeruli and proximal convolutions from term to adulthood: studies by microdissection.
Pediatrics 35:601–619
Finkelstein JW (1994) The effect of developmental changes in adolescence on drug disposition.
J Adolesc Health 15:612–618
Fischl R (1902) Ueber Behandlung und Medikation bei Kindern im Allgemeinen. In: Biedert PH
(ed) Lehrbuch der Kinderkrankheiten. Verlag von Ferdinand Enke, Stuttgart
FitzGerald GA, Patrono C (2001) The coxibs, selective inhibitors of cyclooxygenase-2. N Engl
J Med 345:433–442
Fitzgerald M, Walker SM (2009) Infant pain management: a developmental neurobiological
approach. Nat Clin Pract Neurol 5:35–50
Fleck C, Br€aunlich H (1995) Renal handling of drugs and amino acids after impairment of kidney
or liver function – influences of maturity and protective treatment. Pharmacol Ther 67:53–77
Fomon SJ, Nelson SE (2002) Body composition of the male and female reference infants. Annu
Rev Nutr 22:1–17
Food and Drug Administration (2000) International Conference on Harmonisation; guidance on
E11 clinical investigation of medicinal products in the pediatric population; availability.
Notice. Fed Regist 65:78493–78494
Fraser J, Nadeau J, Robertson D, Wood AJ (1981) Regulation of human leukocyte beta receptors
by endogenous catecholamines: relationship of leukocyte beta receptor density to the cardiac
sensitivity to isoproterenol. J Clin Invest 67:1777–1784
Freye E (1996) Development of sensory information processing – the ontogenesis of opioid
binding sites in nociceptive afferents and their significance in the clinical setting. Acta
Anaesthesiol Scand Suppl 109:98–101
Fr€
olich JC (1997) A classification of NSAIDs according to the relative inhibition of cyclooxygen-
ase isoenzymes. Trends Pharmacol Sci 18:30–34
Gadomski AM, Bhasale AL (2006) Bronchodilators for bronchiolitis. Cochrane Database Syst Rev
3: CD001266
Gal P, Ransom JL, Davis SA (2006) Possible ibuprofen-induced kernicterus in a near-term infant
with moderate hyperbilirubinemia. J Pediatr Pharmacol Ther 11:245–250
Glass HC, Wirrell E (2009) Controversies in neonatal seizure management. J Child Neurol
24:591–599
Goto S, Seo T, Murata T, Nakada N, Ueda N, Ishitsu T, Nakagawa K (2007) Population estimation
of the effects of cytochrome P450 2C9 and 2C19 polymorphisms on phenobarbital clearance in
Japanese. Ther Drug Monit 29:118–121
Green TP, Thompson TR, Johnson DE, Lock JE (1983) Diuresis and pulmonary function in
premature infants with respiratory distress syndrome. J Pediatr 103:618–623
Guerrini R (2006) Epilepsy in children. Lancet 367:499–524
Guignard JP (2002) The adverse renal effects of prostaglandin-synthesis inhibitors in the newborn
rabbit. Semin Perinatol 26:398–405
Hammerman C, Glaser J, Kaplan M, Schimmel MS, Ferber B, Eidelman AI (1998) Indomethacin
tocolysis increases postnatal patent ductus arteriosus severity. Pediatrics 102:E56
Hammerman C, Shchors I, Jacobson S, Schimmel MS, Bromiker R, Kaplan M, Nir A (2008)
Ibuprofen versus continuous indomethacin in premature neonates with patent ductus
arteriosus: is the difference in the mode of administration? Pediatr Res 64:291–297
Hartley R, Green M, Quinn MW, Rushforth JA, Levene MI (1994) Development of morphine
glucuronidation in premature neonates. Biol Neonate 66:1–9
Hausner E, Fiszman ML, Hanig J, Harlow P, Zornberg G, Sobel S (2008) Long-term consequences
of drugs on the paediatric cardiovascular system. Drug Saf 31:1083–1096
Hellstr€om A, Ley D, Hansen-Pupp I, Niklasson A, Smith L, Lofqvist C, Hard AL (2009) New
insights into the development of retinopathy of prematurity – importance of early weight gain.
Acta Paediatr 99:502–508
Hendeles L, Weinberger M (1983) Theophylline. A “state of the art” review. Pharmacotherapy
3:2–44
Hohmeister J, Kroll A, Wollgarten-Hadamek I, Zohsel K, Demirakca S, Hermann C (2010)
Cerebral processing of pain in school-age children with neonatal nociceptive input: an explor-
atory fMRI study. Pain 150:257–267
Holmes GL (2009) The long-term effects of neonatal seizures. Clin Perinatol 36:901–914
Holmstr€om G, van Wijngaarden P, Coster DJ, Williams KA (2007) Genetic susceptibility to
retinopathy of prematurity: the evidence from clinical and experimental animal studies. Br J
Ophthalmol 91:1704–1708
Holopainen IE (2008) Seizures in the developing brain: cellular and molecular mechanisms of
neuronal damage, neurogenesis and cellular reorganization. Neurochem Int 52:935–947
Holt PG, Upham JW, Sly PD (2005) Contemporaneous maturation of immunologic and respiratory
functions during early childhood: implications for development of asthma prevention
strategies. J Allergy Clin Immunol 116:16–24
Honda A, Sugimoto Y, Namba T, Watabe A, Irie A, Negishi M, Narumiya S, Ichikawa A (1993)
Cloning and expression of a cDNA for mouse prostaglandin E receptor EP2 subtype. J Biol
Chem 268:7759–7762
Hunt CE (2006) Ontogeny of autonomic regulation in late preterm infants born at 34–37 weeks
postmenstrual age. Semin Perinatol 30:73–76
Hunt CE, Hauck FR (2007) Sudden infant death syndrome. In: Kliegman RM, Behrman RE,
Philadelphia
Huss M, H€olling H, Kurth BM, Schlack R (2008) How often are German children and adolescents
diagnosed with ADHD? Prevalence based on the judgment of health care professionals: results
of the German health and examination survey (KiGGS). Eur Child Adolesc Psychiatry
17(Suppl 1):52–58
Hussain T, Greenhalgh K, McLeod KA (2009) Hypoglycaemic syncope in children secondary to
beta-blockers. Arch Dis Child 94:968–969
Irwin CE Jr (2003) Somatic growth and development during adolescence. In: Rudolph CD,
Rudolph AM, Hostetter MK, Lister G, Siegel NJ (eds) Rudolph’s pediatrics, 21st edn. McGraw
Hill Medical, New York
Jain A, Agarwal R, Sankar MJ, Deorari AK, Paul VK (2008a) Hypocalcemia in the newborn.
Indian J Pediatr 75:165–169
Jain A, Aggarwal R, Jeevasanker M, Agarwal R, Deorari AK, Paul VK (2008b) Hypoglycemia in
the newborn. Indian J Pediatr 75:63–67
Jeck N, Schlingmann KP, Reinalter SC, Komhoff M, Peters M, Waldegger S, Seyberth HW (2005)
Salt handling in the distal nephron: lessons learned from inherited human disorders. Am J
Physiol Regul Integr Comp Physiol 288:R782–R795
Johnson TN, Thomson M (2008) Intestinal metabolism and transport of drugs in children: the
effects of age and disease. J Pediatr Gastroenterol Nutr 47:3–10
Johnson TN, Tanner MS, Taylor CJ, Tucker GT (2001) Enterocytic CYP3A4 in a paediatric
population: developmental changes and the effect of coeliac disease and cystic fibrosis. Br J
Clin Pharmacol 51:451–460
Kadan-Lottick NS (2007) Epidemiology of childhood and adolescent cancer. In: Kliegman RM,
Kanabar D, Dale S, Rawat M (2007) A review of ibuprofen and acetaminophen use in febrile
children and the occurrence of asthma-related symptoms. Clin Ther 29:2716–2723
Kauffman RE (2005) Drug action and therapy in infants and children. In: Yaffe SJ, Aranda JV
(eds) Neonatal and pediatric pharmacology – therapeutic principles in practice, 3rd edn.
Lippincott Williams & Wilkins, Philadelphia
Kauffman RE, Lieh-Lai M (2004) Ibuprofen and increased morbidity in children with asthma: fact
or fiction? Paediatr Drugs 6:267–272
Kauffman RE, Nelson MV (1992) Effect of age on ibuprofen pharmacokinetics and antipyretic
response. J Pediatr 121:969–973
Kearns GL, Abdel-Rahman SM, Alander SW, Blowey DL, Leeder JS, Kauffman RE (2003)
Developmental pharmacology – drug disposition, action, and therapy in infants and children.
N Engl J Med 349:1157–1167
Kennedy M (2008) Hormonal regulation of hepatic drug-metabolizing enzyme activity during
adolescence. Clin Pharmacol Ther 84:662–673
Kermorvant-Duchemin E, Sapieha P, Sirinyan M, Beauchamp M, Checchin D, Hardy P, Sennlaub
F, Lachapelle P, Chemtob S (2010) Understanding ischemic retinopathies: emerging concepts
from oxygen-induced retinopathy. Doc Ophthalmol 120:51–60
Kerschner JE (2007) Otitis media. In: Kliegman RM, Behrman RE, Jenson HB, Stanton BF (eds)
Nelson textbook of pediatrics, 18th edn. Saunders Elsevier, Philadelphia
Kinney HC (2009) Brainstem mechanisms underlying the sudden infant death syndrome: evidence
from human pathologic studies. Dev Psychobiol 51:223–233
K€ockerling A, Reinalter SC, Seyberth HW (1996) Impaired response to furosemide in hyperpros-
taglandin E syndrome: evidence for a tubular defect in the loop of Henle. J Pediatr
129:519–528
Konduri GG, Kim UO (2009) Advances in the diagnosis and management of persistent pulmonary
hypertension of the newborn. Pediatr Clin North Am 56:579–600
Koren G, Boucher N (2009) Adverse effects in neonates exposed to SSRIs and SNRI in late
gestation – Motherisk update 2008. Can J Clin Pharmacol 16:e66–e67
Koukouritaki SB, Manro JR, Marsh SA, Stevens JC, Rettie AE, McCarver DG, Hines RN (2004)
Developmental expression of human hepatic CYP2C9 and CYP2C19. J Pharmacol Exp Ther
308:965–974
Kuhle S, Male C, Mitchell L (2003) Developmental hemostasis: pro- and anticoagulant systems
during childhood. Semin Thromb Hemost 29:329–338
L€aer S, Elshoff JP, Meibohm B, Weil J, Mir TS, Zhang W, Hulpke-Wette M (2005) Development
of a safe and effective pediatric dosing regimen for sotalol based on population pharmacoki-
netics and pharmacodynamics in children with supraventricular tachycardia. J Am Coll Cardiol
46:1322–1330
Lambert GH, Schoeller DA, Kotake AN, Flores C, Hay D (1986) The effect of age, gender, and
sexual maturation on the caffeine breath test. Dev Pharmacol Ther 9:375–388
Latasch L, Freye E (2002) Pain and opioids in preterm and newborns. Anaesthesist 51:272–284
Lebenthal A, Lebenthal E (1999) The ontogeny of the small intestinal epithelium. JPEN J Parenter
Enteral Nutr 23:S3–S6
Lenney W, Milner AD (1978) At what age do bronchodilator drugs work? Arch Dis Child
53:532–535
Leonhardt A, Seyberth HW (2003) Do we need another NSAID instead of indomethacin for
treatment of ductus arteriosus in preterm infants? Acta Paediatr 92:996–999
Leonhardt A, Glaser A, Wegmann M, Schranz D, Seyberth H, Nusing R (2003) Expression of
prostanoid receptors in human ductus arteriosus. Br J Pharmacol 138:655–659
Leonhardt A, Strehl R, Barth H, Seyberth HW (2004) High efficacy and minor renal effects of
indomethacin treatment during individualized fluid intake in premature infants with patent
ductus arteriosus. Acta Paediatr 93:233–240
Leung DYM (2007) Allergy and the immumologic basis of atopic disease. In: Kliegman RM,
Levene M (2007) Minimising neonatal brain injury: how research in the past five years has
changed my clinical practice. Arch Dis Child 92:261–265
Linday LA, Engle MA, Reidenberg MM (1981) Maturation and renal digoxin clearance. Clin
Linday LA, Drayer DE, Khan MA, Cicalese C, Reidenberg MM (1984) Pubertal changes in net
renal tubular secretion of digoxin. Clin Pharmacol Ther 35:438–446
Litalien C, Theoret Y, Faure C (2005) Pharmacokinetics of proton pump inhibitors in children.
Clin Pharmacokinet 44:441–466
Liu AH, Covar RA, Spahn JD, Leung DYM (2007) Childhood asthma. In: Kliegman RM,
Liu H, Manganiello V, Waleh N, Clyman RI (2008) Expression, activity, and function of
phosphodiesterases in the mature and immature ductus arteriosus. Pediatr Res 64:477–481
L€oscher W, Klotz U, Zimprich F, Schmidt D (2009) The clinical impact of pharmacogenetics on
the treatment of epilepsy. Epilepsia 50:1–23
Lowry JA, Jarrett RV, Wasserman G, Pettett G, Kauffman RE (2001) Theophylline toxicokinetics
in premature newborns. Arch Pediatr Adolesc Med 155:934–939
Lynn AM, Nespeca MK, Opheim KE, Slattery JT (1993) Respiratory effects of intravenous
morphine infusions in neonates, infants, and children after cardiac surgery. Anesth Analg
77:695–701
Madadi P, Ross CJ, Hayden MR, Carleton BC, Gaedigk A, Leeder JS, Koren G (2009) Pharmaco-
genetics of neonatal opioid toxicity following maternal use of codeine during breastfeeding: a
case-control study. Clin Pharmacol Ther 85:31–35
Mandelli M, Tognoni G, Garattini S (1978) Clinical pharmacokinetics of diazepam. Clin
Marcell AB, Irwin CE Jr (2003a) Risk-taking behaviors: substance use and abuse. In: Rudolph CD,
Marcell AB, Irwin CE Jr (2003b) Risk-taking behaviors: unintentional injuries. In: Rudolph CD,
Marcell AV, Irwin CE Jr (2003c) Risk-taking behaviors: sexual behavior. In: Rudolph CD,
Marcell AV, Irwin, Jr CE (2003d) Risk-taking behaviors: covariation of risk behavoirs. In:
Rudolph CD, Rudolph AM, Hostetter MK, Lister G, Siegel NJ (eds) Rudolph’s Pediatrics,
21st edn. McGraw Hill Medical, New York
Marshall JD, Kearns GL (1999) Developmental pharmacodynamics of cyclosporine. Clin
McCracken GH Jr (1986) Aminoglycoside toxicity in infants and children. Am J Med 80:172–178
McIlleron H, Willemse M, Werely CJ, Hussey GD, Schaaf HS, Smith PJ, Donald PR (2009)
Isoniazid plasma concentrations in a cohort of South African children with tuberculosis:
implications for international pediatric dosing guidelines. Clin Infect Dis 48:1547–1553
Miki Y, Suzuki T, Tazawa C, Blumberg B, Sasano H (2005) Steroid and xenobiotic receptor
(SXR), cytochrome P450 3A4 and multidrug resistance gene 1 in human adult and fetal tissues.
Mol Cell Endocrinol 231:75–85
Miller ML (2007) Evaluation of suspected rheumatic disease. In: Kliegman RM, Behrman RE,
Philadelphia
Mirochnick MH, Miceli JJ, Kramer PA, Chapron DJ, Raye JR (1988) Furosemide pharmacokinet-
ics in very low birth weight infants. J Pediatr 112:653–657
Momma K, Toyoshima K, Takeuchi D, Imamura S, Nakanishi T (2005a) In vivo reopening of the
neonatal ductus arteriosus by a prostanoid EP4-receptor agonist in the rat. Prostaglandins Other
Lipid Mediat 78:117–128
Momma K, Toyoshima K, Takeuchi D, Imamura S, Nakanishi T (2005b) In vivo constriction of
the fetal and neonatal ductus arteriosus by a prostanoid EP4-receptor antagonist in rats. Pediatr
Res 58:971–975
Momma K, Toyoshima K, Ito K, Sugiyama K, Imamura S, Sun F, Nakanishi T (2009) Delayed
neonatal closure of the ductus arteriosus following early in utero exposure to indomethacin in
the rat. Neonatology 96:69–79
Moscicki AB (2003) Common menstrual problems. In: Rudolph CD, Rudolph AM, Hostetter MK,
Lister G, Siegel NJ (eds) Rudolph’s pediatrics, 21st edn. McGraw Hill Medical, New York
Mulrooney DA, Yeazel MW, Kawashima T, Mertens AC, Mitby P, Stovall M, Donaldson SS,
Green DM, Sklar CA, Robison LL, Leisenring WM (2009) Cardiac outcomes in a cohort of
adult survivors of childhood and adolescent cancer: retrospective analysis of the Childhood
Cancer Survivor Study cohort. BMJ 339:b4606
Murry DJ, Crom WR, Reddick WE, Bhargava R, Evans WE (1995) Liver volume as a determinant
of drug clearance in children and adolescents. Drug Metab Dispos 23:1110–1116
Nakanishi T, Gu H, Hagiwara N, Momma K (1993) Mechanisms of oxygen-induced contraction of
ductus arteriosus isolated from the fetal rabbit. Circ Res 72:1218–1228
Narayanan M, Schlueter M, Clyman RI (1999) Incidence and outcome of a 10-fold indomethacin
overdose in premature infants. J Pediatr 135:105–107
Natarajan G, Botica ML, Thomas R, Aranda JV (2007) Therapeutic drug monitoring for caffeine
in preterm neonates: an unnecessary exercise? Pediatrics 119:936–940
Neu J (2007) Gastrointestinal development and meeting the nutritional needs of premature infants.
Am J Clin Nutr 85:629S–634S
Nissen SE (2006) ADHD drugs and cardiovascular risk. N Engl J Med 354:1445–1448
No authors listed (2004) Morbidity and mortality among outborn neonates at 10 tertiary care
institutions in India during the year 2000. J Trop Pediatr 50:170–174
Norton ME, Merrill J, Cooper BA, Kuller JA, Clyman RI (1993) Neonatal complications after the
administration of indomethacin for preterm labor. N Engl J Med 329:1602–1607
Ohlsson A, Walia R, Shah S (2008) Ibuprofen for the treatment of patent ductus arteriosus in
preterm and/or low birth weight infants. Cochrane Database Syst Rev: CD003481
Olkkola KT, Maunuksela EL, Korpela R, Rosenberg PH (1988) Kinetics and dynamics of
postoperative intravenous morphine in children. Clin Pharmacol Ther 44:128–136
Pacifici GM (2009) Clinical pharmacokinetics of aminoglycosides in the neonate: a review. Eur J
Paradisis M, Evans N, Kluckow M, Osborn D (2009) Randomized trial of milrinone versus placebo
for prevention of low systemic blood flow in very preterm infants. J Pediatr 154:189–195
Paus T, Keshavan M, Giedd JN (2008) Why do many psychiatric disorders emerge during
adolescence? Nat Rev Neurosci 9:947–957
Peters M, Jeck N, Reinalter S, Leonhardt A, Tonshoff B, Klaus GG, Konrad M, Seyberth HW
(2002) Clinical presentation of genetically defined patients with hypokalemic salt-losing
tubulopathies. Am J Med 112:183–190
Peterson RG, Simmons MA, Rumack BH, Levine RL, Brooks JG (1980) Pharmacology of
furosemide in the premature newborn infant. J Pediatr 97:139–143
Pons G, Rey E, Carrier O, Richard MO, Moran C, Badoual J, Olive G (1989) Maturation of AFMU
excretion in infants. Fundam Clin Pharmacol 3:589–595
Powers PS, Bruty H (2009) Pharmacotherapy for eating disorders and obesity. Child Adolesc
Psychiatr Clin N Am 18:175–187
Prevot A, Mosig D, Guignard JP (2002) The effects of losartan on renal function in the newborn
rabbit. Pediatr Res 51:728–732
Raishevich N, Jensen P (2007) Attention-deficit/hyperactivity disorder. In: Kliegman RM,
Raju TN, Higgins RD, Stark AR, Leveno KJ (2006) Optimizing care and outcome for late-preterm
(near-term) infants: a summary of the workshop sponsored by the National Institute of Child
Health and Human Development. Pediatrics 118:1207–1214
Ramachandrappa A, Jain L (2009) Health issues of the late preterm infant. Pediatr Clin North Am
56:565–577
Rane A (2005) Drug metabolism and disposition in infants and children. Neonatal and pediatric
pharmacology – therapeutic principles in practice, 3rd edn. Lippincott Williams and Wilkins,
Philadelphia
Redmond GP, Bell JJ, Perel JM (1978) Effect of human growth hormone on amobarbital metabo-
lism in children. Clin Pharmacol Ther 24:213–218
Reed MD, Rodarte A, Blumer JL, Khoo KC, Akbari B, Pou S, Pharmd KGL (2001) The single-
dose pharmacokinetics of midazolam and its primary metabolite in pediatric patients after oral
and intravenous administration. J Clin Pharmacol 41:1359–1369
Reese J, Waleh N, Poole SD, Brown N, Roman C, Clyman RI (2009) Chronic in utero cyclooxy-
genase inhibition alters PGE2-regulated ductus arteriosus contractile pathways and prevents
postnatal closure. Pediatr Res 66:155–161
Reinalter SC, Jeck N, Peters M, Seyberth HW (2004) Pharmacotyping of hypokalaemic salt-losing
tubular disorders. Acta Physiol Scand 181:513–521
Roan Y, Galant SP (1982) Decreased neutrophil beta adrenergic receptors in the neonate. Pediatr
Res 16:591–593
Rodrigues AD (2005) Impact of CYP2C9 genotype on pharmacokinetics: are all cyclooxygenase
inhibitors the same? Drug Metab Dispos 33:1567–1575
Sankar R, Painter MJ (2005) Neonatal seizures: after all these years we still love what doesn’t
work. Neurology 64:776–777
Sans V, de la Dumas RE, Berge J, Grenier N, Boralevi F, Mazereeuw-Hautier J, Lipsker D, Dupuis
E, Ezzedine K, Vergnes P, Taieb A, Leaute-Labreze C (2009) Propranolol for severe infantile
hemangiomas: follow-up report. Pediatrics 124:e423–e431
Satwani P, Morris E, van de Ven C, Cairo MS (2005) Dysregulation of expression of immunoreg-

ulatory and cytokine genes and its association with the immaturity in neonatal phagocytic and
cellular immunity. Biol Neonate 88:214–227
Schindler M (2002) Do bronchodilators have an effect on bronchiolitis? Crit Care 6:111–112
Schuster V, von Stockhausen HB, Seyberth HW (1990) Effects of highly overdosed indomethacin
in a preterm infant with symptomatic patent ductus arteriosus. Eur J Pediatr 149:651–653
Seyberth HW (2008) An improved terminology and classification of Bartter-like syndromes. Nat
Clin Pract Nephrol 4:560–567
Seyberth HW, K€uhl PG (1988) The role of eicosanoids in paediatrics. Eur J Pediatr 147:341–349
Seyberth HW, Rascher W, Hackenthal R, Wille L (1983) Effect of prolonged indomethacin
therapy on renal function and selected vasoactive hormones in very-low-birth-weight infants
with symptomatic patent ductus arteriosus. J Pediatr 103:979–984
Seyberth HW, M€uller H, Ulmer HE, Wille L (1984) Urinary excretion rates of 6-keto-PGF1 alpha
in preterm infants recovering from respiratory distress with and without patent ductus
arteriosus. Pediatr Res 18:520–524
Seyberth HW, Leonhardt A, T€ onshoff B, Gordjani N (1991) Prostanoids in paediatric kidney
diseases. Pediatr Nephrol 5:639–649
Shankaran S, Kauffman RE (1984) Use of chloramphenicol palmitate in neonates. J Pediatr
105:113–116
Shirkey HC (1975) Pediatric therapy, 5th edn. The C.V. Mosby Company, Saint Louis
Sj€oqvist F, Garle M, Rane A (2008) Use of doping agents, particularly anabolic steroids, in sports
and society. Lancet 371:1872–1882
Slotkin TA, Auman JT, Seidler FJ (2003) Ontogenesis of beta-adrenoceptor signaling:
implications for perinatal physiology and for fetal effects of tocolytic drugs. J Pharmacol
Exp Ther 306:1–7
Smith GC (1998) The pharmacology of the ductus arteriosus. Pharmacol Rev 50:35–58
Smith GC, McGrath JC (1994) Interactions between indomethacin, noradrenaline and vasodilators
in the fetal rabbit ductus arteriosus. Br J Pharmacol 111:1245–1251
Smith GC, Wu WX, Nijland MJ, Koenen SV, Nathanielsz PW (2001) Effect of gestational age,
corticosteroids, and birth on expression of prostanoid EP receptor genes in lamb and baboon
ductus arteriosus. J Cardiovasc Pharmacol 37:697–704
Steer PA, Henderson-Smart DJ (2000) Caffeine versus theophylline for apnea in preterm infants.
Cochrane Database Syst Rev: CD000273
Stevens TP, Harrington EW, Blennow M, Soll RF (2007) Early surfactant administration with
brief ventilation vs. selective surfactant and continued mechanical ventilation for preterm
infants with or at risk for respiratory distress syndrome. Cochrane Database Syst Rev:
CD003063
Stewart CF, Hampton EM (1987) Effect of maturation on drug disposition in pediatric patients.
Clin Pharm 6:548–564
Strolin BM, Whomsley R, Baltes EL (2005) Differences in absorption, distribution, metabolism
and excretion of xenobiotics between the paediatric and adult populations. Expert Opin Drug
Metab Toxicol 1:447–471
Subbarao P, Ratjen F (2006) Beta2-agonists for asthma: the pediatric perspective. Clin Rev
Allergy Immunol 31:209–218
Szabó EZ, Luginbuehl I, Bissonnette B (2009) Impact of anesthetic agents on cerebrovascular
physiology in children. Paediatr Anaesth 19:108–118
Taddio A, Katz J, Ilersich AL, Koren G (1997) Effect of neonatal circumcision on pain response
during subsequent routine vaccination. Lancet 349:599–603
Takahashi H, Ishikawa S, Nomoto S, Nishigaki Y, Ando F, Kashima T, Kimura S, Kanamori M,
Echizen H (2000) Developmental changes in pharmacokinetics and pharmacodynamics of
warfarin enantiomers in Japanese children. Clin Pharmacol Ther 68:541–555
Tanner JM, Davies PS (1985) Clinical longitudinal standards for height and height velocity for
North American children. J Pediatr 107:317–329
Thébaud B, Michelakis ED, Wu XC, Moudgil R, Kuzyk M, Dyck JR, Harry G, Hashimoto K,
Haromy A, Rebeyka I, Archer SL (2004) Oxygen-sensitive Kv channel gene transfer confers
oxygen responsiveness to preterm rabbit and remodeled human ductus arteriosus: implications
for infants with patent ductus arteriosus. Circulation 110:1372–1379
Thompson AM, Bizzarro MJ (2008) Necrotizing enterocolitis in newborns: pathogenesis, preven-
tion and management. Drugs 68:1227–1238
Tobin JR (2008) Paradoxical effects of midazolam in the very young. Anesthesiology 108:6–7
Toyoshima K, Momma K, Imamura S, Nakanishi T (2006) In vivo dilatation of the fetal and
postnatal ductus arteriosus by inhibition of phosphodiesterase 3 in rats. Biol Neonate
89:251–256
Tubergen DG, Bleyer A (2007) The leukemias. In: Kliegman RM, Behrman RE, Jenson HB,
Stanton BF (eds) Nelson textbook of pediatrics, 18th edn. Saunders Elsevier, Philadelphia
Vogelstein B, Kowarski A, Lietman PS (1977) The pharmacokinetics of amikacin in children. J
Pediatr 91:333–339
Waleh N, Kajino H, Marrache AM, Ginzinger D, Roman C, Seidner SR, Moss TJ, Fouron JC,
Vazquez-Tello A, Chemtob S, Clyman RI (2004) Prostaglandin E2 – mediated relaxation of
the ductus arteriosus: effects of gestational age on g protein-coupled receptor expression,
signaling, and vasomotor control. Circulation 110:2326–2332
Waleh N, Reese J, Kajino H, Roman C, Seidner S, McCurnin D, Clyman RI (2009) Oxygen-
induced tension in the sheep ductus arteriosus: effects of gestation on potassium and calcium
channel regulation. Pediatr Res 65:285–290
Walker SM, Franck LS, Fitzgerald M, Myles J, Stocks J, Marlow N (2009) Long-term impact of
neonatal intensive care and surgery on somatosensory perception in children born extremely
preterm. Pain 141:79–87
Wang L, Pozzato V, Turato G, Madamanchi A, Murphy TM, Chitano P (2008) Reduced sponta-
neous relaxation in immature guinea pig airway smooth muscle is associated with increased
prostanoid release. Am J Physiol Lung Cell Mol Physiol 294:L964–L973
Wheatley CM, Dickinson JL, Mackey DA, Craig JE, Sale MM (2002) Retinopathy of prematurity:
recent advances in our understanding. Br J Ophthalmol 86:696–700
Whitsett JA, Noguchi A, Moore JJ (1982) Developmental aspects of alpha- and beta-adrenergic
receptors. Semin Perinatol 6:125–141
Witter FR, Zimmerman AW, Reichmann JP, Connors SL (2009) In utero beta 2 adrenergic agonist
exposure and adverse neurophysiologic and behavioral outcomes. Am J Obstet Gynecol
201:553–559
Wright DH, Abran D, Bhattacharya M, Hou X, Bernier SG, Bouayad A, Fouron JC, Vazquez-Tello
A, Beauchamp MH, Clyman RI, Peri K, Varma DR, Chemtob S (2001) Prostanoid receptors:
ontogeny and implications in vascular physiology. Am J Physiol Regul Integr Comp Physiol
281:R1343–R1360
Yaffe SJ, Friedman WF, Rogers D, Lang P, Ragni M, Saccar C (1980) The disposition of
indomethacin in preterm babies. J Pediatr 97:1001–1006
Yang D, Pearce RE, Wang X, Gaedigk R, Wan YJ, Yan B (2009) Human carboxylesterases HCE1
and HCE2: ontogenic expression, inter-individual variability and differential hydrolysis of
oseltamivir, aspirin, deltamethrin and permethrin. Biochem Pharmacol 77:238–247
Developmental Pharmacokinetics
Johannes N. van den Anker, Matthias Schwab, and Gregory L. Kearns
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
2 Drug Absorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
2.1 The Gastrointestinal Tract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
3 The Skin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
4 Drug Distribution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
5 Drug Metabolism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
6 Phase I Enzymes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
6.1 CYP3A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
6.2 CYP1A2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
6.3 CYP2D6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
6.4 CYP2C9/CYP2C19 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 61
6.5 CYP2E1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
7 Drug Excretion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
8 Other Factors Influencing the Absorption, Distribution, Metabolism,
and Excretion of Drugs in Neonates and Young Infants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65
9 Pharmacogenomics: Impact for Pediatric Populations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 66
10 The Interface of Pharmacokinetics and Pharmacodynamics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67
11 Pediatric Dose Selection Based upon Pharmacokinetic Principles . . . . . . . . . . . . . . . . . . . . . . . 68
12 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 70
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71
J.N. van den Anker (*)

Division of Pediatric Clinical Pharmacology, Department of Pediatrics, Children’s National
Medical Center, 111 Michigan Avenue, NW, Washington, DC 20010, USA
e-mail: jvandena@cnmc.org
M. Schwab
Dr. Margarete Fischer-Bosch-Institute of Clinical Pharmacology, Auerbachstrasse 112,
70376 Stuttgart, Germany
Department of Clinical Pharmacology, Institute of Experimental and Clinical Pharmacology and
Toxicology, University Hospital, T€
ubingen, Germany
G.L. Kearns
Division of Pediatric Pharmacology and Medical Toxicology, Department of Medical Research,
Children’s Mercy Hospital, Kansas City, MO, USA

52 J.N. van den Anker et al.
Abstract The advances in developmental pharmacokinetics during the past decade

reside with an enhanced understanding of the influence of growth and development
on drug absorption, distribution, metabolism, and excretion (ADME). However,
significant information gaps remain with respect to our ability to characterize
the impact of ontogeny on the activity of important drug metabolizing enzymes,
transporters, and other targets. The ultimate goal of rational drug therapy in
neonates, infants, children, and adolescents resides with the ability to individualize
it based on known developmental differences in drug disposition and action. The
clinical challenge in achieving this is accounting for the variability in all of the
contravening factors that influence pharmacokinetics and pharmacodynamics (e.g.,
genetic variants of ADME genes, different disease phenotypes, disease progression,
and concomitant treatment). Application of novel technologies in the fields of
pharmacometrics (e.g., in silico simulation of exposure–response relationships;
disease progression modeling), pharmacogenomics and biomarker development
(e.g., creation of pharmacodynamic surrogate endpoints suitable for pediatric use)
are increasingly making integrated approaches for developmentally appropriate
dose regimen selection possible.
Keywords Developmental pharmacology • Pediatric pharmacology •

Neonatal pharmacology • Neonates • Pharmacokinetics • Pharmacogenomics •
Pharmacodynamics • Drug metabolizing enzymes
1 Introduction
Human growth and development consists of a continuum of biologic events that

includes somatic growth, neurobehavioral maturation, and eventual reproduction.
The impact of these developmental changes in drug disposition is largely related
to changes in body composition (e.g., body water content, plasma protein con-
centrations) and function of organs important in metabolism (e.g., the liver) and
excretion (e.g., the kidney). During the first decade of life, these changes are
dynamic and can be nonlinear and discordant making standardized dosing inade-
quate for effective drug dosing across the span of childhood. Consequently, “stan-
dard dosing” of many drugs during rapid phases of growth/development where
both drug disposition and response may be altered is generally inadequate for
the purpose of optimizing drug therapy. This goal can only be achieved through
fundamental and integrative understanding of how ontogeny influences pharmaco-
kinetics and pharmacodynamics.
Developmental pharmacokinetics must take into account normal growth and
developmental pathways (Bartelink et al. 2006; Johnson et al. 2006). A better
understanding of the various physiologic variables regulating and determining the
fate of drugs in the body and their pharmacologic effects has dramatically improved
both the safety and the efficacy of drug therapy for neonates, infants, children, and
Developmental Pharmacokinetics 53
adolescents (Kearns et al. 2003a; Van Den Anker and Rakhmanina 2006). The
impact of development on the pharmacokinetics of a given drug is dependent, to a
great degree, upon age-related changes in the body composition and the acquisition
of function of organs and organ systems that are important in determining drug
metabolism as well as drug transport and excretion (Edginton et al. 2006; Anderson
and Holford 2008). Although it is often convenient to classify pediatric patients
on the basis of postnatal age for the study and provision of drug therapy (e.g.,
newborn infants aged 1 month or less, infants between 1 and 24 months of age,
children between 2 and 12 years of age, and adolescents between 12 and
16–18 years of age), it is important to recognize that changes in physiology that
characterize development may not correspond to these age-defined breakpoints and
are also not linearly related to age. In fact, the most dramatic changes in drug
disposition occur during the first 12–18 months of life, when the acquisition of
organ function is most dynamic (Kearns et al. 2003a; Van Den Anker and
Rakhmanina 2006). Additionally, independent from developmental aspects, it is
important to mention that the pharmacokinetics of a given drug may be altered in
pediatric patients also due to intrinsic (e.g., genotype, inherited diseases) and/or
extrinsic (e.g., acquired diseases, diet, co-medication) factors that may occur during
the first months and years of life (Blake et al. 2006; Van Den Anker et al. 1994;
Allegaert et al. 2008; Leeder 2003; Krekels et al. 2007; Leeder et al. 2010). In
principle, however, these factors are also important for nonpediatric populations
such as adult geriatric patients. To study pediatric pharmacokinetics it is very useful
to examine the impact of development on those physiologic variables that govern
drug absorption, distribution, metabolism, and excretion (Bartelink et al. 2006;
Johnson et al. 2006; Edginton et al. 2006) which is summarized by the commonly
used term ADME.
2 Drug Absorption
For therapeutic agents administered by extravascular routes, the process of absorp-

tion is reflected by the ability of a drug to overcome chemical, physical, mechani-
cal, and biological barriers. Developmental differences in the physiologic
composition and function of these barriers can alter the rate and/or extent of
drug absorption (Kearns et al. 2003a; Van Den Anker and Rakhmanina 2006).
While factors influencing drug absorption are multifactorial in nature, develop-
mental changes in the absorptive surfaces (e.g., gastrointestinal tract, skin) can
be determinants of bioavailability (Kearns et al. 2003a; Van Den Anker and
Rakhmanina 2006). The peroral route is the principal means for drug administration
to infants, children, and adolescents but the skin represents an often overlooked, but
important organ for systemic drug absorption as well. Therefore, the drug absorp-
tion part of this chapter will focus on drug absorption from the gastrointestinal
tract and through the skin.
2.1 The Gastrointestinal Tract
The most important factors that influence drug absorption from the gastrointestinal
tract are related to the physiology of the stomach, intestine, and biliary tract. The pH
of the stomach is practically neutral at birth, decreases to around 3 within 48 h after
birth, returns to neutral over the next 24 h, and remains that way for the next 10 days
(Bartelink et al. 2006). Thereafter, it slowly declines again until it reaches adult
values at about 2 years of age. These initial changes do not occur in premature
infants, who seem to have little or no free acid during the first 14 days of life
(Bartelink et al. 2006). The time of gastric emptying is delayed in the period
immediately after birth for both full term and preterm neonates. It approaches
adult values within the first 6–8 months of life (Strolin Benedetti and Baltes
2003). Intestinal transit time is prolonged in neonates because of reduced motility
and peristalsis, but appears to be reduced in older infants as a result of increased
intestinal motility (Strolin Benedetti and Baltes 2003; Kearns 2000). Other factors
that may play a role in intestinal drug absorption are immaturity of the intestinal
mucosa leading to increased permeability, immature biliary function, high levels of
intestinal b-glucuronidase activity, reduced first-pass metabolism, maturation of
carrier mechanisms, and variable microbial colonization (Kearns 2000). These
developmental differences in the physiologic composition and function of these
organs can alter the rate and/or extent of drug absorption. Changes in intraluminal
pH can directly impact both drug stability and degree of ionization, thus influencing
the relative amount of drug available for absorption. Acid labile drugs such as
penicillin G and erythromycin are therefore more efficiently absorbed, whereas the
same changes in gastric pH (developmentally or caused by the use of proton pump
inhibitors) will result in clinically important decreases in the absorption of weak
organic acids such as phenobarbital and phenytoin, necessitating adjustment of the
amount of antiepileptic drug administered to the individual patient (Strolin
Benedetti and Baltes 2003). Additionally, the ability to solubilize and subsequently
absorb lipophilic drugs can be influenced by age-dependent changes in biliary
function. Immature conjugation and/or transport of bile salts into the intestinal
lumen results in low intraduodenal levels despite blood levels that exceed those
seen in adults. Gastric emptying time is prolonged throughout infancy and child-
hood consequent to reduced motility, which may retard drug passage into the
intestine where the majority of absorption takes place (Kearns 2000). As a conse-
quence, the rate of absorption of drugs with limited water solubility such as
phenytoin and carbamazepine can be significantly altered resulting from these
changes in gastrointestinal motility. Unfortunately, few studies have systematically
evaluated the effect of developmental changes in gastric emptying and intestinal
motility on drug absorption in infants and children. Anderson et al. showed that
the oral acetaminophen (paracetamol) absorption rate was significantly lower in
the first days of life before stabilizing 1 week after birth (Anderson et al. 2002).
Another study showed that the time to reach the maximum concentration (tmax) of
cisapride was significantly longer in preterm infants compared with term neonates
(Kearns et al. 2003b). Generally, the rate at which most drugs are absorbed is
generally slower and thus, the time to achieve maximum plasma concentrations is
prolonged in neonates and young infants relative to older infants and children.
Despite their incomplete characterization, developmental differences in the activity
of intestinal drug metabolizing enzymes and efflux transporters have the potential
to markedly alter drug bioavailability.
3 The Skin
The morphologic and functional development of the skin as well as the factors that
influence penetration of drugs into and through the skin has been reviewed (Radde
and McKercher 1985). Basically, the percutaneous absorption of a compound
is directly related to the degree of skin hydration and relative absorptive surface
area and inversely related to the thickness of the stratum corneum (Radde and
McKercher 1985). The integument of the full-term neonate possesses an intact
barrier function and is similar to that of an older child or adolescent. However, the
ratio of surface area to body weight of the full-term neonate is much higher than that
of an adult. Thus, the infant will be exposed to a relatively greater amount of drug
topically than will older infants, children, or adolescents. In contrast, data of human
skin from preterm infants indicates an inverse correlation between permeability and
gestational age (Nachman and Esterly 1980). Permeability rates were 100- to 1,000-
fold greater before 30 weeks gestation as compared with full-term neonates, with a
three to fourfold greater permeation rate seen beyond 32 weeks (Ginsberg et al.
2004). In vivo studies suggest that this increased dermal permeability in preterm
infants is a short-lived phenomenon with the permeability barrier of even the most
premature neonates similar to that of full-term neonates by 2 weeks of postnatal life
(Ginsberg et al. 2004). There are numerous reports in the literature underscoring
the importance of skin absorption in neonates primarily showing toxicity after
exposure to drugs or chemicals. These include pentachlorophenol-containing laun-
dry detergents and hydrocortisone (Armstrong et al. 1969; Feinblatt et al. 1966).
Therefore, extreme caution needs to be exercised in using topical therapy in
neonates and young infants. In contrast, the possibility of turning enhanced skin
absorption of drugs to the infant’s advantage is an interesting idea and was explored
exemplarily several years ago by using the percutaneous route to administer
theophylline in preterm infants (Evans et al. 1985). A standard dose of theophylline
gel was applied and serial theophylline levels were measured demonstrating that
therapeutic theophylline levels were achieved in 11 of 13 infants and that the
percutaneous route is a feasible method of administering theophylline in preterm
infants.
4 Drug Distribution
Drug distribution is influenced by a variety of drug-specific physiochemical factors,

including the role of drug transporters, blood/tissue protein binding, blood and
tissue pH, and perfusion (Bartelink et al. 2006; Kearns et al. 2003a; Van Den
Anker and Rakhmanina 2006). However, age-related changes in drug distribution
are primarily related to developmental changes in body composition, the concen-
tration of available binding proteins, and the capacity of plasma proteins to bind
drugs. Age-dependent changes in body composition alter the physiologic “spaces”
into which a drug may distribute (Friis-Hansen 1983). In very young infants, the
total body water is high (80–90% of the bodyweight) while fat content is low
(10–15% of the bodyweight). The amount of total body water decreases to 55–60%
by adulthood. The extracellular water content is about 45% of the bodyweight in
neonates, compared with 20% in adulthood (Friis-Hansen 1983). Larger extracel-
lular and total body water spaces in neonates and young infants, coupled with
adipose stores that have a higher water/lipid ratio than in adults, produce lower
plasma concentrations for drugs that distribute into these respective compartments
when administered in a weight-based fashion. Several hydrophilic drugs such
as gentamicin and linezolid have a significantly larger volume of distribution in
neonates than in infants or adults (Kearns et al. 2003c; De Hoog et al. 2005). The
larger volume of distribution in neonates correlates with a larger extracellular water
content. The pharmacokinetics of tramadol, a hydrophilic compound with a large
volume of distribution in adults, could be described with a two-compartment model
(Allegaert et al. 2005). The volume of distribution of the central compartment (a
compartment more or less correlated to the extracellular water content) was
increased in neonates compared to older children. The volume of distribution of
the peripheral compartment (in which the drug is bound to tissue) was not affected
by age (Allegaert et al. 2005). For lipophilic drugs that associate primarily with
tissue, the influence of age on altering the apparent volume of distribution is not as
readily apparent. The extent of drug binding to proteins in the plasma may influence
the volume of distribution of drugs (Bartelink et al. 2006). Only free, unbound, drug
can be distributed from the vascular space into other body fluids and, ultimately, to
tissues where drug–receptor interaction occurs. Albumin, total protein, and total
globulins such as a1 acid-glycoprotein are the most important circulating proteins
responsible for this drug binding in plasma. The absolute concentration of these
proteins is influenced by age, nutrition, and disease. Changes in the composition
and amount of these circulating plasma proteins can also influence the distribution
of highly bound drugs (Bartelink et al. 2006; Edginton et al. 2006). A reduction in
both the quantity and binding affinity of circulating plasma proteins in the neonate
and young infant often produces an increase in the free fraction of drug, thereby
influencing the availability of the active moiety and potentially, its subsequent
hepatic and/or renal clearance. Other factors associated with development and/or
disease such as variability in regional blood flow, organ perfusion, permeability
of cell membranes, changes in acid–base balance, and cardiac output can also
influence drug binding and/or distribution. Finally, drug transporters such as

the ABC efflux pump P-glycoprotein (MDR1/ABCB1), which show not only an
ontogenic profile in the small intestine but also in the lung, can influence drug
distribution because these transporters can markedly influence the extent to which
drugs cross membranes in the body and whether drugs can penetrate or are secreted
from the target sites (e.g., cerebrospinal fluid).
5 Drug Metabolism
Drug metabolism reflects the biotransformation of an endogenous or exogenous

molecule by one or more enzymes to moieties, which are more hydrophilic and thus
can be more easily excreted (Bartelink et al. 2006; Kearns et al. 2003a; Van Den
Anker and Rakhmanina 2006). While metabolism of a drug generally reduces its
ability to produce a pharmacologic action, it also can result in a metabolite that has
significant potency, and thereby, contributes to the overall pharmacological effect
of the drug. In the case of a prodrug such as codeine, biotransformation is required
to produce the pharmacologically active metabolite morphine. Although drug
metabolism takes place in several tissues (e.g., intestine, skin, lungs, liver), hepatic
metabolism has been investigated most intensively and this metabolism has been
divided conventionally into two phases (Bartelink et al. 2006; Kearns et al. 2003a;
Van Den Anker and Rakhmanina 2006). Phase I hepatic metabolism usually results
in modifying the therapeutic agent or xenobiotic (e.g., through oxidation) in order
to make the molecule more polar. Phase II hepatic metabolism usually results in
addition of a small molecule (e.g., glucuronide) to the therapeutic agent in order to
make it more polar. While there are many enzymes that are capable of catalyzing
the biotransformation of drugs, the quantitatively most important are represented by
the cytochromes P450 (CYP450) (Nelson et al. 1996). The specific CYP450
isoforms responsible for the majority of human drug metabolism are represented
by CYP3A4/5, CYP1A2, CYP2B6, CYP2D6, CYP2C9, CYP2C19, and CYP2E1
(Brown et al. 2008).
Development has a profound effect on the expression of CYP450. Distinct
patterns of isoform-specific developmental CYP expression have been observed
postnatally. As reflected by recent reviews, distinct patterns of isoform-specific
developmental changes in drug biotransformation are apparent for many Phase I
and Phase II drug metabolizing enzymes (Hines and McCarver 2002; McCarver and
Hines 2002; De Wildt et al. 1999; Alcorn and McNamara 2002). Very recently,
Hines (Hines 2008) has categorized the development of enzymes involved in
human metabolism into three main categories: (1) those expressed during the
whole or part of the fetal period, but silenced or expressed at low levels within
1–2 years after birth; (2) those expressed at relatively constant levels through-
out fetal development, but increased to some extent postnatally; and (3) those
whose onset of expression can occur in the third trimester, but substantial increase
is noted in the first 1–2 years after birth. Based on literature data, CYP3A7,
Flavin-containing monooxygenase 1 (FMO1), sulfotransferase 1A3/4 (SULT1A3/4),

SULT1E1, and maybe alcohol dehydrogenase 1A (ADH1A) belong to the first
group. To the second group belong CYP2A6, 3A5, 2C9, 2C19, 2D6, 2E1, and
SULT1A1. The third group includes ADH1C, ADH1B, CYP1A1, 1A2, 2A 6, 2A7,
2B6, 2B7, 2C8, 2C9, 2F1, 3A4, FMO3, SULT2A1, glucoronosyltransferases
(UGT), and N-acetyltransferase 2 (Hines 2008; Balistreri et al. 1984; Card
et al. 1989).
In addition to these in vitro data, there has been an explosion in the amount of
information generated about metabolism of therapeutic agents in children during
the last two decades. In vivo data have been generated largely through two means
(Blake et al. 2005, 2007). One is through dedicated ontogeny studies in which
a probe drug (e.g., dextromethorphan or acetaminophen/paracetamol) is given to
children of various age groups or to the same children over a period of time (Blake
et al. 2005, 2007). The other manner in which these in vivo data have been
developed is serendipitously over the course of industry-sponsored or investiga-
tor-initiated pediatric clinical trials, which utilize the traditional age groups, and
both anticipated as well as unexpected results reveal new data about the drug
metabolizing enzymes involved. The most important examples of studies that
have resulted in clinically important insight into the ontogeny of drug metabolism
are summarized in the following paragraph.
Midazolam plasma clearance, which primarily reflects hepatic CYP3A4/5 activ-
ity after intravenous administration (De Wildt et al. 2001; Kinirons et al. 1999),
increases approximately fivefold (1.2–9 ml/min/kg) over the first 3 months of life
(Payne et al. 1989). Carbamazepine plasma clearance, also largely dependent upon
CYP3A4 (Kerr et al. 1994), is greater in children relative to adults (Pynn€onen et al.
1977; Riva et al. 1985; Rane et al. 1975), thereby necessitating higher weight-
adjusted (i.e., mg/kg) doses of the drug to produce therapeutic plasma concen-
trations. CYP2C9 and to a lesser extent, CYP2C19, are primarily responsible for
phenytoin biotransformation (Bajpai et al. 1996). Phenytoin apparent half life is
prolonged (~75 h) in preterm infants but decreases to ~20 h in term infants less than
1 week postnatal age and to ~8 h after 2 weeks of age (Loughnan et al. 1977).
Saturable phenytoin metabolism does not appear until approximately 10 days of
postnatal age, demonstrating the developmental acquisition of CYP2C9 activity.
Caffeine and theophylline are the most common CYP1A2 substrates used in
pediatrics. Caffeine elimination in vivo mirrors that observed in vitro with full
3-demethylation activity (mediated by CYP1A2) observed by approximately
4 months of age (Aranda et al. 1979). Formation of CYP1A2-dependent theophyl-
line metabolites reaches adult levels by approximately 4–5 months of postnatal age
(Kraus et al. 1993), and in older infants and young children, theophylline plasma
clearance generally exceeds adult values (Milavetz et al. 1986). Furthermore,
caffeine 3-demethylation in adolescent females appears to decline to adult levels
at Tanner stage II relative to males where it occurs at stages IV/V, thus
demonstrating an apparent sex difference in the ontogeny of CYP1A2.
The following sections of this chapter will focus on neonates and young infants
because no other group defines such a period of rapid growth and development. It is
well established that infants who are barely into their second trimester of gesta-
tional life born as small as a few hundred grams (400–500 g) can survive. On the
other extreme, by the end of the first month of postnatal life, large for gestational
age infants may weigh upwards of several kilograms. Indeed, the 95th weight
percentile is approximately 5 kg. No other age groups can be defined in differences
measured logarithmically. As one might expect, there are similar tremendous
developmental changes in hepatic drug metabolizing enzymes during this time
frame. Understanding these implications is important for individualized clinical
development programs.
6 Phase I Enzymes
6.1 CYP3A
The CYP3A subfamily represents the majority of CYP total content in the liver
(Brown et al. 2008). Indeed, it has been shown that over one-half of all drugs
prescribed are metabolized by CYP3A (Zanger et al. 2008). The CYP3A subfamily
consists of CYP3A4, 3A5, 3A7, and 3A43. CYP3A43 is not known to play a
significant role in hepatic metabolism. It has been established that CYP3A4 is
the predominant CYP3A enzyme in adults, whereas CYP3A7 is the predominant
CYP3A enzyme in the fetus and infants. Moreover, there is a great deal of overlap
of specificity of ability for CYP3A4 and CYP3A7 to metabolize therapeutic agents.
In 2003, Stevens et al. published the results of examining the largest collection of
fetal and pediatric liver samples to date. The study included 212 samples. Stevens
and colleagues demonstrated that CYP3A7 is highest between 94 and 168
postconceptional days on a pmol/mg basis of total hepatic protein (Stevens et al.
2003). The level at birth is less than half that of the high prenatal value. However, it
remains higher than that of even adult CYP3A4 levels. Furthermore, these hepatic
samples demonstrated that there is minimal CYP3A4 activity prenatally that
continues to increase after birth. Nevertheless, CYP3A7 content remains higher
than CYP3A4 content until at least 6 months of age.
To date, two probe drugs have been researched extensively, which have
demonstrated the lower activity of CYP3A4 at birth and in neonates. In 2001,
De Wildt et al. published the results of midazolam metabolism given to 24 preterm
infants. Only 19 of 24 preterm infants produced detectable levels of 1-OH-
midazolam. Furthermore, these results firmly established that premature infants
had lower CYP3A4 activity than full-term infants, than did children and adults
historically. Oral cisapride has also been demonstrated to be a suitable substrate
for CYP3A4 activity (Kearns et al. 2003b). Cisapride has demonstrated a similarly
low activity for CYP3A4 in the neonatal period, as did midazolam (Kearns et al.
2003b; De Wildt et al. 2001).
In conclusion, CYP3A7 activity is very high before birth and continues to have
high activity after birth and is even present into adulthood. CYP3A4 possesses very
low activity at birth and very slowly increases in the neonatal period. Thus, when
designing studies with substrates for CYP3A4 in young infants and children, great
care needs to be taken to adjust for this low activity in order to achieve the goal of
the FDA guidance that in children exposure and Cmax are not higher than that in
adults.
6.2 CYP1A2
One of the first CYP enzymes to be studied utilizing a probe drug in the first year
of life is CYP1A2. Two methylxanthines (caffeine and theophylline) have been
utilized extensively to evaluate CYP1A2 in vivo in young children (Evans et al.
1989; Erenberg et al. 2000; Lambert et al. 1986; Tateishi et al. 1999). Theophylline
and caffeine are two commonly utilized medications in neonates for the treatment
of apnea. These medications are frequently continued form the neonatal period
during the first year of life. At birth, caffeine-3-demethylation, a measure of
CYP1A2 activity, is very low. Consequently, Erenberg et al. published that the
efficacious dose of caffeine is 10 mg/kg every day (Erenberg et al. 2000). The half-
life of caffeine is 72–96 h in infants compared to approximately 5 h in older
children and adults. Similarly, 8-hydroxylation of theophylline is reduced at birth.
Nevertheless, longitudinal data indicate a rapid maturation process for CYP1A2, as
it appears to reach adult levels within the first year of life, often within the first
6 months of life. Finally, it is important to note that caffeine activity is highly
inducible by drugs, diet, and exogenous toxins such as cigarette smoke. In the adult
literature, variability in CYP1A2 activity up to 100-fold has been reported. More-
over, Blake et al. reported that caffeine elimination half-life in neonates who are
breast-fed is longer than that of formula-fed infants (Blake et al. 2006); information
which suggests that the composition of infant diet (i.e., an environmental factor)
can influence the pattern of ontogenic expression of a drug metabolizing enzyme.
In conclusion, it is evident that CYP1A2 activity is highly reduced in young
infants. Additionally, activity of the enzyme is highly inducible. Finally, maturation
of CYP1A2 activity is rapid in the first year of life. Therefore, when designing
clinical studies, which include neonates, great care must be taken to assure that
this variability in drug response is properly assessed, especially within the first
6–12 months of life.
6.3 CYP2D6
CYP2D6 is one of the most polymorphically expressed enzymes in humans (Zanger

et al. 2004; Gaedigk et al. 2008). Some estimates indicate that fewer than 90% of
individuals are homozygous for the wild-type allele. In 1991, Treluyer et al.
published the results of liver samples from fetuses aged 17–40 weeks postconcep-
tion. These results demonstrated that the concentration of hepatic CYP2D6 protein
was very low or undetectable in these fetuses. This lack of CYP2D6 activity at birth
led to the hypothesis that birth-related events may trigger maturation of the enzyme.
In 2007, Blake et al. published in vivo results that provided further understanding of
CYP2D6 activity in the first year of life. These results came from dosing infants
with dextromethorphan at 0.5, 1, 2, 4, 6, and 12 months of age and measuring the
metabolites in urine. These dextromethorphan results demonstrate indeed that there
is low activity at birth, but that there is rapid acquisition of CYP2D6 activity in the
first year of life. Already within the first 2 weeks of life there is measurable
acquisition of CYP2D6 activity. Despite the discussion in the literature about the
fact that the increase in renal function might conceal the enzyme development
resulting in an apparent plateau of the metabolic ratio after 2 weeks (Johnson et al.
2008), very recent data show that an infant with a postmenstrual age of 52 weeks
has already mature hepatic CYP2D6 activity (Allegaert et al. 2011).
Taken together, these results demonstrate the need for careful pharmacokinetic
studies in infants and toddlers who are provided a pharmacologic agent, which is
primarily metabolized by CYP2D6 (e.g., codeine, beta-blockers, propafenone). Not
only does one need to be cognizant of potential infants who are predestined by their
genome to be poor metabolizers, but potential studies need to realize the
implications of low levels of CYP2D6 at birth and also the rapid maturation process
that occurs within the first year of life (Stevens et al. 2008).
6.4 CYP2C9/CYP2C19
Lee et al. (2002) and Koukouritaki et al. (2004) have published the most extensive
reviews to date on CYP2C activity in humans. They demonstrate that the two main
representatives of the CYP2C subfamily of enzymes (CYP2C9 and CYP2C19)
conveniently follow the CYP2C rule of 20%. Approximately 20% of hepatic CYP
content of adult livers is CYP2C and these CYP2C enzymes metabolize 20% of
pharmaceuticals developed to date.
Although not to the same extent as CYP2D6, the two main CYP2C represen-
tatives are polymorphically expressed. To date, over 30 alleles of CYP2C9 of
CYP2C9 have been identified and more than 25 alleles of CYP2C19 of CYP2C19
have been reported in the literature (Lee et al. 2002; Koukouritaki et al. 2004). Just
as with CYP2D6, some of these polymorphisms may result in poor metabolizer
status, which may confound studies in infants and young children.
The ontogeny of CYP2C9 is much better established than CYP2C19. Indeed,
hepatic liver samples have shown that CYP2C9 activity is functionally very low
just prior to birth. However, much like CYP2D6, this activity increases quickly in
the first year of life. The classic example of the effects of this very low level of
CYP2C9 activity at birth can be seen with phenytoin (Suzuki et al. 1994). Indeed,
the recommended daily dose for newborns is 5 mg/kg/day, but by 6 months to

3 years of age this increases to 8–10 mg/kg/day consequent to increased CYP2C9
activity.
Two major pharmaceutical classes of drugs (i.e., benzodiazepines and proton
pump inhibitors) have major representative therapeutic agents that are metabolized
by CYP2C19 (Kearns et al. 2003d). Indeed, characteristic representatives from
these classes are used in the literature to indirectly ascertain the ontogeny of
CYP2C19 activity. Hydroxylation of diazepam is attributed to CYP2C19 activity
and is a classic example of the effects of the maturation process of CYP2C19 (Jung
et al. 1997). In neonates, the half-life of diazepam is reported to be 50–90 h. Within
the first year of life, that half-life of 40–50 h is much closer to the adult value, which
is reported as 20–50 h (Klotz 2007).
More recently, the effects of the ontogeny on proton pump inhibitor metabolism
have been reviewed. To date, all proton pump inhibitors other than rabeprazole
are metabolized by CYP2C19. Of the drugs in this class, the biotransformation
of pantoprazole is predominantly dependent upon CYP2C19 activity (Kearns and
Winter 2003). When the weight-normalized apparent oral clearance of pantoprazole
is examined in pediatric patients from 1 month to 16 years of age (Fig. 1), a
developmental profile for the acquisition of CYP2C19 activity is apparent. As
expected, exposures of the CYP2C19 metabolism-dependent proton pump
inhibitors are universally increased in the youngest infants when genetic
polymorphisms of CYP2C19 are fully accounted (Kearns and Winter 2003; Jung
et al. 1997).
Taken together, these results demonstrate an important trend when designing
pharmaceutical studies that depend on hepatic metabolism through the two major
CYP2C enzyme pathways. It is extremely important to be cognizant of the limited
activity of these enzymes in early childhood. Moreover, much like with CYP2D6, it
is important to recognize the impact of genetic polymorphisms when studying
individuals who take substrates of these enzymes (Brandolese et al. 2001). Finally,
the first 3 months of life represents a dramatic maturation time for the activity of
many drug metabolizing enzymes. When considered in the context of a similar
dramatic, nonlinear increase in body size (i.e., both weight and length), individuali-
zation of drug dose based on pharmacokinetic data is often a real challenge,
especially for agents where attainment of critical target plasma concentrations (or
systemic exposures) is necessary. Therefore, one can assume that there will be great
variability of exposure in studies with infants in this age group, especially when
“standard doses” of a drug are given without adjustment during the first few months
of life.
6.5 CYP2E1
CYP2E1 is being increasingly recognized for its importance in the oxidative

metabolism of a wide variety of pharmaceuticals (e.g., acetaminophen, halothane,
331(neonates/preterms)
1000 333(1-11 months)
334(1-11 yrs)
337 (12-16 yrs)
100
10
0.1
0.0 0.2 0.4 0.6 0.8 1.0 4.0 8.0 12.0 16.0
AGE (years)
Fig. 1 Aggregate apparent oral clearance (CL/F) data for pantoprazole obtained from four
pediatric clinical pharmacokinetic studies of the drug (study numbers 331, 333, 334, and 337)
performed as part of pediatric labeling studies conducted under a written request from the U.S.
Food and Drug Administration. All studies involved administration of a single oral dose of
pantoprazole given as the proprietary drug formulation. To illustrate the association of develop-
ment with pantoprazole pharmacokinetics, the value of CL/F has been normalized to a “standard”
adult weight of 70 kg
and ethanol) (Jimenez-Lopez and Cederbaum 2005). However, only in the last
5 years has the developmental pattern of this important enzyme been well under-
stood (Johnsrud et al. 2003). Nevertheless, human hepatic CYP2E1 developmental
expression is difficult to appreciate due to the multiple levels of regulation in its
activity. For example, CYP2E1 is known to be elevated in individuals who have
high levels of ethanol consumption, in individuals who are obese, and finally in
individuals who have type 2 diabetes (Caro and Cederbaum 2004). Finally, an
increasing number of genetic polymorphisms, which lead to lower CYP2E1 protein
concentration, have been demonstrated in the literature (Hanioka et al. 2003).
To date, Johnsrud et al. have published the largest study of the activity of fetal
and pediatric liver samples to determine the ontogeny of CYP2E1 (Johnsrud et al.
2003). Measurable CYP2E1 activity was demonstrated in 18 of 49 second trimester
livers and 12 of 15 third trimester samples. Moreover, measurements of mean
concentrations of CYP2E1 protein as part of total milligrams of microsomal protein
found that second trimester infants averaged 0.35 pmol/mg, third trimester
infants 6.7 pmol/mg, newborns 8.8 pmol/mg and older infants aged 30–90 days
23.8 pmol/mg, and finally children aged 90 days to 18 years 41.4 pmol/mg. Thus,
this implies a rapid maturation starting in late fetal life and continuing through early
infancy in CYP2E1 activity. It would appear that these data demonstrate that
careful attention would be required in studies of new CYP2E1 substrates in infants
under the age of 90 days.
7 Drug Excretion
The kidney is the primary organ responsible for the excretion of drugs and their
metabolites. Maturation of renal function is a dynamic process that begins early
during fetal organogenesis and is complete by early childhood (Rhodin et al. 2009;
Chen et al. 2006). The developmental increase in glomerular filtration rate (GFR)
involves active nephrogenesis, a process that begins at 9 weeks and is complete by
36 weeks of gestation, followed by postnatal changes in renal and intrarenal blood
flow. Following birth, the GFR is approximately 2–4 ml/min/kg in term neonates
and as low as 0.6–0.8 ml/min/kg in preterm neonates (Van den Anker et al. 1995a).
GFR increases rapidly during the first 2 weeks of life followed by a steady rise until
adult values are reached by 8–12 months. This increase in GFR in the first weeks of
life is mainly because of an increase in renal blood flow. Similarly, tubular
secretory pathways are immature at birth and gain adult capacity during the first
year of life.
There is a clear controversy regarding the use of serum creatinine to predict renal
function in children (Filler and Lepage 2003). Serum creatinine depends on many
factors and residual maternally derived creatinine interferes with the assay in the
first days of life in neonates (Capparelli et al. 2001). In addition, factors that have a
negative influence on the use of plasma creatinine to predict renal function are renal
tubule integrity issues and GFR values of less than 20 mL/min/1.73 m2. In these
individuals, GFR is probably overestimated. If creatinine is measured with the Jaffé
reaction ketoacids, serum bilirubin and cephalosporins interfere with the reaction
and therefore the use of an enzymatic method should be advised because of less
interference as compared to the Jaffé method (Van den Anker et al. 1995c). A more
direct approach to estimate the GFR is to use a marker that is freely permeable
across the glomerular capillary and neither secreted nor reabsorbed by the tubulus.
Markers that have been mentioned to measure the GFR are inulin, polyfructosan S,
cystatin C, 51Cr-EDTA, 125I-iothalamate, or mannitol (Filler and Lepage 2003;
Hayton 2002). A marker to estimate the active tubular secretion in children is
p-aminohippuric acid (Hayton 2002).
However, a comparison between serum creatinine with inulin clearance in
preterm infants showed a good and clinical useful correlation and supported
serum creatinine as an appropriate measure of GFR in preterm infants already on
day 3 of life (Van Den Anker et al. 1995c).
Collectively, the aforementioned changes in GFR dramatically alter the plasma

clearance of compounds with extensive renal elimination and thus provide a
major determinant for age-appropriate dose regimen selection. Pharmacokinetic
studies of drugs primarily excreted by glomerular filtration such as ceftazidime and
famotidine have demonstrated significant correlations between plasma drug clear-
ance and normal, expected maturational changes in renal function (Van den Anker
et al. 1995a; James et al. 1998). For example, tobramycin is eliminated predomi-
nantly by glomerular filtration, necessitating dosing intervals of 36–48 h in preterm
and 24 h in term newborns (De Hoog et al. 2002). Failure to account for the
ontogeny of renal function and adjust aminoglycoside dosing regimens accordingly
can result in exposure to potentially toxic serum concentrations. Also, concomitant
medications (e.g., betamethasone, indomethacin) may alter the normal pattern of
renal maturation in the neonate (Van Den Anker et al. 1994). Thus, for drugs with
extensive renal elimination, both maturational and treatment associated changes
in kidney function must be considered and used to individualize treatment regimens
in an age-appropriate fashion.
8 Other Factors Influencing the Absorption, Distribution,

Metabolism, and Excretion of Drugs in Neonates
and Young Infants
In addition to growth and development, there are several other major variables that
will influence the pharmacokinetic parameters of drugs such as inborn or acquired
diseases, environmental influences such as body cooling, and pharmacogenomics.
It is outside the scope of this chapter to provide extensive information on these
important variables but a few will be highlighted here.
Hypoxic–ischemic events are encountered regularly in sick neonates and these
events might result in a decrease in the rate and amount of drug absorption as well
as impaired renal function. There are data to show that after perinatal asphyxia the
GFR in neonates is 50% less as compared to neonates born without asphyxia,
resulting in a decreased clearance of renally cleared drugs (Van den Anker et al.
1995b). The persistence and/or closure of a patent ductus arteriosus has a major
impact on both the volume of distribution and elimination of frequently used drugs
in the newborn (Van den Anker et al. 1995d). This has been shown for drugs such as
ceftazidime where the existence of a patent ductus and or the exposure to indo-
methacin to close this ductus was associated with a decreased GFR and a larger
volume of distribution of ceftazidime, a solely renally cleared drug. In another
study investigating ibuprofen, there was a significant increase in the clearance of
ibuprofen after closure of the ductus (Van Overmeire et al. 2001). Finally, total
body cooling is a new treatment modality that is being used to improve the
neurological outcome of neonates who suffered from perinatal asphyxia. In a
study investigating the pharmacokinetics of morphine in neonates with and without

body cooling, a clinically impressive decrease in morphine clearance was seen in
neonates on body cooling (Roka et al. 2008).
9 Pharmacogenomics: Impact for Pediatric Populations
The contribution of genetic factors to explain heterogeneity of drug response in

infants and children is another important issue with the ultimate goal for better
treatment of children based on the individual genetic makeup. One of the major
tasks is to optimally adapt the choice and amount of a drug to the individual need
of a patient and, for instance, to prevent overdosing with the risk of adverse drug
reactions. Genetic variability influences almost all ADME processes including
drug absorption (e.g., via the intestinal drug transporter P-glycoprotein/ABCB1),
drug metabolism (e.g., cytochrome P450 enzymes 2C9, 2C19, 2D6), and drug
elimination, thereby resulting in alteration of pharmacokinetics and subsequently
of pharmacodynamic processes.
There is an increasing body of evidence that genetic variants in drug meta-
bolizing enzymes (e.g., CYP450 enzymes; http://www/cypalleles.ki.se/;) as well as
in drug transporters (e.g., ABCB1/P-gp, SLCO1B1/OATP1B) (Schwab et al. 2003;
Nies et al. 2008; Niemi et al. 2011) are functional relevant (e.g., loss of function
variants or gain of function polymorphisms) with in part dramatic changes in
mRNA and/or protein expression and function (Zanger et al. 2008). Genetic
variants in drug targets such as receptor molecules or intracellular structures of
signal transduction and gene regulation directly and/or indirectly may also influ-
ence drug response and tolerability in the neonate and young infant. Based on
several novel and promising genomic technologies such as high-throughput
genotyping (e.g., MaldiTof mass spectrometry), genome-wide association studies,
and next generation sequencing, pharmacogenomic knowledge will improve our
understanding of pharmacotherapy in children but will also stimulate the drug
development process for innovative agents in the future (Russo et al. 2010).
To illustrate the impact of pediatric pharmacogenomics the link between devel-
opment and genetics related to CYP2D6, one of the most studied enzymes, will be
described. Genetic variation in CYP2D6 has been the subject of several compre-
hensive reviews in recent years (Zanger et al. 2004; Stevens et al. 2008). Poor (PM),
intermediate (IM), extensive (EM), and ultrarapid (UM) metabolizer phenotypes
are observed when a population is challenged with a probe substrate. Inheritance of
two recessive loss-of-function alleles results in the “poor-metabolizer phenotype,”
which is found in about 5–10% of Caucasians and about 1–2% of Asian subjects
(see earlier). At the other end of the spectrum, the presence of CYP2D6 gene
duplication/multiplication events, which occurs at a frequency of 1–2% in
Caucasians, most often is associated with enhanced clearance of CYP2D6 sub-
strates although cases of increased toxicity due to increased formation of pharmaco-
logically active metabolites have also been reported. Recently, this was even
illustrated by a case of a breastfeeding woman with a UM phenotype, treated with

codeine for pain after delivery, who formed so much morphine out of codeine that
she intoxicated her newborn infant (Koren et al. 2006).
The ultimate utility of genomic information in the context of pharmacokinetics
is when the genotype is shown to be predictive of the phenotype; specifically, when
it can reliably predict the functional activity of a given enzyme and/or drug
transporter. This is exemplified by use of the CYP2D6 activity score, which is
derived based upon the functional impact (on CYP2D6 activity) of a given combi-
nation of CYP2D6 alleles. A potential caveat with use of the CYP2D6 activity score
resides with the fact that it has been validated in adults in whom the phenotypic
CYP2D6 activity is fully developed (Zanger et al. 2001). In other words, the
contribution of the genetic variation (e.g., CYP2D6 polymorphisms) to the pheno-
typic variability in drug disposition in adults has been explored. Very recently,
Gaedigk et al. reported the use of this activity score also in infants (Gaedigk et al.
2008), but we still have to fit this genetic variation into the age-dependent matura-
tion during infancy. At present we know that age and genetic determinants
of CYP2D6 expression constitute significant determinants of inter-individual
variability in CYP2D6-dependent metabolism during ontogeny. Very recently, it
was documented that the in vivo phenotypic CYP2D6 activity was concordant with
the genotype from 42 weeks postmenstrual age onwards (Allegaert et al. 2008;
Blake et al. 2007). This indicates that for clinicians treating neonates, young
infants, children, and adolescents the genetic variation in CYP2D6 is the major
player to consider if prescribing CYP2D6 substrates.
In summary, both genetic and environmental factors contribute to inter-
individual variability in the PK of medications metabolized by CYP2D6 (Leeder
2003; Krekels et al. 2007). In this context, a recent paper using a whole body
physiology-based pharmacokinetic (PBPK) modeling approach to investigate the
contribution of CYP2D6 genetics on codeine administration in breastfeeding
mothers and their babies supports the evidence that pediatric pharmacogenomics
comprises more than a single gene, and developmental aspects of physiological
processes need to be considered (Willmann et al. 2009).
If CYP2D6 genotyping is becoming a standard laboratory test and the CYP2D6
activity score has been validated in infants, children, and adolescents, this will
surely improve our capacity to predict the doses of CYP2D6 substrates required to
treat the neonates, young infants, children, and adolescents in a more safe and
effective way.
10 The Interface of Pharmacokinetics and Pharmacodynamics
Although, it is generally accepted that developmental differences in drug action

exist, there is little scientific evidence of real age related pharmacodynamic
variation among children of different age groups and adults. Age-related pharma-
cokinetic variation in drug clearance has the potential to alter the systemic
pH change
9
8
7
6
pH Change
5
4
3
2
1
0
0 4 8 12 16 20 24
Time (hours)
Fig. 2 Time dependent change in intragastric pH in a population of neonates administered a

single intravenous dose of famotidine. Figure adapted from James et al. (1998)
exposure of drug from given dose with the consequence of producing less or more
drug being available at the receptor(s) consequent to whether drug clearance is
decreased or increased relative to values in adults. The resultant alteration in the
dose–concentration profile may result in an attenuated (ineffective) or exagge-
rated (toxicity) pharmacodynamic response in an infant or child, a situation
which is especially relevant for drugs with a narrow therapeutic index (e.g.,
aminoglycoside antibiotics, digoxin, antiarrhythmic agents). Thus, in some
circumstances, apparent developmental differences in drug response/effect may
be simply explained on pharmacokinetic basis. This is illustrated by the H 2
antagonist famotidine where consequent to a marked reduction in plasma clear-
ance (i.e., renal elimination), a single intravenous dose produced a sustained
increase in the intragastric pH in neonates for a 24-h postdose period (Fig. 2)
(James et al. 1998).
11 Pediatric Dose Selection Based upon Pharmacokinetic

Principles
Most current age-specific dosing requirements are based on the known influence of
ontogeny on drug disposition. Current gaps in our knowledge (e.g., incomplete
developmental profiles for hepatic and extrahepatic drug metabolizing enzymes,
lack of knowledge with regard to expression of drug transporters that may influence
drug clearance and/or bioavailability) prevent the use of simple formulas and/or
allometric scaling for effective pediatric dose prediction; a fact especially true in
very young infants where the relationship between body size and the maturation of
pathways predominantly responsible for drug clearance are not linear (Holford
2010). Such approaches (e.g., allometric scaling) may have some potential clinical
utility in children older than 3 years of age and adolescents whose organ function
and body composition approximates that of young adults.
Age-specific dosing regimens for selected commonly used drugs where
developmental differences in the dose–concentration profile have been well
characterized serve to illustrate this point. For drugs whose plasma concentrations
are routinely measured clinically (e.g., aminoglycosides, digoxin, caffeine, phenyt-
oin, phenobarbital, carbamazepine, methotrexate, cyclosporine, tacrolimus,
mycophenolate mofetil), or for whom pharmacokinetic characteristics were defined
in pediatric patients during the drug development process, individualization of
treatment based on patient-derived and in selected instances, population-estimated
pharmacokinetic parameters is easily achieved. However, in the absence of such
pharmacokinetic data and/or established pediatric dosing guidelines, alternate
methods for dose selection must be used.
As discussed previously, the majority of age-adjusted pediatric drug dosing
regimens utilize either body weight or surface area as surrogates to reflect the
developmental determinants of drug disposition. Dose selection based on body
weight or body surface areas will generally produce similar plasma concentration
profiles except for those drugs whose apparent volume of distribution (Vd)
corresponds to the extracellular fluid pool (i.e., Vd < 0.3 L/kg), where a body
surface area based approach is preferable. In contrast, for drugs whose apparent
Vd exceeds the extracellular fluid space (i.e., >0.3 L/kg), a body weight based
approach for dose selection is preferable and as a result is the most frequently used
approach for dosing in pediatrics.
When the pediatric dose for a given drug is not known these principles can be
used to best approximate a proper dose for the initiation of treatment. Ritschel and
Kearns (2009) have described an approach to determine dose in infants that is
illustrated by the following equations:
Infant dose ðif Vd < 0:3 L/kgÞ ¼ ðinfant BSA in m2 =1:73 m2 Þ adult dose,
Infant dose ðif Vd 0:3 L/kgÞ ¼ ðinfant BW in kg=70 kgÞ adult dose:
This approach is only useful for selection of dose size, and does not offer
information regarding dosing interval since the equations contain no specific
variable that describes potential age-associated differences in drug clearance. It is
also important to note that this approach assumes that the body height and weight of
a given child are appropriate (i.e., normal) for age and there are no abnormalities in
body composition (e.g., edema, ascites) that can be produced by disease.
In neonates and young infants, the dosing interval for drugs with significant
(i.e., >50%) renal elimination by glomerular filtration can be approximated by
estimation of the apparent elimination half-life (t1/2) of the drug at a given point in
development by using the following equations:
kel infant ¼ kel adult f½ððGFRinfant =GFRadult Þ 1Þ Fel þ 1g;
T1=2 infant ¼ 0:693=kel infant ;
where kel represents the average terminal apparent terminal elimination rate con-
stant, GFR is an estimate of the glomerular filtration rate (which can be obtained
from either a creatinine clearance determination or age-related normal values), and
Fel is the fraction of drug excreted unchanged in the urine.
Alternatively, projection of pediatric dose requirement can be performed using
in silico techniques (e.g., whole body physiologically based pharmacokinetic/
pharmacodynamic models, population-based simulation, PK-Sim Packages, Simcyp
Pediatric ADME Simulator) (Johnson and Rostami-Hodjegan 2011). The success
of these approaches (i.e., prediction accuracy) is based upon the availability and
reliability of parameter estimates (either pharmacokinetic, pharmacodynamic, or
pharmacogenomic) and their prior knowledge in the specific subpopulation being
used for dose projection (Espie et al. 2009). These caveats are especially important
during early infancy where dynamic changes in drug disposition and action are
likely consequent to ontogeny and developmental maturity in drug clearance
pathways has not yet been attained.
12 Conclusions
The pediatric patient population consisting of neonates, infants, children, and

adolescents shows unique differences in pharmacokinetic parameters as compared
to adults and therefore requires specific dosage recommendations. While the pau-
city of pharmacokinetic and physiological data makes it difficult to precisely
determine drug doses in pediatric patients, knowledge of the effects of growth,
maturation, environmental influences, and pharmacogenetic background on absorp-
tion, distribution, metabolism, and elimination of frequently used medicines will
allow more appropriate dosing recommendations for this patient population.
Clearly, much more research is needed to fully understand the impact of develop-
ment on the disposition of a drug. As described in this chapter, studies with
substrates as markers for hepatic metabolic activity or renal function and in vitro
data are very useful for a better understanding of this impact. Finally, there is an
urgent need to better understand the metabolic activity, carrier mechanisms, and
drug transporters related to the gastrointestinal tract.
Acknowledgements Johannes van den Anker is supported in part by FP7 grants TINN (223614),
TINN2 (260908), and NEUROSIS (223060), and Matthias Schwab is supported in part by the FP7
grant NEUROSIS (223060).
References
Alcorn J, McNamara PJ (2002) Ontogeny of hepatic and renal systemic clearance pathways in
infants: part I. Clin Pharmacokinet 41:959–998
Allegaert K, Anderson BJ, Verbesselt R, Debeer A, de Hoon J, Devlieger H et al (2005) Tramadol
disposition in the very young: an attempt to assess in vivo cytochrome P-450 activity.
Br J Anaesth 95:231–239
Allegaert K, van Schaik RH, Vermeersch S, Verbesselt R, Cossey V, Vanhole C et al (2008)
Postmenstrual age and CYP2D6 polymorphisms determine tramadol O-demethylation in
critically ill neonates and infants. Pediatr Res 63:674–679
Allegaert K, Rochette A, Veyckemans F (2011) Developmental pharmacology of tramadol during
infancy: ontogeny, pharmacogenetics and elimination clearance. Paediatr Anaesth 21(3):
266–273
Anderson BJ, Holford NH (2008) Mechanism-based concepts of size and maturity in pharmacoki-
netics. Annu Rev Pharmacol Toxicol 48:303–332
Anderson BJ, van Lingen RA, Hansen TG, Lin YC, Holford NH (2002) Acetaminophen develop-
mental pharmacokinetics in premature neonates and infants: a pooled population analysis.
Anaesthesiology 96:1336–1345
Aranda JV, Collinge JM, Zinman R, Watters G (1979) Maturation of caffeine elimination in
infancy. Arch Dis Child 54:946–949
Armstrong RW, Eichner ER, Klein DE, Barthel WF, Bennett JV, Jonsson V et al (1969)
Pentachlorophenol poisoning in a nursery for newborn infants. II. Epidemiologic and toxico-
logic studies. J Pediatr 75:317–325
Bajpai M, Roskos LK, Shen DD, Levy RH (1996) Roles of cytochrome P4502C9 and cytochrome
P4502C19 in the stereoselective metabolism of phenytoin to its major metabolite. Drug Metab
Dispos 24:1401–1403
Balistreri W, Zimmer L, Suchy FJ, Bove KE (1984) Bile salt sulfotransferase: alterations during
maturation and non-inducibility during substrate ingestion. J Lipid Res 25:228–235
Bartelink IH, Rademaker CM, Schobben AF, van den Anker JN (2006) Guidelines on paediatric
dosing on the basis of developmental physiology and pharmacokinetic considerations. Clin
Blake MJ, Castro L, Leeder JS, Kearns GL (2005) Ontogeny of drug metabolizing enzymes in the
neonate. Semin Fetal Neonatal Med 10:123–128
Blake MJ, Abdel-Rahman SM, Pearce RE, Leeder JS, Kearns GL (2006) Effect of diet on the
development of drug metabolism by cytochrome P-450 enzymes in healthy infants. Pediatr Res
60:717–723
Blake MJ, Gaedigk A, Pearce RE, Bomgaars LR, Christensen ML, Stowe C et al (2007) Ontogeny
of dextromethorphan O- and N-demethylation in the first year of life. Clin Pharmacol Ther
81:510–516
Brandolese R, Scordo MG, Spina E, Gusella M, Padrini R (2001) Severe phenytoin intoxication in
a subject homozygous for CYP2C9*3. Clin Pharmacol Ther 70:391–394
Brown CM, Reisfeld B, Mayeno AN (2008) Cytochromes P450: a structure-based summary of
biotransformations using representative substrates. Drug Metab Rev 40:169–184
Capparelli EV, Lane JR, Romanowski GL, McFeely EJ, Murray W, Sousa P et al (2001) The
influences of renal function and maturation on vancomycin elimination in newborns and
infants. J Clin Pharmacol 41:927–934
Card SE, Tompkins SF, Brien JF (1989) Ontogeny of the activity of alcohol dehydrogenase and
aldehyde dehydrogenases in the liver and placenta of the guinea pig. Biochem Pharmacol
38:2535–2541
Caro AA, Cederbaum AI (2004) Oxidative stress, toxicology, and pharmacology of CYP2E1.
Annu Rev Pharmacol Toxicol 44:27–42
Chen N, Aleksa K, Woodland C, Rieder M, Koren GL (2006) Ontogeny of drug elimination by the
human kidney. Pediatr Nephrol 21:160–168
De Hoog M, Mouton JW, Schoemaker RC, Verduin CM, van den Anker JN (2002) Extended-
interval dosing of tobramycin in neonates: implications for therapeutic drug monitoring. Clin
De Hoog M, Mouton JW, van den Anker JN (2005) New dosing strategies for antibacterial agents
in the neonate. Semin Fetal Neonatal Med 10:185–194
De Wildt SN, Kearns GL, Leeder JS, van den Anker JN (1999) Glucuronidation in humans:
pharmacogenetic and developmental aspects. Clin Pharmacokinet 36:439–452
De Wildt SN, Kearns GL, Hop WC, Murry DJ, Abdel-Rahman SM, van den Anker JN (2001)
Pharmacokinetics and metabolism of intravenous midazolam in preterm infants. Clin
Edginton AN, Schmitt W, Voith B, Willmann S (2006) A mechanistic approach for the scaling of
clearance in children. Clin Pharmacokinet 45:683–704
Erenberg A, Leff RD, Haack DG, Mosdell KW, Hicks GM, Wynne BA (2000) Caffeine citrate for
the treatment of apnea of prematurity: a double-blind, placebo-controlled study. Pharmaco-
therapy 20:644–652
Espie P, Tytgat D, Sargentini-Maier ML, Poggesi I, Watelet JB (2009) Physiologically based
pharmacokinetics (PBPK). Drug Metab Rev 41:391–407
Evans NJ, Rutter N, Hadgraft J, Parr G (1985) Percutaneous administration of theophylline in the
preterm infant. J Pediatr 107:307–311
Evans WE, Relling MV, Petros WP, Meyer WH, Mirro J Jr, Crom WR (1989) Dextromethorphan
and caffeine as probes for simultaneous determination of debrisoquin-oxidation and N-acetylation
phenotypes in children. Clin Pharmacol Ther 45:568–573
Feinblatt BI, Aceto T, Beckhorn G, Bruck E (1966) Percutaneous absorption of hydrocortisone in
children. Am J Dis Child 112:218–224
Filler G, Lepage N (2003) Should the Schwartz formula for estimation of GFR be replaced by
cystatin C formula? Pediatr Nephrol 18:981–985
Friis-Hansen B (1983) Water distribution in the foetus and newborn infant. Acta Paediatr Scand
305:7–11
Gaedigk A, Simon D, Pearce RE, Bradford LD, Kennedy MJ, Leeder JS (2008) The CYP2D6
activity score: translating genotype information into a quantitative measure of phenotype. Clin
Ginsberg G, Hattis D, Miller M, Sonawane B (2004) Pediatric pharmacokinetic data: implications
for environmental risk assessment for children. Pediatrics 113:973–983
Hanioka N, Tanaka-Kagawa T, Miyata Y, Matsushima E, Makino Y, Ohno A et al (2003)
Functional characterization of three human cytochrome P450 2E1 variants with amino acid
substitutions. Xenobiotica 33:575–586
Hayton WL (2002) Maturation and growth of renal function: dosing renally cleared drugs in
children. AAPS PharmSci 2:e3
Hines RN (2008) The ontogeny of drug metabolism enzymes and implications for adverse drug
events. Pharmacol Ther 118:250–267
Hines RN, McCarver DG (2002) The ontogeny of human drug-metabolizing enzymes: phase I
oxidative enzymes. J Pharmacol Exp Ther 300:355–360
Holford N (2010) Dosing in children. Clin Pharmacol Ther 87:367–370
James LP, Marotti T, Stowe C, Farrar HC, Taylor B, Kearns GL (1998) Pharmacokinetics and
pharmacodynamics of famotidine in infants. J Clin Pharmacol 38:1089–1095
Jimenez-Lopez JM, Cederbaum AI (2005) CYP2E1-dependent oxidative stress and toxicity: role
in ethanol-induced liver injury. Expert Opin Drug Metab Toxicol 1:671–685
Johnson TN, Rostami-Hodjegan A (2011) Resurgence in the use of physiologically based phar-
macokinetic models in pediatric clinical pharmacology: parallel shift in incorporating the
knowledge of biological elements and increased applicability to drug development and clinical
practice. Paediatr Anaesth 21(3):291–301
Johnson TN, Rostami-Hodjegan A, Tucker GT (2006) Prediction of the clearance of eleven drugs
and associated variability in neonates, infants and children. Clin Pharmacokinet 45:931–956
Johnson TN, Tucker GT, Rostami-Hodjegan A (2008) Development of CYP2D6 and CYP3A4 in
the first year of life. Clin Pharmacol Ther 83:670–671
Johnsrud EK, Koukouritaki SB, Divakaran K, Brunengraber LL, Hines RN, McCarver DG
(2003) Human hepatic CYP2E1 expression during development. J Pharmacol Exp Ther
307:402–407
Jung F, Richardson TH, Raucy JL, Johnson EF (1997) Diazepam metabolism by cDNA-
expressed human 2C P450s: identification of P4502C18 and P4502C19 as low K(M) diazepam
N-demethylases. Drug Metab Dispos 25:133–139
Kearns GL (2000) Impact of developmental pharmacology on pediatric study design: overcoming
the challenges. J Allergy Clin Immunol 106:S128–S139
Kearns GL, Winter HS (2003) Proton pump inhibitors in pediatrics: relevant pharmacokinetics and
pharmacodynamics. J Pediatr Gastroenterol Nutr 37(Suppl I)):S52–S59
Kearns GL, Abdel-Rahman SM, Alander SW, Blowey DL, Leeder JS, Kauffman RE (2003a)
Developmental pharmacology – drug disposition, action, and therapy in infants and children. N
Engl J Med 349:1157–1167
Kearns GL, Robinson PK, Wilson JT, Wilson-Costello D, Knight GR, Ward RM et al (2003b)
Cisapride disposition in neonates and infants: in vivo reflection of cytochrome P450 3A4
ontogeny. Clin Pharmacol Ther 4:312–325
Kearns GL, Jungbluth GL, Abdel-Rahman SM, Hopkins NK, Welshman IR, Grzebyk RP et al
(2003c) Impact of ontogeny on linezolid disposition in neonates and infants. Clin Pharmacol
Ther 74:413–422
Kearns GL, Anderson T, James LP, Gaedigk A, Kraynak RA, Abdel-Rahman SM et al (2003d)
Omeprazole disposition in children following single dose administration. J Clin Pharmacol
43:840–848
Kerr BM, Thummel KE, Wurden CJ, Klein SM, Kroetz DL, Gonzalez FJ et al (1994) Human liver
carbamazepine metabolism. Role of CYP3A4 and CYP2C8 in 10,11-epoxide formation.
Biochem Pharmacol 47:1969–1979
Kinirons MT, O’Shea D, Kim RB, Groopman JD, Thummel KE, Wood AJ et al (1999) Failure of
erythromycin breath test to correlate with midazolam clearance as a probe of cytochrome
P4503A. Clin Pharmacol Ther 66:224–231
Klotz U (2007) The role of pharmacogenetics in the metabolism of antiepileptic drugs: pharmaco-
kinetics and therapeutic implications. Clin Pharmacokinet 46:271–279
Koren G, Cairns J, Chitayat D, Gaedigk A, Leeder JS (2006) Pharmacogenetics of morphine
poisoning in a breastfed neonate of a codeine-prescribed mother. Lancet 368:704
Koukouritaki SB, Manro JR, Marsh SA, Stevens JC, Rettie AE, McCarver DG et al (2004)
Developmental expression of human hepatic CYP2C9 and CYP2C19. J Pharmacol Exp Ther
308:965–974
Kraus DM, Fischer JH, Reitz SJ, Kecskes SA, Yeh TF, McCulloch KM et al (1993) Alterations in
theophylline metabolism during the first year of life. Clin Pharmacol Ther 54:351–359
Krekels EH, van den Anker JN, Baiardi P, Cella M, Cheng KY, Gibb DM et al (2007) Pharmaco-
genetics and paediatric drug development: issues and consequences to labelling and dosing
recommendations. Expert Opin Pharmacother 8:1787–1799
Lambert GH, Schoeller DA, Kotake AN, Flores C, Hay D (1986) The effect of age, gender, and
sexual maturation on the caffeine breath test. Dev Pharmacol Ther 9:375–388
Lee CR, Goldstein JA, Pieper JA (2002) Cytochrome P450 2C9 polymorphisms: a comprehensive
review of the in vitro and human data. Pharmacogenetics 12:251–263
Leeder JS (2003) Developmental and pediatric pharmacogenomics. Pharmacogenomics
4:331–341
Leeder JS, Kearns GL, Spielberg SP, van den Anker JN (2010) Understanding the relative roles of
pharmacogenetics and ontogeny in pediatric drug development and regulatory science. J Clin
Pharmacol 50(12):1377–1387
Loughnan PM, Greenwald A, Purton WW, Aranda JV, Watters G, Neims AH (1977) Pharmaco-
kinetic observations of phenytoin disposition in the newborn and young infant. Arch Dis Child
52:302–309
McCarver DG, Hines RN (2002) The ontogeny of human drug metabolizing enzymes: phase II
conjugation enzymes and regulatory mechanisms. J Pharmacol Exp Ther 300:361–366
Milavetz G, Vaughan LM, Weinberger MM, Hendeles L (1986) Evaluation of a scheme for
establishing and maintaining dosage of theophylline in ambulatory patients with chronic
asthma. J Pediatr 109:351–354
Nachman RL, Esterly NB (1980) Increased skin permeability in preterm infants. J Pediatr
96:99–103
Nelson DR, Koymans L, Kamataki T, Stegeman JJ, Feyereisen R, Waxman DJ et al (1996) P450
superfamily: update on new sequences, gene mapping, accession numbers and nomenclature.
Pharmacogenetics 6:1–42
Niemi M, Pasanen MK, Neuvonen PJ (2011) Organic anion transporting polypeptide1B1: a
genetically polymorphic transporter of major importance for hepatic drug uptake. Pharmacol
Rev 63(1):157–181
Nies AT, Schwab M, Keppler D (2008) Interplay of conjugating enzymes with OATP uptake
transporters and ABCC/MRP efflux pumps in the elimination of drugs. Expert Opin Drug
Metab Toxicol 4:545–568
Payne K, Mattheyse FJ, Liedenberg D, Dawes T (1989) The pharmacokinetics of midazolam in
paediatric patients. Eur J Clin Pharmacol 37:267–272
Pynn€onen S, Sillanp€aa M, Frey H, Iisalo E (1977) Carbamazepine and its 10,11-epoxide in
children and adults with epilepsy. Eur J Clin Pharmacol 11:129–133
Radde IC, McKercher HG (1985) Transport through membranes and development of membrane
transport. In: MacLeod SM, Radde IC (eds) Textbook of pediatric clinical pharmacology. PSG,
Littleton, MA, pp 1–16
Rane A, Bertilsson L, Palmer L (1975) Disposition of placentally transferred carbamazepine
(Tegretol) in the newborn. Eur J Clin Pharmacol 8:283–284
Rhodin MM, Anderson BJ, Peters AM, Coulthard MG, Wilkins B, Cole M et al (2009) Human
renal function maturation: a quantitative description using weight and postmenstrual age.
Pediatr Nephrol 24:67–76
Ritschel WA, Kearns GL (eds) (2009) Handbook of basic pharmacokinetics, 7th edn. American
Pharmacists Association, Washington, DC, pp 274–276
Riva R, Contin M, Albani F, Perucca E, Procaccianti G, Baruzzi A (1985) Free concentration of
carbamazepine and carbamazepine-10,11-epoxide in children and adults. Influence of age and
phenobarbitone co-medication. Clin Pharmacokinet 10:524–531
Roka A, Melinda KT, Vasarhelyi B, Machay T, Azzopardi D, Szabo M (2008) Elevated morphine
concentrations in neonates treated with morphine and prolonged hypothermia for hypoxic
ischemic encephalopathy. Pediatrics 121:e844–e849
Russo R, Capasso M, Paolucci P, Iolascon A, TEDDY European Network of Excellence (2010)
Pediatric pharmacogenetic and pharmacogenomic studies: the current state and future
perspectives. Eur J Clin Pharmacol ePub 2011;67 suppl 1:17–27 Epub 2010 Nov 11
Schwab M, Eichelbaum M, Fromm MF (2003) Genetic polymorphisms of the human MDR1 drug
transporter. Annu Rev Pharmacol Toxicol 43:285–307
Stevens JC, Hines RN, Gu C, Koukouritaki SB, Manro JR, Tandler PJ et al (2003) Developmental
expression of the major human hepatic CYP3A enzymes. J Pharmacol Exp Ther 307:573–582
Stevens JC, Marsh SA, Zaya MJ, Regina KJ, Divakaran K, Le M et al (2008) Developmental
changes in human liver CYP2D6 expression. Drug Metab Dispos 36:1587–1593
Strolin Benedetti M, Baltes EL (2003) Drug metabolism and disposition in children. Fundam Clin
Pharmacol 17:281–299
Suzuki Y, Mimaki T, Cox S, Koepke J, Hayes J, Walson PD (1994) Phenytoin age-dose-
concentration relationship in children. Ther Drug Monitor 16(2):145–150
Tateishi T, Asoh M, Yamaguchi A, Yoda T, Okano YJ, Koitabashi Y (1999) Developmental

changes in urinary elimination of theophylline and its metabolites in pediatric patients. Pediatr
Res 45:66–70
Treluyer JM, Jacqz-Aigrain E, Alvarez F, Cresteil T (1991) Expression of CYP2D6 in developing
human liver. Eur J Biochem 202:583–588
Van den Anker JN, Rakhmanina NY (2006) Pharmacological research in pediatrics: from neonates
to adolescents. Adv Drug Deliv Rev 58:4–14
Van den Anker JN, Hop W, de Groot R, van der Heijden AJ, Broerse HM, Lindemans J et al (1994)
Effects of prenatal exposure to betamethasone and indomethacin on the glomerular filtration
rate in the preterm infant. Pediatr Res 36:578–581
Van den Anker JN, Schoemaker R, Hop W, van der Heijden BJ, Weber A, Sauer PJ et al (1995a)
Ceftazidime pharmacokinetics in preterm infants: effects of renal function and gestational age.
Clin Pharmacol Ther 58:650–659
Van den Anker JN, Van der Heijden AJ, Hop WCJ, Schoemaker RC, Broerse HM, Neijens HJ et al
(1995b) The effect of asphyxia on the pharmacokinetics of ceftazidime in the term newborn.
Pediatr Res 38:808–811
Van den Anker JN, de Groot R, Broerse HM, Sauer PJ, van der Heijden BJ, Neijens HJ et al
(1995c) Assessment of glomerular filtration rate in preterm infants by serum creatinine:
comparison with inulin clearance. Pediatrics 96:1156–1158
Van den Anker JN, Hop WCJ, Schoemaker RC, Van der Heijden AJ, Neijens HJ, De Groot R
(1995d) Ceftazidime pharmacokinetics in preterm infants: effects of postnatal age and postna-
tal exposure to indomethacin. Br J Clin Pharmacol 40:439–443
Van Overmeire B, Touw D, Schepens PJC, Kearns GL, van den Anker JN (2001) Ibuprofen
pharmacokinetics in preterm infants with patent ductus arteriosus. Clin Pharmacol Ther
70:336–343
Willmann S, Edgington AN, Coboeken K, Ahr G, Lippert J (2009) Risk to the breast-fed neonate
from codeine treatment to the mother: a quantitative mechanistic modelling study. Clin
Zanger UM, Fischer J, Raimundo S, Stuven T, Evert BO, Schwab M, Eichelbaum M (2001)
Comprehensive analysis of the genetic factors determining expression and function of hepatic
CYP2D6. Pharmacogenetics 11:573–585
Zanger UM, Raimundo S, Eichelbaum M (2004) Cytochrome P450 2D6: overview and update on
pharmacology, genetics and biochemistry. Naunyn-Schmiedebergs Arch Pharmacol
369:23–37
Zanger UM, Turpeinen M, Klein K, Schwab M (2008) Functional pharmacogenetics/genomics
of human cytochromes P450 involved in drug biotransformation. Anal Bioanal Chem
392:1093–1108
Principles of Therapeutic Drug Monitoring
Wei Zhao and Evelyne Jacqz-Aigrain
Contents
1 Therapeutic Drug Monitoring: Definition, Which Drug to Measure? . . . . . . . . . . . . . . . . . . . . . . 78
2 Pharmacological Differences Between Adults and Children . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78
3 TDM in Practice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
3.1 Timing of Sampling for TDM in Children (Table 2) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80
3.2 Technical Aspects of TDM: Sample Collection, Analytical Methods . . . . . . . . . . . . . . . 81
3.3 Which Samples to Analyze: Blood or Saliva, Dried Blood Spot? . . . . . . . . . . . . . . . . . . . 82
4 New Approaches for TDM: Population Pharmacokinetics and Bayesian Estimator . . . . . . 84
4.1 Bayesian Estimation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 84
5 Pharmacodynamic Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 87
Abstract Therapeutic drug monitoring (TDM) is central to optimize drug efficacy

in children, because the pharmacokinetics and pharmacodynamics of most drugs
differ greatly between children and adults. Many factors should be analyzed to
implement TDM in the pediatric population, including a validated pharmacological
parameter and an analytical method adapted to children as limited sampling volumes
and high sensitivity are required. The use of population approaches, new analytical
methods such as saliva and dried blood spots, and pharmacodynamic monitoring
give attractive options to improve TDM, individualize therapy in order to optimize
efficacy and reduce adverse drug reactions.
Keywords Monitoring • Concentration • Therapeutic index • Pharmacokinetics •

Pharmacodynamics • Bayesian estimation
W. Zhao • E. Jacqz-Aigrain (*)

Department of Pediatric Pharmacology and Pharmacogenetics, Clinical Investigation Center, CIC
Inserm 9202, French network of Pediatric Investigation Centers (CICPaed), Hôpital Robert Debré,
48 Boulevard Sérurier, 75935 Paris, France
e-mail: evelyne.jacqz-aigrain@rdb.aphp.fr

78 W. Zhao and E. Jacqz-Aigrain
1 Therapeutic Drug Monitoring: Definition, Which Drug

to Measure?
TDM is used, in combination with parameters of the patient’s clinical condition to

help guide decisions regarding drug dosing in individual patients (Walson 1998) in
order to optimize therapeutic efficacy and minimize adverse events. The general
requirements for a drug to be considered for TDM are presented in Table 1.
2 Pharmacological Differences Between Adults and Children
Although criteria for TDM pertain to both adults and children, children are
more likely to benefit from TDM, as in contrast to the adult situation, validated
dosage recommendations are limited for many drugs prescribed in children.
Indeed, approximately 70% of drugs prescribed to children, and more than 93%
to critically ill neonates, are unlicensed or used in an off-label manner (‘t Jong
et al. 2000, 2002; Conroy et al. 2000). As growth and development are a contin-
uum, with continuous changes in physiological parameters during childhood,
marked differences in the pharmacokinetic and pharmacodynamic behavior of
many drugs are reported between children and adults. All pharmacokinetic phases
are involved (Kearns et al. 2003): in such situations, pediatric dosage is empirical.
As a result, therapeutic failures, adverse events, and even fatalities may occur
(Ince et al. 2009).
Oral absorption may be altered by changes in gastroenterological physiology
with age. During the neonatal period, intragastric pH is relatively high (greater than
4), as both basal acid output and the total volume of gastric secretions are limited.
As a consequence, the bioavailability of acid labile compounds is increased
Table 1 Requirements to set up TDM for a given drug (Touw et al. 2005; Soldin and Soldin 2002)
• A relationship exists between drug plasma (blood) concentration and effect and is stronger than
between drug dosage and effect
• The drug has a narrow therapeutic index, i.e., small difference between the therapeutic and toxic
concentrations, between the low concentration, without effect and the high concentration,
associated with toxicity
• The concentrations resulting from a given dose are unpredictable as a result of inter- and
intra-individual variability
• The clinical effects are not easily measurable
• A rapid and reliable analytical method is validated to determine drug and metabolites
concentrations
In addition, TDM can also be useful:
• If toxicity is suspected
• In the absence of drug response when subtherapeutic concentrations are suspected or compliance
is questionable
• When dose adjustment is required as a result of drug interactions or changes in clinical state
Principles of Therapeutic Drug Monitoring 79
compared to older children (Agunod et al. 1969; Rodbro et al. 1967). Furthermore,
in infants younger than 6 months, gastric emptying is much slower, which probably
prolongs the time required to achieve maximal plasma levels. Most of these
physiological variables affecting oral absorption are immature, reaching adult
values, between 5 and 10 years of age. Percutaneous absorption is enhanced in
infants, which may be partly accounted by the presence of a thinner stratum
corneum in the preterm neonate (Rutter 1987) and by the relatively greater extent
of cutaneous perfusion and hydration of the epidermis throughout childhood (Okah
et al. 1995; Fluhr et al. 2000). Rectal absorption may also be enhanced in neonates
and infants (Kearns et al. 2003). Intramuscular absorption depends on several
physiological factors: reduced skeletal-muscle blood flow and inefficient muscular
contractions may reduce the rate of intramuscular drug absorption. On the other
hand, the relatively higher density of skeletal-muscle capillaries in infants may
increase absorption (Greenblatt and Koch-Weser 1976; Carry et al. 1986).
Distribution may be altered by the differences in body composition. In
neonates and infants, the relatively larger total body water (70–75% in neonates
versus 50–55% in adults) and extracellular water component (40% in neonates
versus 20% in adults) and lower fat tissue (15% in infants versus 20% in adults)
affect the distribution of drugs which are mainly distributed in body water and to a
lesser extent of lipophilic drugs (Koren 1997). In addition, the lower protein
binding in neonates and infant increases the free fraction of drugs highly bound
in older children and adults.
Metabolism is influenced by numerous factors and primarily by age. In the
neonate, the hepatic microsomal enzyme system is immature. Drug-metabolizing
activities by cytochrome P450 oxidases (CYP, phase I enzymes) and conjugating
enzymes (phase II enzymes) are substantially lower and vary extensively between
patients (See Chapter: Pharmacokinetics and maturation/development). This
explains why the variability of pharmacokinetic parameters such as clearance or
elimination half-life is much higher in children than in adults. TDM is therefore
very useful during this period, because of the lack of validated dosage regimens and
the rapid change of enzyme activities.
Renal elimination. The glomerular filtration rate (GFR) is much lower in
neonates than in older infants, children, or adults. GFR matures during infancy
and approaches an adult rate by 6–12 months postnatal age. The maturation process
of renal structure and function includes prolongation and maturation of renal
tubules, increase in renal blood flow, and improvement of filtration efficiency. In
addition, blood flow is shifted from the deeper to the more superficial nephrons
(Koren 1997).
Pharmacodynamic differences also exist between the pediatric and adult
populations. Indeed, children do not always respond to drug treatment similarly
to adults. One of the examples is warfarin. Developmental changes in the phar-
macokinetics and pharmacodynamics of warfarin enantiomers were studied in
prepubertal, pubertal, and adult patients given long-term warfarin therapy.
The results showed that the patients from these three age groups had comparable
mean plasma concentrations of unbound warfarin enantiomers. However, the
prepubertal patients showed significantly lower plasma concentrations of protein

C and prothrombin fragments 1 + 2 and greater international normalized ratio
(INR ratio between the coagulation time of a sample of blood and the normal
coagulation time, when coagulation takes place in certain standardized
conditions) and dose normalized INR than the adults. This increased response
to warfarin should be taken into account when starting treating children with
warfarin (Takahashi et al. 2000).
3 TDM in Practice
3.1 Timing of Sampling for TDM in Children (Table 2)
Drugs are usually administered at repeated doses with a constant dosage interval,
either orally or intravenously. Blood or plasma concentrations rise and fall in each
inter-dose interval, from peak to trough. For drugs with linear elimination given at
a fixed dosage regimen, drug concentrations reach steady-state conditions after
4–5 half-lives. Approximated steady-state concentrations may be reached earlier if
a loading dose is given. This estimation does not apply to drugs with saturable
elimination when given at the usual dose, i.e., phenytoin and theophylline. In such
cases of dose dependant kinetics, the drug concentrations increase disproportion-
ately. During continuous infusion, no fluctuations are expected in blood/plasma
concentrations at steady state. In some situations, drugs should be monitored before
steady-state levels are reached to ensure the efficacy and avoid toxicity (1) when the
half-live is long, in order to detect overdosing before steady state; (2) in individuals
with impaired metabolism or renal clearance; and (3) in case of potential drug
interactions. In all cases, detailed information on patient’s disease and clinical
conditions, biological parameters of interest, drug, dosage regimen and associated
therapies, and time of sampling relative to the time of drug administration are
essential to interpret the results (Gross 2001).
Table 2 Technical aspects of Delay between start of treatment and time of sampling
TDM; sample collection,
Sampling time (peak or trough?)
analytical methods
Number of samples
Conditions of sampling
Type of sample (blood, plasma, saliva, dried spot, etc.)
Volume of each sample
Appropriate collecting tube
Validated analytical method
3.2 Technical Aspects of TDM: Sample Collection, Analytical

Methods
The influence of the blood collecting tube on the concentrations measured should be
taken into consideration. Indeed, several studies have reported that inappropriate
tubes containing serum separator gels can significantly affect the determination of
phenytoin (Dasgupta et al. 1994; Quattrocchi et al. 1983) or ribavirin, the latter
being more stable in gel-containing tubes than in dry or ethylenediaminetetra-acetic
acid tubes (Marquet et al. 2010). Therefore, it is strongly recommended to evaluate
the matrix effect of blood collecting tubes when validating a new analytic method
for TDM. Another important issue in pediatric TDM is for techniques validated for
very small sample volumes, especially in neonates, with low total blood volume
(40 mL for a preterm infant of 500 g). Moreover, as hematocrit is higher in young
infants, more blood has to be drawn to obtain a similar volume of plasma. To
optimize TDM, a TDM laboratory has to develop analytical methods adapted to
the age of the patients, particularly for neonates. In addition, all laboratories should
make analytical procedures available to clinicians that include for each drug the
optimal sampling time and sampling volume required, the type of blood collecting
tubes, clinical and biological parameters required to interpret the measured concen-
tration (Koren 1997). Differences between analytical methods may have a major
impact on the results. Monitoring of immunosuppressants is taken here as an
example. Because of their high inter- and intra-individual variability and narrow
therapeutic index, TDM of immunosuppressants is mandatory both in children and
in adults whatever the indication, but primarily to prevent transplant rejection and
toxicity in organ transplanted children. Immunoassay techniques are widely used for
TDM as they are easy to perform and are less time consuming than chromatographic
methods. However, although often regarded as “specific” for the parent drug, the
antibody may cross-react with other compounds, including metabolites of the drug.
Therefore, the concentrations are often overestimated as compared with chro-
matographic assays. Due to the cross reactivity of mycophenolic acid (MPA) with
its acyl-glucuronide metabolite (AcMPAG) in enzyme-multiplied immunoassay
technique (EMIT), the concentrations of MPA determined by EMIT were systemat-
ically higher than by high-performance liquid chromatography with ultraviolet
(HPLC-UV) method, with an average positive bias of 15% in pediatric transplant
recipients (Irtan et al. 2008). In general, these differences do not affect significantly
the clinical value of TDM, although they have an impact on the target concentration
and contribute to the variability of drug concentrations reported in the literature.
However, in defined clinical conditions where the concentrations of metabolites
contribute significantly to the measured drug concentration, the differences between
analytical assays should be taken into account to interpret the results. This is the
case, for example, in liver transplanted patients immediately posttransplant receiving
mycophenolate mofetil (MMF) the prodrug of MPA, where overestimation of MPA
concentration may occur and be misleading (Sch€ utz et al. 1998).
3.3 Which Samples to Analyze: Blood or Saliva, Dried Blood

Spot?
TDM is usually performed in blood/plasma after venous sampling. Children, and

primarily younger ones, usually fear needles and injections and alternative sam-
pling techniques will satisfy both children and their parents.
Saliva sampling is an alternative procedure both noninvasive and painless. When
compared to venous blood sampling, saliva sampling has the following advantages:
(1) Sample collection with minimal patient discomfort. (2) Repeated samples easier
to obtain and very useful in patients receiving chronic treatments. Saliva sampling
has shown great interest for the TDM of anticonvulsant drugs as numerous studies
have shown a good correlation between saliva and blood concentrations of car-
bamazepine, phenytoin, primidone, and ethosuximide (Herkes and Eadie 1990;
Gorodischer et al. 1997; Liu and Delgado 1999). However, although saliva sampling
has gained adequate acceptance in pharmacokinetic and pharmacodynamic research
studies, its use in clinical practice remains limited (Drobitch and Svensson 1992).
Limiting factors are linked to saliva collection and sample analysis and include
salivary flow rate and pH, sampling conditions, contamination and protein binding
have been shown to influence drug measurements. This is the case for valproic acid
and some controversy exists for phenobarbital. Therefore, a standardized and well-
controlled sampling procedure should be developed and validated to standardize the
drug TDM in saliva (Liu and Delgado 1999; Mullangi et al. 2009)
The dried blood spot (DBS) sampling is another option for TDM in children. In
DBS sampling, blood is obtained via a finger or heel prick with an automatic lancet
and the drop of blood is collected on a sampling paper, then dried and easily kept and/
or sent for analysis. DBS offers a number of advantages over conventional venous
blood sampling, as (1) it is less invasive, avoiding classical venous puncture or
canula, (2) it requires smaller blood volume (less than 100 mL), (3) storage is simpler
and transfer is easier at room temperature, (4) DBS can be easily collected by the
patient itself or his guardian with minimum training and sent by mail to the assigned
laboratory, so that TDM results are available when patients visit the physician (Li and
Tse 2010; Edelbroek et al. 2009). DBS is increasingly used for the TDM of a wide
spectrum of drugs such as antiretroviral drugs (Koal et al. 2005; ter Heine et al.
2009a, b), immunosuppressants (Cheung et al. 2008; Hoogtanders et al. 2007;
Wilhelm et al. 2009; van der Heijden et al. 2009), and antiepileptics (la Marca
et al. 2008, 2009). The most important physiological factor that affects DBS results
is hematocrit. Hematocrit affects blood viscosity and flux and impacts diffusion
properties of blood applied on the filter paper. When hematocrit is high, diffusion
in the paper is poor, a higher volume per punch is required for analysis and a higher
concentration will be measured than when the hematocrit is low (Adam et al. 2000;
Mei et al. 2001). This should be taken into account in pediatric patients as the
hematocrit value varies with age, e.g., 0.28–0.67 in patients from birth to 1 year
and 0.35–0.42 for children (2–12 years old) (Li and Tse 2010). In addition, assay
sensitivity and specificity remain a challenge as blood volume is lower and analytical
interferences may occur. Indeed HPLC coupled with either UV or fluorescence
detection may not be suitable, the reference method being HPLC coupled with
tandem mass spectrometry (MS/MS) used in most publications on DBS analysis.
The interpretation of drug concentrations measured during monitoring should
take into account all the aspect and conditions of monitoring (including dose and
dosage schedule, the type of biological sample, analytical technique used, start of
treatment, potential drug interactions, etc.) and use reference concentrations to
draw recommendations for dosage adaptation (Table 3).
Table 3 Therapeutic concentrations for different classes of drug

Class Medication Sampling time Therapeutic range Reference
in children
Antiepileptic drugs Carbamazepine Predose 4–12 mg/mL Scheyer and Cramer
(1990)
Phenobarbital Any time during 20–60 mg/mL Warner et al. (1998)
dosage interval
after steady state
Phenytoin Predose (oral dose); Infant: 6–11 mg/mL; Free Warner et al. (1998)
1–4 h post-IV drug: 1–2 mg/mL
loading dose. At
least 2 h post-IV
dose
Primidone Predose 5–12 mg/mL Warner et al. (1998)
Valproic acid Predose 50–120 mg/mL Warner et al. (1998)
Aminoglycosides Gentamicin Predose 0.5–1 mg/mL Touw et al. (2009)
Peak 10–12 mg/mL
Tobramycin Predose 0.5–1 mg/mL Touw et al. (2009)
Peak 10–12 mg/mL
Amikacin Peak 24–35 mg/mL Sherwin et al. (2009)
AUC24h 130–590 mg h/mL
Glycopeptides Vancomycin Predose 5–10 mg/mL de Hoog et al. (2004)
Peak 20–40 mg/mL
Immunosuppressants Cyclosporine Predose Initial posttransplantation Brodehl (1994)
period: 150–250 mg/L
(kidney, liver)
Maintenance period:
100–150 mg/L
(kidney);
130–200 mg/L (liver)
2-h post oral dose Initial posttransplantation
period:
1,300–1,800 mg/L
(kidney);
800–1,200 mg/L
(liver)
Tacrolimus Predose Initial posttransplantation del Mar Fernández
period: 10–20 ng/mL De Gatta et al.
(2002)
Maintenance period:
5–15 ng/mL
MPA (after AUC12h 30–60 mg h/L del Mar Fernández
administration of De Gatta et al.
mycophenolate (2002)
mofetil – MMF)
Miscellaneous Theophylline Predose 5–15 mg/L Self et al. (1993)
Digoxin At least 6-h post dose 0.8–2 ng/mL Steinberg and
Notterman
(1994)
4 New Approaches for TDM: Population Pharmacokinetics

and Bayesian Estimator
Monitoring aims at measuring individual drug exposure based on validated phar-

macokinetic parameters that better reflect drug effect than drug dosage. Drug
monitoring may be based on different parameters: trough concentration (just before
the following administration), peak concentration, or area under the curve (AUC)
measured at steady state. Optimal interpretation of the result requires a validated
therapeutic range: the lowest limit is the concentration that produces half of the
maximum possible therapeutic effect while the upper limit is determined by toxicity
and is the concentration at which toxicity will develop but only in a limited number
of patients. A major limitation of TDM in children is that for many medications,
target concentrations are not defined in children but only based on data obtained
in adults.
“Population pharmacokinetic approaches” opened new ways for TDM. For
population pharmacokinetic modeling, numerous drug concentrations, so-called
observations, are obtained from a large number of patients, representing the entire
population. The “nonlinear mixed effects modeling is based on the simultaneous
analysis of all data obtained and Parametric method” means that the distribution of
the pharmacokinetic parameters is assumed to be normal or log-normal. Both the
interindividual and intraindividual pharmacokinetic variabilities are estimated
separately. Covariate analysis is then performed, in which demographic and
pathophysiologic (e.g., weight, age, liver and kidney function, disease severity
and genetics, etc.) predictors of variability are identified. If these predictors are
associated with clinically significant shifts in the therapeutic index, they may serve
for the design of individualized dosage regimens. The population approach allows
the analysis of either sparse and rich data, but also unbalanced data or a combina-
tion of data from experimental settings and clinical practice (Ince et al. 2009; Zhao
et al. 2009, 2010).
4.1 Bayesian Estimation
The most useful TDM application of population pharmacokinetics is dose individ-

ualization using a posteriori method – Bayesian estimation (also called “maximum
a posteriori Bayesian estimation”). It relies upon the following formula:
p(P=CÞ ¼ K p(C=PÞ p(PÞ
stating that the posterior probability density p(P/C) of the pharmacokinetic param-
eter P, given the measured concentration C in a given patient, is proportional to the
product of the likelihood of the data p(C/P) with the prior probability density of the
parameters p(P) in the population to which the patient belongs. The likelihood
depends on the pharmacokinetic model that describes the expected concentration

for a given set of parameters and covariate values, and on the residual error model,
which describes the deviation between the expected concentrations and the
measured concentrations (Tod et al. 2001).
Bayesian estimation offers more flexibility in blood sampling times, owing to its
precision and to the amount of information provided. Unlike the other a posteriori
methods, Bayesian estimation is based on population pharmacokinetic studies and
takes into account the pharmacokinetic characteristics of a typical population,
individual patient’s data including drug concentrations and covariates, but also
takes into account the variability of the pharmacokinetics parameters in the popu-
lation. In practice, the population pharmacokinetic parameters can be obtained from
the index dataset, which is used a priori to determine the distribution of pharmaco-
kinetic parameters in a given population or from the literature. In the last case, the
external validation is mandatory, as numerous factors, such as age, weight, clinical
condition, genetics, etc., can modify the population pharmacokinetic parameters. It
should be demonstrated that the published model could correctly predict the
concentrations in validation dataset.
An important issue is the validation of Bayesian estimation, either internal or
external. When the number of patients receiving the drug is limited, internal
validation using a circular permutation method can be considered. The full dataset
is randomly divided into four subsets, each one containing 25% of data and the
building group includes only part of the total data. The population parameters
obtained in each combination of three subsets using 75% of data each time,
corresponding to the building group are used to calculate the individual pharmaco-
kinetic parameters of the remaining 25% of data defined as the internal validation
group. This procedure is repeated four times (as there are four different combi-
nations of 75 and 25% datasets). Predicted concentrations or AUCs using Bayesian
estimation from four times of circular permutation are then compared with the
corresponding observed values.
The methodology of external validation is used when a large number of patients
are available, allowing the validation group to be different from the building group
and not used to define the pharmacokinetic parameters. In this situation, the patients
are randomly divided prior to any analysis, into the building vs. validation group.
The population parameters obtained in the building group are used to calculate the
individual data in the validation group, where individual predicted concentrations
or AUCs using Bayesian estimation will be compared with the observed, measured
values.
Whatever the processes of validation, according to the method described by
Sheiner and Beal (1981), the criteria for evaluating the predictive performance of
Bayesian estimation include the prediction bias prediction error (PE) and absolute
prediction error (APE). They are calculated by using the following equations:
PE ¼ ðpredicted value reference valueÞ=reference value and
APE ¼ ABS ðpredicted value reference valueÞ=reference value:

PE and APE are expressed in the results as a percentage.

The lower the PE and APE, the more accurate and precise the prediction of
Bayesian estimation are (Sheiner and Beal 1981).
Bayesian estimation have been increasingly employed in AUC-guided TDM
(e.g., cyclosporine, Mycophenolate Mofetil, carboplatin) (Irtan et al. 2007; Payen
et al. 2005; Peng et al. 1995) as well as in routine monitoring of drugs characterized
by a very high interindividual pharmacokinetic variability such as methotrexate,
tobramycin, gentamicin, etc. (Tod et al. 2001; Plard et al. 2007).
5 Pharmacodynamic Monitoring
The current TDM approach determines drug concentrations (or other pharmacoki-
netic parameters) in extracellular or whole blood fractions. It is used as a surrogate
marker of effect, but in some cases it may be hampered by the absence of correla-
tion between exposure and effect. In recent years, it was shown that the assessment
of pharmacodynamic effects provides a mean to improve and individualize drug
therapy. Numerous attempts have been made to develop biomarkers that would
complete TDM, e.g., pharmacodynamic monitoring of immunosuppressive ther-
apy, which is considered as a new strategy to tailor immunosuppressive therapy
(Oellerich et al. 2006; Sommerer et al. 2009).
However, immunosuppressive effect is complex and involves drug-independent
mediators, such as immunophilins for activity of cyclosporine and tacrolimus
(calcineurin inhibitors, CNI). Concentrations based TDM is limited in its ability
to measure drug effectiveness at its immunosuppressive site of action. As a result,
measured concentrations within the therapeutic range do not guarantee absence of
rejection or avoidance of toxicity in all patients and at all times. Pharmacodynamic
approaches are designed to address this issue (van Rossum et al. 2010). Numerous
tools have been developed for pharmacodynamic monitoring of CNI therapy, such
as calcineurin inhibition, IL-2 production, expression of genes encoding cytokines,
intra-lymphocyte ATP concentrations in CD4+ cells, and T-cell cytometric and
functional assays as markers of the degree of CNI-induced immunosuppression (de
Jonge et al. 2009). Preliminary reports also show associations between the different
pharmacodynamic markers and outcome as well as CNI pharmacokinetics (Fukudo
et al. 2005; Sanquer et al. 2004; Brunet et al. 2007). However, the routinely clinical
use of these pharmacodynamic markets remains to be validated in order to be
implemented in clinical practice. Studies in larger patient populations are needed
to evaluate the clinical value of these promising approaches.
Pharmacodynamic monitoring is not supposed to replace current concentrations
based TDM rather a complementary combination of TDM and pharmacodynamic
monitoring, which could help to improve pharmacotherapy for more effective and
safe results in individual patients.
References
Adam BW, Alexander JR, Smith SJ, Chace DH, Loeber JG, Elvers LH, Hannon WH (2000)
Recoveries of phenylalanine from two sets of dried blood spot reference materials: prediction
from hematocrit, spot volume, and paper matrix. Clin Chem 46:126–128
Agunod M, Yamaguchi N, Lopez R, Luhby AL, Glass GB (1969) Correlative study of
hydrochloric acid, pepsin, and intrinsic factor secretion in newborns and infants. Am J Dig
Dis 14:400–414
Brodehl J (1994) Consensus statements on the optimal use of cyclosporine in pediatric patients.
Transplant Proc 26:2759–2762
Brunet M, Crespo M, Millan O et al (2007) Pharmacokinetics and pharmacodynamics in renal
transplant recipients under treatment with cyclosporine and myfortic. Transplant Proc
39:2160–2162
Carry MR, Ringel SP, Starcevich JM (1986) Distribution of capillaries in normal and diseased
human skeletal muscle. Muscle Nerve 9:445–454
Cheung CY, van der Heijden J, Hoogtanders K, Christiaans M, Liu YL, Chan YH, Choi KS,
van de Plas A, Shek CC, Chau KF, Li CS, van Hooff J, Stolk L (2008) Dried blood spot
measurement: application in tacrolimus monitoring using limited sampling strategy and
abbreviated AUC estimation. Transpl Int 21:140–145
Conroy S et al (2000) Survey of unlicensed and off label drug use in paediatric wards in European
countries. European Network for Drug Investigation in Children. BMJ 320:79–82
Dasgupta A, Dean R, Saldana S, Konnaman G, McLawhon RW (1994) Absorption of therapeutic
drugs by barrier gels in serum separator blood collection tubes. Am J Clin Pathol 101:456–461
de Hoog M, Mouton JW, van den Anker JN (2004) Vancomycin: pharmacokinetics and adminis-
tration regimens in neonates. Clin Pharmacokinet 43:417–440
de Jonge H, Naesens M, Kuypers DR (2009) New insights into the pharmacokinetics and pharma-
codynamics of the calcineurin inhibitors and mycophenolic acid: possible consequences for
therapeutic drug monitoring in solid organ transplantation. Ther Drug Monit 31:416–435
del Mar Fernández De Gatta M, Santos-Buelga D, Domı́nguez-Gil A et al (2002) Immunosup-
pressive therapy for paediatric transplant patients: pharmacokinetic considerations. Clin
Drobitch RK, Svensson CK (1992) Therapeutic drug monitoring in saliva: an update. Clin
Edelbroek PM, van der Heijden J, Stolk LM (2009) Dried blood spot methods in therapeutic drug
monitoring: methods, assays, and pitfalls. Ther Drug Monit 31:327–336
Fluhr JW, Pfisterer S, Gloor M (2000) Direct comparison of skin physiology in children and adults
with bioengineering methods. Pediatr Dermatol 17:436–439
Fukudo M, Yano I, Masuda S et al (2005) Pharmacodynamic analysis of tacrolimus and cyclo-
sporine in living-donor liver transplant patients. Clin Pharmacol Ther 78:168–181
Gorodischer R, Burtin P, Verjee Z, Hwang P, Koren G (1997) Is saliva suitable for therapeutic
monitoring of anticonvulsants in children: an evaluation in the routine clinical setting. Ther
Drug Monit 19:637–642
Greenblatt DJ, Koch-Weser J (1976) Intramuscular injection of drugs. N Engl J Med 295:542–546
Gross AS (2001) Best practice in therapeutic drug monitoring. Br J Clin Pharmacol
52(Suppl 1):5S–10S
Herkes GK, Eadie MJ (1990) Possible roles for frequent salivary antiepileptic drug monitoring in
the management of epilepsy. Epilepsy Res 6:146–154
Hoogtanders K, van der Heijden J, Christiaans M, Edelbroek P, van Hooff JP, Stolk LM (2007)
Therapeutic drug monitoring of tacrolimus with the dried blood spot method. J Pharm Biomed
Anal 44:658–664
Ince I, de Wildt SN, Tibboel D, Danhof M, Knibbe CA (2009) Tailor-made drug treatment for
children: creation of an infrastructure for data-sharing and population PK-PD modelling. Drug
Discov Today 14:316–320
Irtan S, Azougagh S, Monchaud C, Popon M, Baudouin V, Jacqz-Aigrain E (2008) Comparison of

high-performance liquid chromatography and enzyme-multiplied immunoassay technique to
monitor mycophenolic acid in paediatric renal recipients. Pediatr Nephrol 23:1859–1865
Irtan S, Saint-Marcoux F, Rousseau A, Zhang D, Leroy V, Marquet P, Jacqz-Aigrain E (2007)
Population pharmacokinetics and bayesian estimator of cyclosporine in pediatric renal trans-
plant patients. Ther Drug Monit 29:96–102
Kearns GL, Abdel-Rahman SM, Alander SW, Blowey DL, Leeder JS, Kauffman RE (2003)
Developmental pharmacology–drug disposition, action, and therapy in infants and children.
N Engl J Med 18(349):1157–1167
Koal T, Burhenne H, R€ omling R, Svoboda M, Resch K, Kaever V (2005) Quantification of
antiretroviral drugs in dried blood spot samples by means of liquid chromatography/tandem
mass spectrometry. Rapid Commun Mass Spectrom 19:2995–3001
Koren G (1997) Therapeutic drug monitoring principles in the neonate. National Academy of
Clinical Biochemistry. Clin Chem 43:222–227
la Marca G, Malvagia S, Filippi L, Fiorini P, Innocenti M, Luceri F, Pieraccini G, Moneti G,
Francese S, Dani FR, Guerrini R (2008) Rapid assay of topiramate in dried blood spots by
a new liquid chromatography–tandem mass spectrometric method. J Pharm Biomed Anal
48:1392–1396
la Marca G, Malvagia S, Filippi L, Luceri F, Moneti G, Guerrini R (2009) A new rapid
micromethod for the assay of phenobarbital from dried blood spots by LC-tandem mass
spectrometry. Epilepsia 50:2658–2662
Li W, Tse FL (2010) Dried blood spot sampling in combination with LC-MS/MS for quantitative
analysis of small molecules. Biomed Chromatogr 24:49–65
Liu H, Delgado MR (1999) Therapeutic drug concentration monitoring using saliva samples.
Focus on anticonvulsants. Clin Pharmacokinet 36:453–470
Marquet P, Sauvage FL, Loustaud-Ratti V, Babany G, Rousseau A, Lachâtre G (2010) Stability of
ribavirin concentrations depending on the type of blood collection tube and preanalytical
conditions. Ther Drug Monit 32:237–241
Mei JV, Alexander JR, Adam BW, Hannon WH (2001) Use of filter paper for the collection and
analysis of human whole blood specimens. J Nutr 131:1631S–1636S
Mullangi R, Agrawal S, Srinivas NR (2009) Measurement of xenobiotics in saliva: is saliva an
attractive alternative matrix? Case studies and analytical perspectives. Biomed Chromatogr
23:3–25
Oellerich M, Barten MJ, Armstrong VW (2006) Biomarkers: the link between therapeutic drug
monitoring and pharmacodynamics. Ther Drug Monit 28:35–38
Okah FA, Wickett RR, Pickens WL, Hoath SB (1995) Surface electrical capacitance as a
noninvasive bedside measure of epidermal barrier maturation in the newborn infant. Pediatrics
96:688–692
Payen S, Zhang D, Maisin A, Popon M, Bensman A, Bouissou F, Loirat C, Gomeni R, Bressolle F,
Jacqz-Aigrain E (2005) Population pharmacokinetics of mycophenolic acid in kidney trans-
plant pediatric and adolescent patients. Ther Drug Monit 27:378–388
Peng B, Boddy AV, Cole M, Pearson AD, Chatelut E, Rubie H, Newell DR (1995) Comparison of
methods for the estimation of carboplatin pharmacokinetics in paediatric cancer patients. Eur J
Cancer 31A:1804–1810
Plard C, Bressolle F, Fakhoury M, Zhang D, Yacouben K, Rieutord A, Jacqz-Aigrain E (2007)
A limited sampling strategy to estimate individual pharmacokinetic parameters of methotrex-
ate in children with acute lymphoblastic leukemia. Cancer Chemother Pharmacol 60:609–620
Quattrocchi F, Karnes HT, Robinson JD, Hendeles L (1983) Effect of serum separator blood
collection tubes on drug concentrations. Ther Drug Monit 5:359–362
Rodbro P, Krasilnikoff PA, Christiansen PM (1967) Parietal cell secretory function in early
childhood. Scand J Gastroenterol 2:209–213
Rutter N (1987) Percutaneous drug absorption in the newborn: hazards and uses. Clin Perinatol
14:911–930
Sanquer S, Schwarzinger M, Maury S et al (2004) Calcineurin activity as a functional index of

immunosuppression after allogeneic stem-cell transplantation. Transplantation 77:854–858
Scheyer RD, Cramer JA (1990) Pharmacokinetics of antiepileptic drugs. Semin Neurol
10:414–420
Sch€utz E, Svinarov D, Shipkova M, Niedmann PD, Armstrong VW, Wieland E, Oellerich M (1998)
Cyclosporin whole blood immunoassays (AxSYM, CEDIA, and Emit): a critical overview of
performance characteristics and comparison with HPLC. Clin Chem 44:2158–2164
Self TH, Heilker GM, Alloway RR, Kelso TM, Abou-Shala N (1993) Reassessing the therapeutic
range for theophylline on laboratory report forms: the importance of 5–15 micrograms/ml.
Pharmacotherapy 13:590–594
Sheiner LB, Beal SL (1981) Some suggestions for measuring predictive performance.
J Pharmacokinet Biopharm 9:503–512
Sherwin CM, Svahn S, Van der Linden A, Broadbent RS, Medlicott NJ, Reith DM (2009)
Individualised dosing of amikacin in neonates: a pharmacokinetic/pharmacodynamic analysis.
Eur J Clin Pharmacol 65:705–713
Soldin OP, Soldin SJ (2002) Review: therapeutic drug monitoring in pediatrics. Ther Drug Monit
24:1–8
Sommerer C, Giese T, Meuer S, Zeier M (2009) Pharmacodynamic monitoring of calcineurin
inhibitor therapy: is there a clinical benefit? Nephrol Dial Transplant 24:21–27
Steinberg C, Notterman DA (1994) Pharmacokinetics of cardiovascular drugs in children.
Inotropes and vasopressors. Clin Pharmacokinet 27:345–367
‘t Jong GW et al (2000) Unapproved and off-label use of drugs in a children’s hospital. N Engl J
Med 343:1125
‘t Jong GW et al (2002) Unlicensed and off-label drug use in a paediatric ward of a general hospital
in the Netherlands. Eur J Clin Pharmacol 58:293–297
Takahashi H, Ishikawa S, Nomoto S, Nishigaki Y, Ando F, Kashima T, Kimura S, Kanamori M,
Echizen H (2000) Developmental changes in pharmacokinetics and pharmacodynamics of
warfarin enantiomers in Japanese children. Clin Pharmacol Ther 68:541–555
ter Heine R, Hillebrand MJ, Rosing H, van Gorp EC, Mulder JW, Beijnen JH, Huitema AD
(2009a) Quantification of the HIV-integrase inhibitor raltegravir and detection of its main
metabolite in human plasma, dried blood spots and peripheral blood mononuclear cell lysate
by means of high-performance liquid chromatography tandem mass spectrometry. J Pharm
Biomed Anal 49:451–458
ter Heine R, Rosing H, van Gorp EC, Mulder JW, Beijnen JH, Huitema AD (2009b) Quantification
of etravirine (TMC125) in plasma, dried blood spots and peripheral blood mononuclear
cell lysate by liquid chromatography tandem mass spectrometry. J Pharm Biomed Anal
49:393–400
ter Heine R, Rosing H, van Gorp EC, Mulder JW, van der Steeg WA, Beijnen JH, Huitema AD
(2008) Quantification of protease inhibitors and nonnucleoside reverse transcriptase inhibitors
in dried blood spots by liquid chromatography–triple quadrupole mass spectrometry.
J Chromatogr B Anal Technol Biomed Life Sci 867:205–212
Tod MM, Padoin C, Petitjean O (2001) Individualising aminoglycoside dosage regimens
after therapeutic drug monitoring: simple or complex pharmacokinetic methods? Clin
Touw DJ, Neef C, Thomson AH, Cost-effectiveness of Therapeutic Drug Monitoring Committee
of the International Association for Therapeutic Drug Monitoring and Clinical Toxicology
(2005) Cost-effectiveness of therapeutic drug monitoring: a systematic review. Ther Drug
Monit 27:10–17
Touw DJ, Westerman EM, Sprij AJ (2009) Therapeutic drug monitoring of aminoglycosides in
neonates. Clin Pharmacokinet 48:71–88
van der Heijden J, de Beer Y, Hoogtanders K, Christiaans M, de Jong GJ, Neef C, Stolk L (2009)
Therapeutic drug monitoring of everolimus using the dried blood spot method in combination
with liquid chromatography–mass spectrometry. J Pharm Biomed Anal 50:664–670
van Rossum HH, de Fijter JW, van Pelt J (2010) Pharmacodynamic monitoring of calcineurin
inhibition therapy: principles, performance, and perspectives. Ther Drug Monit 32:3–10
Walson PD (1998) Therapeutic drug monitoring in special populations. Clin Chem 44:415–419
Warner A, Privitera M, Bates D (1998) Standards of laboratory practice: antiepileptic drug
monitoring. National Academy of Clinical Biochemistry. Clin Chem 44:1085–1095
Wilhelm AJ, den Burger JC, Vos RM, Chahbouni A, Sinjewel A (2009) Analysis of cyclosporin A
in dried blood spots using liquid chromatography tandem mass spectrometry. J Chromatogr B
Anal Technol Biomed Life Sci 877:1595–1598
Zhao W, Elie V, Baudouin V, Bensman A, André JL, Brochard K, Broux F, Cailliez M, Loirat C,
Jacqz-Aigrain E (2010) Population pharmacokinetics and Bayesian estimator of mycophenolic
acid in children with idiopathic nephrotic syndrome. Br J Clin Pharmacol 69:358–366
Zhao W, Baudouin V, Zhang D, Deschênes G, Le Guellec C, Jacqz-Aigrain E (2009) Population
pharmacokinetics of ganciclovir following administration of valganciclovir in paediatric renal
transplant patients. Clin Pharmacokinet 48:321–328
Drug Delivery and Formulations
J€org Breitkreutz and Joachim Boos
Contents
1 Administration Routes and Drug Dosage Forms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92
1.1 Peroral Drug Delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93
1.2 Oromucosal Drug Delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 96
1.3 Rectal Drug Delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
1.4 Topical/Transdermal Drug Delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
1.5 Parenteral Drug Delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 98
1.6 Intranasal Drug Delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
1.7 Pulmonary Drug Delivery . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 100
2 Excipients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101
2.1 Exposure and Risk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 102
2.2 Impurities in Medicinal Products . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 103
3 Compliance Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 104
4 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 105
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 106
Abstract Paediatric drug delivery is a major challenge in drug development.

Because of the heterogeneous nature of the patient group, ranging from newborns
to adolescents, there is a need to use appropriate excipients, drug dosage forms and
delivery devices for different age groups. So far, there is a lack of suitable and safe
drug formulations for children, especially for the very young and seriously ill
patients. The new EU legislation will enforce paediatric clinical trials and drug
development. Current advances in paediatric drug delivery include interesting new
concepts such as fast-dissolving drug formulations, including orodispersible tablets
J. Breitkreutz (*)
Institut f€ur Pharmazeutische Technologie und Biopharmazie, Heinrich-Heine-Universit€at
D€usseldorf, Universit€atsstraße 1, 40225 D€
usseldorf, Germany
e-mail: joerg.breitkreutz@uni-duesseldorf.de
J. Boos
Klinik und Poliklinik f€
ur Kinder- und Jugendmedizin, Westf€alische Wilhems-Universit€at, 48149
M€ unster, Germany

92 J. Breitkreutz and J. Boos
and oral thin strips (buccal wafers), and multiparticulate dosage forms based on
mini-tabletting or pelletization technologies. Parenteral administration is likely to
remain the first choice for children in the neonatal period and for emergency cases.
Alternative routes of administration include transdermal, pulmonary and nasal drug
delivery systems. A few products are already available on the market, but others
still need further investigations and clinical proof of concept.
Keywords Paediatric drug formulations • Child-appropriate dosage forms •

Excipients toxicity • Drug delivery devices • Compliance
Abbreviations
ADI Acceptable daily intake

API Active pharmaceutical ingredient
DPI Dry powder inhaler
EMA European Medicines Agency
FAO Food and Agriculture Organization
GINA Global Initiative on Asthma
JECFA Joint Expert Committee on Food Additives
ODT Orally disintegrating tablet
PDE Permitted daily exposure
PIP Paediatric Investigation Plan
pMDI Pressured metered-dose inhaler
TSE Transmissible spongiform encephalitis
UK United Kingdom
WHO World Health Organization
1 Administration Routes and Drug Dosage Forms
Limited evidence-based information around acceptability and preference of dosage

forms in children are available, despite the fact that the therapeutic outcomes are
closely linked to it. An ideal formulation should be beneficial for all subsets of the
paediatric population, provide sufficient bioavailability of the active pharmaceuti-
cal ingredient (API), be palatable or at least acceptable, contain non-toxic, safe
excipients, enable a safe and easy administration, own socio-cultural acceptance
and provide precise advice in the product information (Table 1) (Breitkreutz and
Boos 2007). However, it is unlikely in most cases that a “one-fits-all” solution will
be available (Krause and Breitkreutz 2008). A variety of drug application routes
and appropriate dosage forms have to be considered. Due to economical reasons,
pharmaceutical companies and regulatory bodies have to elaborate compromises
between an ideal and a realistic approach. In the reflection paper Formulations of
Drug Delivery and Formulations 93
Table 1 List of basic criteria Sufficient bioavailability

for paediatric drug
Safe excipients
formulations
Palatable and/or acceptable properties
Acceptable dose uniformity
Easy and safe administration
Socio-cultural acceptability
Precise and clear product information
Parent/caregiver friendly
Choice for the Paediatric Population released by the European Medicines Agency
(EMA), the central regulatory office for medicinal products in the European Union,
a matrix on the acceptability of administration routes and dosage forms in relation
to age is provided (EMA 2006). The table is extremely helpful to elaborate a rough
idea on the opportunities and challenges of drug administration, but is not legally
binding. The source data of the matrix were expert opinions only and not scientifi-
cally derived results. However, when submitting the Paediatric Investigational Plan
(PIP) to the EMA, which is now general requirement in the drug license procedure
in Europe (Breitkreutz 2008), the provided table might be of additional benefit for
preparing the regulatory discussions. However, recent advances in pharmaceutical
technologies such as new drug dosage forms and novel functional excipients
urgently require a general revision of the present reflection paper (Krause and
Breitkreutz 2008).
1.1 Peroral Drug Delivery
Peroral drug administration is the preferred route of administration both in the

paediatric and the adult population. In general, peroral dosage forms can be
distinguished in solid or liquid forms. Semi-solid formulations, emulsions and
suspensions are generally sub-summarized under “liquid” dosage forms. Liquid
formulations offer the advantage of easy administration and a wide range for dose
adaptation, but they also display major disadvantages (Breitkreutz et al. 1999).
There are a limited number of safe excipients available for liquid formulations in
contrast to solid dosage forms (see section “Excipients”). In aqueous formulations,
there is a need for preservatives or antimicrobial devices to ensure the micro-
biological stability over storage and in-use conditions. Another major issue with
liquid formulations is taste (see section “Compliance Issues”). Masking unpleasant
taste of an API is much harder to achieve than with solid formulations where
introducing barriers like polymer coatings is an often used option. Dose accuracy
in using oral liquid preparations is another challenge. In a recently published survey
on antibiotic suspensions in marketed German products it became evident that the
accomplished dosing devices like dosing spoons and cups are inappropriate to
measure correct doses (Fig. 1), at least if lower doses than the standard doses are
160
140
120
% of labelled claim
100
80
60
40
20
0
Pipette Spoon 1/2 Spoon 1/4 Spoon
Amoxicillin Erythromycin
Fig. 1 Dosing errors when using measuring spoons in medicinal products (modified from
Breitkreutz et al. 1999). Percentage shows the actually measured dose in relation to the labelled
claim in all amoxicillin and erythromycin products available on the German market (top). The
deviating volumes are due to the inadequate calibration of the spoons provided in the package
(bottom: precisely measured 2.5 ml liquid, but graduation is still visible and hence, causes
overdosing)
required (Griessmann et al. 2007). Parents make numerous administration errors

especially when dosing the oral medication by dosing cups. Only 30% of the
parents can accurately (20% of the labelled dose) administer the correct dose
by a cup with printed graduations and 50% by a cup with etched marks. Significant
dosing errors (more than 40% deviation) were made by a quarter of all parents
enrolled in the study (Yin et al. 2010). Oral syringes are much more precise, but also
more expensive. Dose volumes may be critical, and it is considered that pre-school
children should not receive more than 5 mL and school-children should not be
dosed with more than 10 mL. It is evident that the less palatable the drug is, the
smaller the overall volume should be.
To overcome the disadvantages in liquid formulations, dispersible tablets and

effervescent dosage forms provide an alternative but are not without inherent
issues. The large volume of required diluent causes a burden of liquid to be
swallowed. The ingestion of bicarbonate in case of effervescent formulations may
lead to gastrointestinal malfunctions. Often the resulting sodium and/or potassium
content are rather high and particularly not suitable for renally impaired patients.
The general consensus on the acceptability of solid dosage forms provided in the
EMA reflection paper (EMA 2006) is that children younger than 6 years (newborns,
infants and pre-school children) have great difficulty with, or are even unable to
swallow solid oral dosage forms. The threshold of 6 years is mainly based on a
Dutch study on the consumption of dosage forms over age where a remarkable shift
from liquid to solid formulations was detected (Schirm et al. 2003). The swallowing
of monolithic dosage forms such as tablets or capsules can be trained, but some
children will not be capable to learn it at all (Czyzewski et al. 2000). However,
recent data from South Africa suggest that there is no significant difference in
refusal rates of children receiving liquid and solid formulations (Polaha et al. 2008).
There is ongoing research how the dimensions and geometries of monolithic dosage
forms may affect the acceptability and swallowing. Mini-tablets with 3-mm diam-
eter could be swallowed by a majority of 4-year-old children (Thomson et al. 2009).
Multifunctional tablets which can be splitted into pieces and then dissolved prior to
administration, but also swallowed may be another interesting option.
Swallowing issues are frequently overcome by crushing tablets or opening
capsules and adding the resulting powder to beverages or soft food despite proof
of accurate dosing, stability and bioequivalence. Sometimes the resulting powder is
further diluted with powdered excipients and repackaged in sachets or capsules for
extemporaneous dispensing with few, if any, compatibility and stability consider-
ation. It is often neglected that food may have variable quality and composition and
that food ingredients may reduce the API content. 6-Mercaptopurine for instance is
completely degraded within minutes by xanthinoxidase which is still active in milk
or milk products (Wessel et al. 2001). The validation of the prepared extemporane-
ous formulation is often poorly performed. In case of hydrochlorothiazide, it could
be demonstrated that neither the magistral capsules nor some in literature proposed
liquid formulations offer sufficient dose uniformity (Barnscheid 2008).
When tablets are not scored but yet split or cut to obtain the appropriate dose
or to facilitate swallowing, dose accuracy cannot always be ensured: the weight of
a split tablet can range from 50 to 150% of the actual half-tablet weight (van Santen
et al. 2002). However, when using improved tablet geometries accurate dose
adaptation can be performed for even one-eighth of the total dose (Kayitare et al.
2009). Only few products with scored tablets contain explicit information on
divisibility and procedures for splitting (Quinzler et al. 2006). Splitting tablets
into segments is not recommended with narrow therapeutic index drugs, potent
or cytotoxic APIs. Some solid dosage forms (e.g. saliva-resistant, enteric-coated,
sustained-release coated tablets, osmotically driven drug delivery systems) cannot
be manipulated without affecting taste, release properties, and possible therapeutic
effects, unless especially stated in the product information provided by the
Fig. 2 Multifunctional tablet for paediatric use: Coartem® (Novartis). The tablet can be dissolved
in glass or a small volume of liquid on a spoon prior to administration. The formulation is speci-
fically designed for malaria treatment of children in developing countries with high temperatures
and humidity
manufacturer in agreement with the regulatory authority (Breitkreutz et al. 1999).

The use of splitting devices does usually not improve the dose uniformity of the
obtained segments, and therefore, may also not replace the development of appro-
priate formulations.
A potentially very fruitful area for future research and development are so-called
“enabling formulations” verified by the pharmaceutical companies to provide a
defined diluent or dispersion vehicle which is mixed with the marketed solid dosage
forms, preferably multiparticulates such as granules (sprinkles), pellets or mini-
tablets. The resulting liquid or semi-solid formulation can be dosed intra-orally or
using devices the child likes. The recently introduced products Co-Artem®, a fixed-
dose antimalarial combination (Fig. 2), and Tracleer® for children, containing
bosentan for pulmonary arterial hypertension, have been designed as tablets with
breaking notches for splitting, but they can also be dissolved in water or at least
dispersed forming a suspension for facilitating the oral uptake.
1.2 Oromucosal Drug Delivery
Solid preparations which spontaneously disperse in the oral cavity (e.g. orodis-
persible tablets, thin film strips, oral lyophilisates) stand also on the periphery of
solids and liquids. There are exciting new opportunities and recent advances in this
area. Oral lyophilisates, e.g. based on the Zydis® technology, have been introduced
some years ago offering fast-disintegrating wafers instantaneously forming a drug
solution within a few seconds (Seager 1998). As the production of the lyophilisates
is quite energy and cost-consuming their use was limited to niche markets, e.g.
for antiemetic drugs in high-dose cancer therapy. By introducing new functional
excipients, such as ready-to-use powder mixtures for direct tabletting, new
opportunities arise. By these excipients, mostly composed of co-processed man-
nitol, binders and super-disintegrants, orally disintegrating tablets (ODTs) can be
developed offering almost the same disintegration profiles as oral lyophilisates, but
produced on conventional tabletting equipment (Brown 2003). An interesting new
approach has been recently introduced by combining the mini-tablet and the ODT
concept (Fig. 3). These orodispersible mini-tablets dissolve within a few seconds in
the mouth releasing the drug substance. In the best case only 2.5 mg drug can be
loaded into a 2-mm mini-tablet, so that multiple dosing might be necessary. An
unpleasant taste of the API may be another issue and could require taste-masking
measures which would further reduce the dose loading. Oral film strips are another
alternative in paediatrics and the first medicinal products, e.g. with antiemetic drugs
or cough medication, have been introduced (Garsuch and Breitkreutz 2010).
Depending on drug substance, the film area and height up to 70 mg, but usually
only 15–25 mg API can be included in an oral film piece. The limitation of the
orodispersible formulations in general is the poor drug load when maintaining
the fast-dissolving properties. However, in paediatric medicines numerous drug
molecules are used at low doses and are therefore potential candidates for oromu-
cosal drug preparations. Another challenge is that only few excipients are available
to improve medication’s palatability and that using these excipients might cause a
reduction of the maximum drug load. Moreover, it is to be noted that few studies
have been performed to assess appropriate age, stage of development, and dosage
form of choice regarding applicability, acceptability, and preference. Further it has
to be considered that the absorption profile may be complicated as some molecules
may be absorbed directly through the oral mucosa, but an uncertain ration of the
dose is absorbed after swallowing.
0s 4s 6s 8s 10s
Fig. 3 Orally disintegrating mini-tablet (diameter: 2 mm) rapidly losing shape and partly
dissolving in artificial saliva
1.3 Rectal Drug Delivery
The rectal administration route can be used for local (e.g. laxative or anti-
inflammatory) or systemic (e.g. antipyretic or anticonvulsive) treatment. The
administration of drugs by rectal formulations (e.g. suppositories, solution, soft
capsules or ointments) can result in a wide variability in the rate and extent of
absorption in children. The rectal administration of suppositories or enemas for
systemic effects may nevertheless be chosen because the patient cannot take
medication orally, because the oral dosage form is rejected as a result of palatability
issues or because immediate absorption is required in emergency cases such as
grand-mal seizures. However, the use of rectal preparations has major drawbacks.
When administering rectal preparations, there is always the danger of premature
expulsion. The rectal bioavailability is limited for a broad range of drug molecules
(e.g. levodopa, phenytoin and penicillins), compared with oral or intestinal absorp-
tion (Krause and Breitkreutz 2008). Last but not least, the rectal route is poorly
accepted by a number of patients and caregivers in certain countries and cultures.
1.4 Topical/Transdermal Drug Delivery
The development of the stratum corneum, the most prominent absorption barrier of
human skin, is complete at birth but is more perfused and hydrated than in older
children or adults. Therefore, neonates and infants have an underdeveloped epider-
mal barrier and are subject to excessive absorption of potentially toxic ingredients
from topically applied products. Only few transdermal products (e.g. contraceptive
drugs, caffeine, fentanyl, scopolamine, nicotine and methylphenidate) have been
tested or marketed for use in the paediatric population and predominantly have
targeted the elder children. Scopolamine is licensed only for children aged 14 years
or more because accidental overdoses in younger patients resulted in hallucinogenic
reactions. But still, the development of transdermal products in paediatric doses
could be beneficial for children who are unable to tolerate or accept oral
medications. The need for several sizes of patches to cover different doses might
be a further limitation. Sometimes adult patches are cut into pieces to obtain the
required size and dose. It is important to note that this is only possible with matrix-
type patches and, even then, the release kinetic may be modified and may cause
accidental overdosing.
1.5 Parenteral Drug Delivery
Parenteral administration routes enable drug administration to unconscious

and uncooperative patients. In the neonatal period and in emergency cases, the
intravenous administration of drugs is the most important therapeutic option.

Preterm and term neonates often receive all their medications by permanent venous
cannula. The drug delivery is often controlled by infusion pumps, such as the
Perfusor® technology, which allows an individual dose regimen.
Few drug products are available specifically designed for the subcutaneous or
intramuscular administration to children, whereas vaccines are provided with ade-
quate doses and design. Other parenteral routes of administration (e.g. intrathecal,
epidural, intraosseous, intraarterial or intracardiac) are used mostly in emergency
cases, for anaesthesia or in palliative care.
Drug solutions for infusion are often prepared extemporaneously by the hospital
pharmacy or by mixing products for parental use with marketed vehicles like
Ringer’s solution or isotonic sodium chloride solution. It is important to avoid
any drug–drug or drug–excipient interactions when mixing two or more medicinal
products. Ionic compounds may form ion pairs causing agglomeration and sedi-
mentation. Excipients such as detergents or bile acids may complex the drug
substance and thereby, change pharmacokinetics. By changing the pH value or
the ionic strength of the original products during the mixing process particles may
form that must be absent in intravenous, intraarterial or intracardiac preparations to
avoid embolism. Many active substances for injection, but also some for infusion,
are presented as lyophilized powders to be reconstituted before administration.
A number of products require withdrawal of a single dose or at least a particular
amount of the total dose if the product is intended for use in newborns, infants and
toddlers.
The facility to accurately measure the required small volumes is of particular
importance. There is a clinical need to limit the fluid uptake, especially in very
young children. On the other hand the volumes and surfaces of tubes, pumps and
cannulas have to considered when adjusting the flow rate and determining the total
volume. If not, it might be possible that not a single drug molecule may enter the
body of the child treated with a low dose and low volume of the drug. Hyperosmolar
injections or extreme pH values may irritate peripheral veins and produce throm-
bophlebitis, extravasation and pain. In many studies, various errors in preparing
and administering parenteral preparations have been reported. On paediatric wards
in Germany and UK, a huge rate of 34–48% of falsely prepared or administered
solutions have been estimated (Wirtz et al. 2003; Taxis and Barber 2004). The
errors include inappropriate choice of solvents, incorrect calculation of doses, too
fast infusion rates (especially for the bolus), omitting prescribed co-medication,
wrong or incomplete labelling of the prepared bottles, and various incompatibilities
between the ingredients of the mixture. In some cases, there was a fatal outcome
from the iatrogenic medication errors. Specially developed parenteral medications
for paediatric use are obviously advantageous. In a comparative study, significant
differences in bioavailability and other pharmacokinetic parameters could be
demonstrated for a specifically developed paediatric vial in comparison to an
extemporaneously prepared solution used for the treatment of newborns (Allegaert
et al. 2006).
Another critical issue is the migration of compounds of the applied medical

devices such as catheters, pumps, valves and also containers into the liquid prepa-
ration. The migration of plasticizers such as phthalates from polyvinylchloride bags
and tubes was determined as up to 400 mg/L diethylhexyl phthalate in fat emulsions
for parenteral nutrition (Wurdack et al. 2006). Other potential contaminants from
packaging materials and feeding tubes are monomers from the polymer synthesis,
leaching aluminium ions, antioxidants and colouring agents.
1.6 Intranasal Drug Delivery
This drug delivery into the nose provides fast and direct access to systemic cir-
culation without first-pass metabolism. Administration is not easy especially with
uncooperative children, but small volumes involved, rapidity of execution, feasi-
bility at home has made it more attractive, particularly for no-needle approach to
acute illnesses. Aerosols with an appropriate device can avoid swallowing and
is more precise in terms of dose. APIs such as benzodiazepines, fentanyl,
diamorphine, midazolame and ketamine have been used successfully via this
route. The key issue is to guarantee the released dose from a single actuation
from the device, especially for children as the dose is low and small deviations
from the intended dose may critically harm the patients.
1.7 Pulmonary Drug Delivery
Inhalative therapy is a major problem in paediatric drug delivery that comprises

different aspects such as drug formulation, inhaled particle size and shape, device
design and also physiological and psychological issues (Krause and Breitkreutz
2008). Still, the amount of drug deposited in the lung after using an inhalation
device is often small in adults, but even less in children. Today, paediatric inha-
lative formulations are restricted to treat pulmonary disease like asthma locally and
are not intended for a systemic treatment.
Compared to adults, children have lower tidal volumes, smaller functional
residual capacity and shorter respiratory cycles. The distances and volumes of
children’s airways and the throat differ from the adult form and therefore influence
drug deposition in the lungs. As a result the pulmonary deposition is mainly
hampered by lower breathing volumes, short residence times in the airways and
insufficient cooperation of the child.
Very young children are obligate nose breathers which can result in the total loss
of drug particles before entering the lungs.
Several studies suggest that drug particle sizes should be adapted for use in
children (Sch€uepp et al. 2005; Janssens et al. 2003). This is not only a problem of
crystal engineering, but also of drug formulation and device development. Smaller
particles deposit more peripherically and less in the upper airways whereas large
particles mostly stay in the mouth or throat by impaction to the endothelial cells. In
the case of dry powder inhalers (DPI) with interactive powder mixtures the outer
deposition of large particles made from carriers like lactose is intended, but the
smaller drug particles should enter the lung. In this particular case drug deposition
in the lung is a function of breathing abilities (to release the total dose, to separate
drug and excipients and to enable the direct flow of micronized drug particles into
the lung), of the formulation (which excipients, which drug crystals) and of the
device (breathing resistance, actuation, mouth adapter). It might be possible that
various devices and formulations would be needed for the same drug to suit the
requirements and properties of different age groups.
Pressured metered-dose inhalers (pMDI) have been sometimes successfully
employed in the paediatric population. These products are designed to deliver a
unit dose at high velocity with small particle size. However, self-administration is
difficult for younger patients with reduced coordination abilities and less compli-
ance consciousness.
To decrease oropharyngeal impaction and optimize utilization, various spacers
can be used. Face masks enable the use of pMDI for very young infants whereas
DPIs are only suitable for children with enough inspiratory flow to trigger particles’
release and transport the particles deep in the lung. Nebulizers are applicable for all
ages but very few are portable yet. Guidance for use of different inhaler types (i.e.
nebulizers, pMDI and DPI) has been established by the Global Initiative on Asthma
(GINA), a panel of clinical experts who look at the various inhaler types, their
features, and patient experience. Their guidance has been incorporated in national
regulatory guidance throughout the world. The most appropriate device should be
selected for each child. Children younger than 4 years should use a pMDI plus a
spacer with face mask or a nebulizer with face mask. Children aged 4–6 years should
use a pMDI plus a spacer with mouthpiece, a DPI, or, if necessary, a nebulizer with
face mask. For children using spacers, the spacer must fit the inhaler, and particular
attention should be paid to ensure that the spacer fits the child’s face. Children of any
age older than 6 years who have difficulty using pMDIs should use a pMDI with a
spacer, breath-actuated inhaler, DPI, or nebulizer. Particularly among children
younger than 5 years, inhaler techniques may be poor and should be monitored
closely. In order to improve devices and formulations, the development of in-vitro
models fully reflecting the physiological conditions at different age groups of
children are under development in our working group. The aim is to improve today’s
deposition rates by taking the differences in airways and capabilities into account.
2 Excipients
Pharmaceutical excipients are falsely regarded as “inactive ingredients” or “inert

substances” (McIntyre and Choonara 2004). Excipients show similar pharmacoki-
netic profiles like APIs, with absorption, distribution into organs, metabolization
Table 2 Some excipients with elevated toxicological risk and severe outcome in children
reported in the literature
Excipient Patients at risk Administration Adverse reactions
Benzyl alcohol <6 months Oral, parenteral Neurotoxicity, metabolic
acidosis, >100 deaths
Polyethylene glycol <6 months Parenteral Metabolic acidosis
(Macrogol)
Aluminium salts <6 months Oral, parenteral Encephalopathy, microcytic
anaemia, osteodystrophy
Propylene glycol <12 months Oral, parenteral Neurotoxicity, seizures,
hyperosmolarity, death
Menthol <12 months Oral, nasal, dermal Bronchoconstriction, death
application to
face or breast
Diethylene glycol <18 years, all ages Oral Metabolic acidosis,
hyperosmolarity, >500
deaths
Benzalkonium Hypersensitive Oral, nasal, ocular Bronchoconstriction in
chloride patients, all ages hypersensitive patients,
loss of microvili function
Parabens <18 years, all ages Oral, parenteral, Allergies, contact dermatitis,
ocular, topical carcinogenic potential
Sulfites, bisulfites Hypersensitive Oral, parenteral Anaphylactic reactions
patients, all ages
with drug interaction capacity and elimination. To evaluate pharmaceutical excipients

some predictive methods and agreed limits have been adapted from the risk assessment
of food additives such as the Acceptable Daily Intake (ADI), established by the Joint
Expert Committee on Food Additives (JECFA) of the World Health Organisation
(WHO) and world’s Food and Agriculture Organisation (FAO). However, it is ques-
tionable whether these limits can be used for the paediatric population (see Table 2).
The toxicity is mainly attributed to children’s insufficient or varying metabolic capac-
ity in the first years of life. Mixing up of excipients in formulations, accidentally used
high amounts of excipients, errors in correct labelling of ingredients and unforeseen
toxic effects of excipients have been reported (McIntyre and Choonara 2004). Plenty of
these unwanted events have been linked to diethylene glycol which was used as co-
solvent in pharmaceutical preparations (84 deaths in Nigeria 2009), in tooth-paste
(China 2009) or as an impurity in other excipients such as glycerol or propylene glycol
(at least 21 deaths in Panama 2006 and 28 in Bangladesh 2009). Between 1995 and
today at least 500 children died from iatrogenic intoxication with diethylene glycol.
2.1 Exposure and Risk
The risk of children exposed to pharmaceutical excipients is linked to their age and
thereby, the maturation of organs and functions of the metabolic systems. The
excipients may maintain for longer period in the juvenile body due to reduced meta-
bolic capacity or minor renal elimination. They can easily enter the brain as the
blood–brain barrier is more permeable than in adults. They can activate the immune
system of the maturing organism and may induce allergies or anaphylactic reactions.
Excipients with an elevated risk in paediatrics linked to the pharmacokinetic
properties are benzyl alcohol, ethanol, propylene glycol, polyethylene glycol and
aluminium salts (such as aluminium stearate or aluminium hydroxides). Benzyl
alcohol caused the “gasping syndrome” first described in 1981 by the accumulation
of metabolites such as benzaldehyde and benzoic acid in blood (metabolic acidosis)
and brain (neurotoxicity) causing more than 100 deaths worldwide (Gershanik et al.
1981). Metabolic acidosis is also a problem associated with high intake of polyethyl-
ene glycol and propylene glycol. Propylene glycol is regarded as very safe in the adult
population. There is no limit to be considered when using propylene glycol in
adulthood. In syrups for oral use it is often used as solvent, co-solvent or as a
replacement for a preservative at very high concentrations. There have never been
any reports on neurotoxic effects in adolescents and school-children. But in neonates,
especially in low-weight newborns and pre-term babies, numerous deaths, severe
brain damage and life-long handicaps have been reported (American Academy of
Pediatrics 1997; MacDonald et al. 1987). Propylene glycol and its metabolites may
enter the brain and may cause seizure and other neurotoxicological effect.
The neurotoxic potency of ethanol is well known, but the long-term effects of
low ethanol doses are still under discussion. Ethanol levels in pre-term neonates or
neonates with low birth weight have been recently investigated and raise concerns
(Whittacker et al. 2009). In some paediatric patients, even lower limits must be
considered, e.g. in children with liver and kidney malfunctions. In paediatric
dialysis patients the use of propylene glycol, polyethylene glycols and aluminium
salts should be completely prohibited. Hypersensitive patients may adversely react
on allergen presented in the formulation such as parabens, benzalkonium chloride,
colourants (azo dyes), sulfites, starches (glutens) or wool wax (Breitkreutz and
Boos 2007). For parabens agonistic activity at hormone receptors is discussed and
propyl paraben has been recently deleted from the list of permitted food additives in
the EU. In some cases, the immune system will cause anaphylactic reaction which
may be severe and live-threatening (dextran, sodium bisulfite, macrogolglycerol-
ricinoleate). Moreover, it has to be considered that some children may suffer from
rare diseases such as phenylketonuria, hereditary fructose intolerance and lactose
intolerance. In phenylketonuria, the use of aspartame must be prohibited as it is a
phenylalanine source. In fructose intolerance, the intake of the excipients fructose,
sucrose and sorbitol should be avoided.
2.2 Impurities in Medicinal Products
The fatal intoxications with diethylene glycol as an impurity lead to a discussion

about the quality of pharmaceutical excipients. Despite chemical impurities
some more potential contaminants have been identified in materials derived from
mammalian species with transmissible spongiform encephalitis (TSE), excipients
with potential viral load, and substances with potential endotoxin and pyrogen
load.
Some excipients in medicinal products are not labelled as they are only present
in traces. Residual solvents, for instance, are used in the manufacturing process
to solve a drug substance, a film former or a granulation binder. Residuals of
catalysts from the synthesis of the compounds and salts from heavy metals from
synthesis or packaging materials may be contained. Plasticizers from plastic
containers may migrate into the liquid phase (see section “Parenteral Drug
Delivery”). The residual burden of solvents is a good example, how difficult a
risk assessment in paediatric is: The amount of residuals of organic solutes in a
finished product is limited by the Permitted Daily Exposure (PDE). The organic
solvents are categorized into three classes by the toxic potency. Solvents with
highest toxicity are listed in class I, the less problematic solvents in class III.
However, both the categorization and the fixed limits have been derived from risk
assessment for adults, namely a woman with 50 kg body weight. It is not probable
that these limits match the paediatric situation. Therefore, for the PIP procedure
and for the market licensing procedure it is recommended to reduce the burden of
potential contaminants as far as possible. Alternative manufacturing technologies
such as aqueous film coating, dry powder coating, lipid coating and aqueous or
solvent-free granulation methods are highly demanded and should be applied for
paediatric medicines whenever possible.
3 Compliance Issues
Compliance and concordance issues have multivariate complex origins but an

unacceptable taste is one major compliance issue (Cram et al. 2009). Two factors
make taste preference and palatability critical in paediatric adherence. The dosage
forms most commonly employed for paediatric formulations are liquids and
orodispersible tablets. A perceived unpleasant taste is much more evident with
these dosage forms than when a drug is administered as a conventional solid oral
dosage form. Taste-masking of the unpleasant taste can be better achieved by
coating the drug crystals or the complete dosage form by polymers (film-coated
tablets) or sugars (dragees). It is widely believed that children younger than 6 years
have more distinguished taste perception than older children and adults. Therefore,
development of oral formulations for this age group is rather challenging. Taste
buds and olfactory receptors are fully developed in early infancy and a profound
aversion to bitter tasting substances is pronounced in all children of this age group.
Bitter taste perception is obviously a safety and protection measure to prohibit the
intake of toxic plant materials by the neonates and toddlers. By the recent intro-
duction of analytical instruments, so called electronic tongues, the development
of child-appropriate medicines is facilitated. Although these instruments are not

reliable for absolute taste prediction, they offer the opportunity to rationalize the
development by testing the taste-relevant molecules (APIs or excipients) and
evaluating the effectiveness of taste-masking strategies (Woertz et al. 2010). In
addition to taste formulation’s smell, texture and visual appearance are important
factors in the development of paediatric dosage forms for oral use.
Beside the taste perception children’s adherence to therapy is affected by their
cognitive skills, their acceptability or ability to swallow, their socio-cultural envi-
ronment and personal strengths, affected or not by their disease. Recently, some
new medicinal products have entered the market in order to avoid the stigmatization
of the juvenile patient. Examples are improved injection devices with fancy design,
e.g. with insulin or growth hormone, transdermal patches with fentanyl and pulsa-
tile drug formulations with methylphenidate. In order to prevent school-children
with attention deficiencies disorders from stigmatization, capsule formulations with
mixed uncoated and coated pellets with delayed drug-release (e.g. Medikinet®
retard) and oral osmotically releasing pulsed system (Concerta®) have been
introduced to save the dosing during school-time.
The adherence to the therapy regimen is also related to the capabilities of the
caregivers, which are the parents of the children in most cases. The education of
parents and children plays a major role in dosing errors. Although it is even alerting
that the use of dosing cups results in about 25% of dosing procedures to major
dosing errors in general, the incidence of dosing errors almost doubles with limited
literacy (Yin et al. 2010). But even with clear instructions it seems to be difficult to
administer liquid preparations correctly. In another study only 66% of the
volunteers measure the correct volume with a syringe and even less, 14.6% using
a dosing cup although the majority of people strongly believed it would be correct
(Sobhani et al. 2008). It can be concluded that clear advice and instructions, better
visually than in words, must be provided with the medicinal products.
4 Conclusions
Drug delivery to children is still a major challenge. Key issues are age-appropriate
formulations, safety of excipients, suitability of drug delivery devices and therapy
compliance. Some improvements have been made recently. The most promising
in oral drug delivery are orodispersible mini-tablets and thin film strips. In
parenteral drug delivery age-adapted devices and profound knowledge on the
preparation of extemporaneous or enabling formulations are of major importance.
In pulmonary drug delivery new in vitro deposition models, adapted to physio-
logical properties of children, may lead to better formulations and delivery
devices. The new EU formulation will stimulate the research and development
in paediatric medicines. Hopefully we will be able to match the unmet needs of
paediatric patients soon.
References
Allegaert K, Anderson BJ, Vrancken M (2006) Impact of a paediatric vial on the magnitude of
systematic medication errors in neonates. Paediatr Perinat Drug Ther 7:59–63
American Academy of Pediatrics (1997) “Inactive” ingredients in pharmaceutical products – a
review. Pediatrics 99:268–278
Barnscheid L (2008) Kindgerechte Arzneizubereitungen mit diuretischen Wirkstoffen, Disserta-
tion HHU D€usseldorf
Breitkreutz J (2008) European perspectives on pediatric formulations. Clin Ther 30:2146–2154
Breitkreutz J, Boos J (2007) Paediatric and geriatric drug delivery. Expert Opin Drug Deliv
4:37–45
Breitkreutz J, Wessel T, Boos J (1999) Dosage forms for peroral administration to children.
Paediatr Perinat Drug Ther 3:25–33
Brown D (2003) Orally disintegrating tablets: taste over speed. Drug Deliv Technol 5:34–37
Cram A, Breitkreutz J, Desset-Brèthes S et al (2009) Challenges of developing palatable oral
paediatric formulations. Int J Pharm 365:1–3
Czyzewski DI, Runyan D, Lopez MA (2000) Teaching and maintaining pill swallowing in HIV-
infected children. AIDS Read 10:88–94
European Medicines Agency (EMA) (2006) Committee for Medicinal Products for Human Use.
Reflection paper: formulations of choice for the paediatric population. EMEA/CHMP/PEG/
194810/2005
Garsuch V, Breitkreutz J (2010) Comparative investigations on different polymers for the
manufacturing of fast-dissolving oral films. J Pharm Pharmacol 62:539–545
Gershanik JJ, Boecler B, George W et al (1981) The gasping syndrome – benzyl alcohol (BA)
poisoning? Clin Res 29:895A
Griessmann K, Breitkreutz J, Schubert-Zsilavecz M et al (2007) Dosing accuracy of measuring
devices provided with antibiotic suspensions. Paediatr Perinat Drug Ther 8:61–70
Janssens H, De Jongste J, Hop W et al (2003) Extra-fine particles improve lung delivery of inhaled
steroids in infants. Chest 123:2083–2088
Kayitare E, Vervaet C, Ntawukulilyayo JD et al (2009) Development of fixed dose combination
tablets containing zidovudine and lamivudine for paediatric applications. Int J Pharm
370:41–46
Krause J, Breitkreutz J (2008) Improving drug delivery in paediatric medicine. Pharm Med
22:41–50
MacDonald MG, Getson PR, Glasgow AM et al (1987) Propylene glycol: increased incidence of
seizures in low birth weight infants. Pediatrics 79:622–625
McIntyre J, Choonara I (2004) Drug toxicity in the neonate. Biol Neonate 86:218–221
Polaha J, Dalton WT, Lancaster BM (2008) Parenteral report of medication acceptance among
youth: implications for everyday practice. South Med J 101:1106–1112
Quinzler R, Gasse C, Schneider A et al (2006) The frequency of inappropriate tablet splitting in
primary care. Eur J Clin Pharmacol 62:1065–1073
Schirm E, Tobi H, de Vries TW et al (2003) Lack of appropriate formulations of medicines for
children in the community. Acta Paediatr 92:1486–1489
Sch€uepp K, Jauernig J, Janssens H et al (2005) In vitro determination oft he optimal particle size
for nebulized aerosol delivery to infants. J Aerosol Med 18:225–235
Seager H (1998) Drug-delivery products and the Zydis fast-dissolving dosage form. J Pharm
Pharmacol 50:375–382
Sobhani P, Christopherson J, Ambrose PJ et al (2008) Accuracy of oral liquid measuring devices:
comparison of dosing cup and oral dosing syringe. Ann Pharmacother 42:46–52
Taxis K, Barber N (2004) Incidence and severity of intravenous drug errors in a German hospital.
Eur J Clin Pharmacol 59:815–817
Thomson SA, Tuleu C, Wong ICK et al (2009) Minitablets: a new modality to deliver medicines to
preschool-age children. Pediatrics 123:e235–e238
Van Santen E, Barends DM, Frijlink HW (2002) Breaking of scored tablets: a review. Eur J Pharm
Biopharm 53:139–145
Wessel T, Breitkreutz J, Ahlke E et al (2001) Problems in the maintenance therapy with
mercuptopurine tablets [in German]. Krankenhauspharmazie 22:325–329
Whittacker A, Currie AE, Turner MA et al (2009) Toxic additives in medication for preterm
infants. Arch Dis Child Fetal Neonatal Ed 94:F236–F240
Wirtz V, Taxis K, Barber N (2003) An observational study of intravenous medication errors in the
United Kingdom and in Germany. Pharm World Sci 25:104–111
Woertz K, Tissen C, Breitkreutz J et al (2010) Performance qualification of an electronic tongue
according to the ICH guideline Q2. J Pharm Biomed Anal 51:497–506
Wurdack W, Kittlaus A, Pecar R et al (2006) Release of components from primary package
materials and their migration into drug and nutrition solutions [in German]. Krankenhau-
spharmazie 27:334–339
Yin HS, Mendelsohn AL, Wolf MS et al (2010) Parents’ medication administration errors. Arch
Pediatr Adolesc Med 164:181–186
Part II
Development of Pediatric Medicines
Development of Paediatric Medicines: Concepts
and Principles
Klaus Rose and Oscar Della Pasqua
Contents
1 Evolution of Paediatric Drug Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
2 Challenges in the Transition from Retrospective to Prospective Assessment
of Medicines for Children . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
3 Priorities and Unmet Needs in Paediatric Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115
3.1 Essentials in Paediatric Clinical Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 116
4 Incentives and Rewards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118
5 A New Role for Regulatory Authorities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
6 Strategy for a Paediatric Development Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119
7 Limitations of Paediatric Legislation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 121
8 Future Perspectives in Regulatory Affairs and Public Health Policies . . . . . . . . . . . . . . . . . . 122
9 Foreseeable and Unforeseeable Developments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123
10 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124
Abstract The term “off-label use of drugs in children” is common to current

medical practice. A look into the historical context helps to elucidate the frame-
work for the use of medicines in children. Proper drug labels are relatively new
in history. They emerged half a century ago when U.S. legislation forced
manufacturers to prove the safety and efficacy of drugs by adequate clinical
K. Rose (*)
klausrose Consulting, Pediatric Drug Development & More, Birsstrasse 16, 4052 Basel,
Switzerland
e-mail: rose@granzer.biz
O. Della Pasqua
Division of Pharmacology, Amsterdam Center for Drug Research, Leiden University, Einsteinweg
55, P.O. Box 9503, 2300 RA Leiden, The Netherlands
Clinical Pharmacology & Discovery Medicine, GlaxoSmithKline R&D, Stockley Park, Uxbridge
UB11 1BT, United Kingdom
e-mail: odp72514@gsk.com

112 K. Rose and O. Della Pasqua
trials. Today pharmaceutical progress is so obvious and well established that the
discrepancy between its benefit for adults as compared to children started to be
perceived by champions in different institutions. There is an increased under-
standing of the child’s physiology during developmental growth, of the matura-
tion of enzyme systems, of the pharmacokinetics and pharmacodynamics and of
the differences in disease processes. The involved institutions include legislators,
government, regulatory authorities, academic scientists, pharmaceutical com-
panies, the WHO, to name just the most prominent ones, but there are many
more. Driving forces for the improvement of medicines for children include
societal priorities, the involvement of science, the mission of regulatory authori-
ties the role of clinical pharmacologists, paediatricians, and the characteristics of
our market-driven economy with its chaotic, contradictory and lively elements.
We do not live in an ideal world, but there is progress, and children are likely to
benefit from it.
Keywords Paediatric drug development • Medicines for children • Neglected

diseases • Incentives for paediatric clinical research • Public health • Regulatory
authorities • Priorities in paediatric drug development • Historical context of
paediatric drug development
1 Evolution of Paediatric Drug Development
Since its earliest origins, mankind, adults and children were challenged by
accidents, diseases and hazards that required medical treatment. Until less than a
century ago, women used to get pregnant at a very young age and usually gave birth
to several children. The death rate of these children was horrific by today’s
standards, as was the frequency of mothers dying at childbirth. This situation
occurred despite health care providers being available during all these millennia
and centuries. Based on current medical knowledge little of what they could deliver
was helpful, albeit state-of-the-art at the time. And these professionals had an
amazingly high social reputation, with a status between priests and physicians. In
parallel to the evolvement of modern medicines, the principles of professional
health care practice and the criteria for the recognition of effective treatments
also changed dramatically over the last centuries, with an ever accelerating speed
of change. To a great extent, scientific principles have replaced common belief,
tradition and superstition, all of which pervaded therapeutics over the centuries.
The reputation of a member of the medical community has today something to do
with his or her actual knowledge and therapeutic skills.
On the other hand, there is today an increasingly complex layer between the
patient receiving treatment and the health care professional dispensing it. Thera-
peutics is based on an intricate process that we will define here as evidence
synthesis. To assess the efficacy of a new drug, clinical trials are performed in
hundreds or thousands of patients. The implementation and execution of these
Development of Paediatric Medicines: Concepts and Principles 113
trials may involve multiple clinical research centres, which can be thousands of
miles away, in another country, in another continent, or spread worldwide. To
ensure that such trials adhere to the state-of-the art standards and procedures,
a network of regulation exists that is recognised by national authorities and
professionals worldwide (ICH 2010). In addition, regulatory authorities have
established a comprehensive mechanism of monitoring and auditing. A clinical
trial performed in China, India and Latin America may be audited by the FDA
(2010), the EMA (2010), or even jointly by these two agencies. All the informa-
tion gathered in a trial will at the end be processed, analysed and reported. The
submission of such evidence to regulatory authorities triggers an evaluation
process that may lead to approval or rejection of the proposed treatment or
therapy. If the evaluation is positive, the evidence from clinical trial results
becomes part of the label or summary of product characteristics (SPC) and of
the patient information leaflet. In contrast to long gone times, none of the infor-
mation regarding the indication, efficacy and safety of a treatment originates from
the medical doctor who prescribes it. Instead, it is the result of pharmaceutical
physicians, clinical scientists and other professionals who contribute to drug
development. In this chapter, we try to grasp how this layer between patient and
caregiver is being adapted to the specific needs of children.
The advent of industrialisation in combination with the awakening of medical
sciences towards the end of the nineteenth century resulted in the identification and
subsequent availability of new, efficacious medicines. This process has since then
yielded powerful medications (e.g. antibiotics or steroids) for the treatment of
adults. These drugs have been subsequently brought into paediatrics based on
empiricism, an approach which has prevailed until recently.
Despite the development of pharmacology and clinical pharmacology as
disciplines with increasing understanding of the mode of action of available
drugs, including the requirements to demonstrate their efficacy, the formal assess-
ment of treatment effects in children has remained limited due to cultural,
practical and ethical reasons. In addition, the tools for the evaluation of efficacy
and safety in children have been historically questionable by current standards in
clinical research. Drugs developed early in the last century showed strong effi-
cacy, but had also the potential for serious side-effects and adverse events. The
first major tragedies (Taussig 1962; Wax 1995), leading to multiple deaths and
malformations resulted in the mandate for manufacturers in the USA to yield
proof of safety (1936) and efficacy (1960s, Kefauver-Harris amendments) (Hilts
2003; Rose and van den Anker 2010; Stoetter 2007). Since then, therapeutic
claims have to be demonstrated by properly designed clinical trials and other
measures. The requirement for data supporting product claims represented the
beginning of the modern drug labelling system. The initial deep, nearly blind
confidence in modern medications was in this way replaced by the need to impose
control. In the United States, the Food and Drug Administration (FDA) became
responsible for the assessment of the scientific and quality aspects of drug
development. Comparable legislation followed in Europe, with some variations
in the implementation in different individual countries.
The cultural and historical differences in medical practice in Europe have

prevented consensus and created discrepancies in the level of evidence deemed
appropriate for many adult indications and for most paediatric labels. The
main consequence of such discrepancies includes the lack of clear dosing recom-
mendations (i.e., dosing regimen) and formal proof of efficacy (i.e., therapeutic
indication) for the majority of approved drugs. The acceptance of this practice by
paediatricians, regulatory agencies, clinical researchers and parents has evolved into
extensive off-label use of medicines in children from the beginning of the existence
of modern labels. As a consequence of this practice, most companies in the United
States and in Europe introduced paediatric disclaimers to avoid litigation.
Cultural perspectives about childhood have also influenced the way scientific
evidence was generated. Until recently children have been regarded and treated as
small adults, with dosing recommendations varying between rough estimates (chil-
dren get half a tablet, babies a quarter) and empirical formulas, which varied by
country and sometimes across regions or hospitals within the same country.
Protagonism in research has enforced empiricism in therapeutic utilisation of
drugs in children. From a prescriber’s perspective, such practice has been justified
by the need for easy rules and prevention of prescription errors. Furthermore,
personal convictions often dominated the choice of eminent scientists. Still today,
the question regarding what is the right dose for children remains often unanswered
(Cella et al. 2010).
The awareness about the need for a dedicated programme for paediatric
medicines exemplifies the slow shift in paradigm we are currently experiencing
in drug development. In contrast to the perception of the 1960s, which considered
evidence for safety and efficacy of a drug in adults sufficient to establish its use in
children, today’s society has become more sceptical and more demanding. In
addition to a specific ICH guideline on paediatric drug development (ICH E11
2010), which has been in force since 2000, the United States and European Union
paediatric regulations have introduced clear requirements for drug approval and
label claims that demand more than just scattered scientific evidence from drug use
in children. Safety and efficacy need to be proven based on a well-thought devel-
opment plan adapted to the specific therapeutic needs of children. The regulatory
authorities in the United States and Europe have had and still have a key role in
driving forward this change.
Since the dawning of modern medicine development, our understanding of the
differences between adults and children in terms of (patho)physiology and in
pharmacokinetics (i.e., what the body does with the drug) and pharmacodynamics
(i.e., what the drug does with the body) has expanded considerably. In parallel,
advances in the assessment of exposure–response relationships have provided tools
for exploring experimental designs and optimising the evaluation of pharmacoki-
netics, efficacy and safety in children. Clinical pharmacology has also supported the
development of increasingly sophisticated knowledge on formulations and on the
optimisation of drug delivery. Academic paediatric clinical pharmacology research
has so far focused on drugs that were on the market and then systematically
explored whether they could and should be used in children or not.
2 Challenges in the Transition from Retrospective

to Prospective Assessment of Medicines for Children
It has not become yet evident to the international community that the current
European legislation has introduced an unprecedented revolution. It forces phar-
maceutical industry and researchers across all therapeutic areas to consider the
future paediatric use of new chemical or biological entities, which are neither on
the market, nor available to the adult population yet. This poses another important
challenge: informal benchmarking from prior therapeutic utilisation in adults
will not be available at the time a new drug or biological is first administered to
children. The long-lasting arguments that in the past supported the empiricism
used by paediatricians and paediatric pharmacologists will have less and less
space in the years to come. Off-label use will not be supported by evidence of
safety and efficacy in adults at the same extent post-launch data have provided in
the past.
In contrast to the retrospective evaluation of a drug’s pharmacokinetics, phar-
macodynamics or clinical profile, which has been driven by academic research,
considerations about the clinical development of new medicines and future use of a
new compound in children will require direct involvement of the pharmaceutical
industry and potentially other sponsors. The need to establish partnerships, to foster
critical mass in academia and to enable effective public–private partnerships or
other collaborative efforts has, however, not been defined by the law. This repre-
sents the single most important challenge to the success of this new era in paediatric
drug development.
In summary, the evidence supporting paediatric drug utilisation is evolving from
a rather simple research activity within the realms of academic expert groups to a
global multidisciplinary effort where relevant stakeholders must work together.
However, modern society is complex and cooperation cannot be taken for granted,
particularly when different interests are at stake. Collaboration is not the result of
logical thinking nor is it based on effective use of resources and expertise towards a
common goal. It is imposed by a framework created by the paediatric legislation,
the results of which are just beginning to become visible.
3 Priorities and Unmet Needs in Paediatric Diseases
Priorities and unmet medical needs vary across geographic regions not only
because of biological, clinical and demographic reasons, but also due to political,
economical and social differences in the perception of the implications of disease
on child health and well-being. Let’s take as example two diseases which are
currently the focus of various research efforts: attention-deficit hyperactivity dis-
order (ADHD) and malaria. In the United States, ADHD is perceived as a develop-
mental disorder that requires pharmaceutical treatment to facilitate school
advancement of children, reducing the burden of parents and teachers. The same
disorder is perceived differently in Europe. On the other hand, malaria pervades the
lives of millions of children in Africa. Which of these two diseases should be
prioritised in terms of R&D efforts and health care policies? Many voices may
advocate malaria, but the answer to this question is complex and remains a social
and ethical dilemma as long as the priorities of the major players depend primarily
upon return-of-investment (RoI).
The majority of organisations in a market economy will have to consider direct
or indirect return of investment to fulfil their social and economic role. Serious non-
profit organisations and private–public partnerships, such as Drugs for Neglected
Diseases Initiative (DNDi 2010) and Medicines against Malaria Venture (MMV
2010) have a research agenda and predefined targets to meet. Many more stake-
holders can be found by web search engines, including charities, African govern-
ments, the United Nations, the World Health Organisation (WHO 2010) and the
Bill and Melinda Gates foundation (Gates Foundation 2010), all of which have their
own agenda.
The aforementioned issues are not addressed by the legislation on medicines for
children. In market-driven drug development, it is the management of individual
companies that decides which therapeutic targets will be included into the R&D
portfolio. A company has to aim for long-term survival, irrespective of the ethos
and social responsibilities it may endorse. To survive in a global economy,
enterprises must be able to maintain revenue. However, it is also true that there
are millions of children on this planet that have diseases that could be treated with
medications that are already available, but not accessible to the patients in need.
There is no single solution to this and many other dilemmas. A different, joint
public–private partnership model might be considered which would be recognised
beyond the regulatory and geographical borders of single countries. Without an
integrated, long-term action plan, it is unlikely that the needs of vulnerable popu-
lations, whether ADHD patients in the United States or malaria-infected children
in Africa, will be duly addressed.
3.1 Essentials in Paediatric Clinical Research
There are key elements where most scientists will agree are necessary in drug
development if children are to be considered as integral part of it. Among other
things, an assessment must be performed for each disease which delineates unmet
medical needs and ongoing efforts in basic and applied research (e.g. understand-
ing of disease processes, target identification). Another critical factor under-
pinning a more effective approach to paediatric drug research is the ability to
access and share data on disease, safety and treatment outcome across organi-
sations. Currently, regulatory authorities are the only stakeholders who have the
privilege to access, to review and to mine preclinical and clinical research data
across a wide range of diseases. It could be argued that such valuable data should
not remain obscure to the wider scientific community, that the benefits from
sharing disease and treatment-related information represent an opportunity to
every stakeholder, and that mechanisms could be implemented to protect com-
mercial and patent interests without dismissing the impact that further integra-
tion of information can have on therapeutics. This discussion will go on for a
long time.
Concerted efforts are also required to ensure optimal implementation of clini-
cal development plans for each drug that reaches development stage. Unfortu-
nately, little attention has been paid so far to the implementation of paediatric
trials. The ethical, practical and financial burden associated with gathering evi-
dence from pharmacokinetics, efficacy and safety in children remains irrespective
of the therapeutic indication. In addition, lack of consensus exists in areas such as
(1) accepted age-matched normal range for laboratory measurements (e.g., for
haematology, biochemistry, urinanalysis), (2) requirements for the validation of
clinical endpoints for the assessment of efficacy and safety, and (3) standards for
long-term safety monitoring and pharmacovigilance. Moreover, guidelines and
policies for paediatric drug development are still highly regulated on a regional
base, despite the availability of a worldwide framework by ICH. Considerable
differences remain between regions and personal views seem to dictate imple-
mentation policies. In contrast, the decision regarding which therapeutic area to
invest is entirely up to local decision-makers usually from private companies.
Investment choices from non-profit organisations such as the Bill Gates founda-
tion (USA) or governmental institutes such as Institute Pasteur (France) and
Fiocruz Institute (Brazil) are minority examples of a different modus operandi
in R&D. Despite evidence for effective results, they have not had the impact on
market drivers which individual companies have had so far. Channelling the
debate on unmet medical needs and on the requirements for the level of evidence
through non-profit organisations may represent an opportunity to further find
common ground between private interests (patient advocacy groups, pharmaceu-
tical companies) and public health policies.
The future of paediatric development will ultimately depend on decision-
makers. However, fundamental modifications are required in the way decisions
are made about medicines for children. One thinkable scenario would be a joint
international governmental programme to reimburse new drugs with proven clini-
cal benefit based on health outcome, comparable to the approach that has evolved
over the last decades for vaccination and immunisation programmes across the
world. Various rare diseases and therapeutic niches exist which would benefit from
a similar framework. Entrepreneurial efforts could lead to start-up companies
which can rely on return of investment. This mechanism would trigger oppor-
tunities for identifying investors and clinical development venture capital. New
charities and research organisations with clear focus might evolve. In this
public–private partnership paradigm, profit margins can be defined by consensus
of all relevant stakeholders, rather than by shareholders.
4 Incentives and Rewards
Irrespective of a shift in the paradigm for sponsorship and prioritisation of diseases,

the need for incentives and rewards in paediatric drug development will remain.
The use of incentives has been the primary mechanism in the United States and
more recently in the European Union. This type of reward, based on extension of
patent protection, has triggered numerous paediatric development programmes for
drugs which are still under protection. Through these programmes, children are now
already more exposed to clinical research than they have ever been in the past. The
key mechanism is the offer to pharmaceutical companies to prolong the duration of
patent protection against generic competition for a limited time. In return, the
originating company negotiates a paediatric development plan with the authorities.
It is important to realise that patent protection is prolonged for the all marketed
indications, i.e. adults and children. One could argue that adults have to pay for
paediatric research – but what is wrong about that? Children cannot pay for
themselves.
Incentivising paediatric research through patent extension or market exclusivity
can only work under several conditions. Firstly, there must be competition with
generic drugs and a third-party payer system. This first set of requirements exists in
the United States and Europe, but much less in Japan and other markets. Therefore,
the road to a comparable approach in other areas of the world is blocked. Other
strategies must be contemplated there. Secondly, the respective market for which a
patent extension is granted needs to have a critical mass that makes the added value
of a patent extension large enough to trigger investments in paediatric research.
Despite the population size of emerging market countries such as India, China and
Brazil, at present these markets are not sufficiently large to offer serious incentives
for paediatric research. Thirdly, the mechanisms underlying patent protection
must be strong and sufficiently robust to prevent infringements. Again, the quoted
countries are examples of emerging economies where patent protection mech-
anisms are still weak. In addition, current public health policies are aimed at
providing the population with those drugs that cover the medical needs of the
majority. As a result, few R&D companies based in these countries have been
able to develop innovative medicines.
Incentivising paediatric research for innovative drugs has so far produced very
limited incentives for older, off-patent drugs, most of which continue to be used in
an empirically, off-licence manner. The U.S. government had promised to pro-
mote clinical investigations on off-patent drugs but for years did not provide the
necessary funds. This situation has now started to change, and impressive NIH-
guided development programme are under way now to scrutinise the use of
many off-patent drugs in the paediatric population. A similar initiative has been
implemented in the EU under the auspices of the Research Directorate, which
allocates research grants on therapeutic areas, which have been identified as
unmet medical needs.
5 A New Role for Regulatory Authorities
A few decades ago, it was unthinkable to envisage Western governments enforcing

choices to pharmaceutical industry regarding which drugs should be developed for
children. This has however evolved: the incentives of the paediatric legislation have
to some degree influenced the directions industry pursues. The requirement for a
paediatric investigational plan (PIP) to be submitted to the European Medicines
Agency at an early stage of development is enforcing disclosure of key information,
including planned therapeutic targets and indications for compounds in develop-
ment. Even though at an early stage a company may not be certain whether the
compound will ever become a marketed drug, this process enables regulators to
scrutinise how efforts and resources are being allocated to drug targets and diseases.
It is also prompting a dialogue on the contents of the paediatric programme, with
direct impact on the level of evidence required for approval and consequently to the
rewards. Indirectly, regulators have also got the opportunity to impose waivers on
areas deemed unnecessary or low priority.
Nevertheless, as indicated previously, the majority of the off-patent drugs
licensed for an adult indication continue to be used without scientific evidence
for the dose rationale, benefits and risks in children. A different funding model
is required to prioritise evaluation of these drugs. In this context, it is clear that
regulation can play an important role in shaping the future of paediatric drug
development. One should not, however, consider regulatory mechanisms as the
only means to promote the advancements in the field. Incentives and regulatory
requirements have to be seen in a much wider context. And there will always
remain national and geographical borders.
6 Strategy for a Paediatric Development Plan
One of the main changes in the way drugs have been approved for paediatric use is
the requirement for formal evidence of efficacy and safety as needed for adult
indications. Historically, the implementation of paediatric legislation in the United
States from 1997 to 2007 [FDA Modernization Act (FDAMA), Pediatric Research
Equity Act (PREA), Best Pharmaceuticals for Children Act (BPCA), FDA Amend-
ment Acts (FDAAA)] (2010) has driven paediatric product development without
explicit timing for the generation of such evidence. The absence of a milestone for
the implementation of paediatric plans has caused a major gap in R&D. Given that
most clinical studies were phase IV commitments, poor integration of the clinical
plans has become common practice for indications which include adults and
children. Despite the controversy, this system has improved the off-label use of
most licensed medicines.
The introduction of the paediatric legislation in the EU has added an important
element to paediatric research. It defines the timing at which a paediatric plan
should be in place. The regulation has changed the R&D landscape by introducing a
milestone for the implementation of a proposal, the paediatric investigational plan,
which could even occur in parallel to the development of the adult indication, where
applicable.
A detailed description of the requirements for a paediatric development plan is
out of the scope of this chapter, but the new EU legislation is triggering a profound
review of strategy and key processes in adult and paediatric drug development.
There are various challenges from a clinical and scientific perspective, including
establishing the rationale for dose selection in clinical trials in children, identifica-
tion and validation of primary endpoints for paediatric diseases and the assessment
of long-term safety in paediatric trials. From a theoretical perspective, one impor-
tant challenge is how to distinguish the influence of developmental growth and
other external factors from drug-related effects. Of particular interest is the role of
co-morbidities specific to childhood which may become important confounders
of drug response in children. On the other hand, the shift in paradigm also poses a
challenge to clinical practice, which will have to abandon informal, off-label
prescription as the basis of therapeutic innovation. Paediatricians and clinical
researchers have to face the requirements for the generation of formal evidence.
This is and may remain a major cultural hurdle throughout the next generation.
Paediatric prescription has been dominated by empiricism and myths about how to
best treat children. This problem is compounded by the lack of scientific and
technical training in paediatric clinical pharmacology, which would provide
paediatricians with the appropriate set of skills to design better trials and accurately
interpret findings from randomised clinical trials.
As indicated above, for the first time in the history of paediatric medicine, the
assessment of risk–benefit ratio is becoming a prospective exercise. The dialogue
between industry, academia, professional networks, regulators and patient organi-
sations will be critical to ensure paediatric needs are prioritised and complexities
understood accordingly.
Conceptually, the development of a paediatric strategy must account for a
number of aspects, which can be categorised as follows:
1. Level of evidence. Arguments to support the need to generate efficacy data vs.
using indirect inferences from extrapolation and bridging studies.
2. Disease. Understanding of differences or similarities in aetiology, epidemiol-
ogy, symptoms and signs across populations. This includes the availability of
common endpoints for the assessment of efficacy and safety in children of
different ages vs. adults.
3. Dosing rationale. Understanding of the requirements for the dosing rationale
which should be based on exposure–response relationships, rather than empiri-
cally defined by differences in body size. These considerations apply equally to
efficacy and safety.
4. Drug delivery. Understanding of the implications of changes in dosage form
and route of administration, taking into account the need for age-suitable
formulations.
5. Study implementation. Major differences exist in terms of population size,

patient stratification, sampling frequency, statistical design, which are required
to generate evidence in children. Innovative designs can be used in conjunction
with pharmacostatistical methods that enable assessment of pharmacokinetics,
efficacy and safety. The use of placebo-controlled parallel group designs is by
far the most used method and the least desirable design in children.
6. Risk management. Long-term safety and risk management of paediatric products
can differ considerably from adult indications. The ability to distinguish the
influence from developmental growth and other age-related factors from intrin-
sic drug effects is critical for establishing preventive actions and assessing drug-
relatedness.
These points represent a pragmatic view of the principles defined by the ICH E11
and should form the basis for a global strategy. Clinical researchers, paediatricians
and regulators have been aware of these needs for a long time, but very few experts are
knowledgeable about how to properly evaluate drug use in the intended population.
It is worth mentioning that the data to support the use of a paediatric formulation
and the information required to define the dosing rationale may not be trivial and
will often require close integration of the knowledge from the development
programme for the adult indication. These two items will influence the timing,
contents and cost of all subsequent actions to generate evidence on pharmacokinet-
ics, efficacy and safety data. The development of formulations and assessment of
corresponding bioavailability and bioequivalence will often rely on data from adult
(healthy) subjects. The information required to characterise pharmacokinetic-
pharmacodynamic (PKPD) relationships and scale doses across populations will
also depend upon the availability of a well-designed clinical plan in adults. Lastly,
the use of juvenile toxicology studies must be linked to further understanding
of biomarkers, disease and species differences. Inaccurate interpretation of such
findings may jeopardise the selection of the appropriate dosing regimen and sub-
sequently lead to failure of the programme.
7 Limitations of Paediatric Legislation
The paediatric legislation alone is unlikely to change the directions of paediatric

research, discovery and drug development. As long as pharmaceutical R&D
remains dependent upon economical drivers, individual organisations will not be
able to make decisions regarding what to develop or not based primarily on value
proposition for patients. In fact, those who choose for a different strategy may not
survive. Furthermore, the recent approval by the United States of new health care
legislation indicates that health care systems are changing even in areas of strong-
hold of free market. Access to and reimbursement of pharmaceuticals and
biologicals are part of a much wider network, and as such cannot be evaluated in
isolation. Of particular importance is the impact of ageing in Western countries and
the increasing need to address chronic degenerative diseases.
Another shortcoming in the current regulation is the extent to which it is

applicable. Whilst gathering of formal evidence for the efficacy and safety is
undisputable, the need to consider a paediatric investigational plan for every new
formulation, route of administration or dosage form creates a potential for an
excessive number of paediatric clinical trials. This is aggravated by the lack of a
procedure to objectively evaluate medical need and by the limited experience of the
PDCO [Paediatric Committee] members in drug development.
Despite these limitations, the legislation in the United States and European
Union has the merit of ensuring that children are considered as an integral part of
the R&D process. Such a strict path has never been created for other special patient
populations.
8 Future Perspectives in Regulatory Affairs and Public

Health Policies
The paediatric legislation in force in both the United States and European Union has
and will have long-lasting implications for the development of medicines for
children. Paediatric legislation will evolve further and will certainly not cease
to exist in either region. They have introduced processes and procedures which
will become an integral part of the drug development pursuit. Companies and
organisations that dismiss this shift in paradigm will have to face penalties imposed
not only by regulatory authorities on the file-ability of a market authorisation
application, but also by the resulting change in medical culture and market percep-
tion, which will disfavour off-label use of medicines in children. Most importantly,
this change may have consequences to the liability of sponsors and paediatricians to
legal action.
It is also important to consider that public understanding of drug development is
limited at present. Some facts are well known, e.g. increased life expectancy in
Western countries and the role modern pharmaceutical treatment plays in this.
Other facts remain unclear, particularly in Europe. There remains a quasi-mystical
belief in the medical wisdom and in the role of medical training. The appreciation
of the value of clinical trials as a key pillar of therapeutics is much less established.
This is exacerbated by media speculation and by the belief that children should not
be the subject of clinical experimentation. In general terms, this attitude reflects
cultural and historical differences between nations. U.S. citizens, on the other hand,
have a stronger scepticism towards authority and are more prepared to tread new
paths. Irrespective of these differences, the importance of gathering evidence on
efficacy and safety based on controlled, randomised clinical trials will become
obvious to parents, society and to many other stakeholders.
The debate will go on with defenders and contenders of governmental con-
trol and of entrepreneurial freedom. Albeit difficult to predict what will happen
in detail, regulatory authorities become active players in drug development. Regu-

latory authorities have triggered processes and requirements for demonstrating
efficacy and safety. Together with all other stakeholders, they share the responsi-
bility for the advancement of health care. Their defensive or conservative role has
influenced drug development in different directions. From the availability of anti-
retroviral drugs for HIV to the recent approval of HIN51 flu vaccine, regulators
have represented the hurdle or the thrust for patient access to innovative therapeutic
options.
9 Foreseeable and Unforeseeable Developments
Personalised medicine is still an evolving concept, which demands a very different

approach to diagnosis, therapeutics and prognosis of diseases in adults and children.
This is taking place in parallel with the evolution of health technology, which has
established criteria for ranking effectiveness and consequently for reimbursement
policies. Drug discovery, development, approval and labelling will have to account
for the requirements this advancement entails. Moreover, the definition of disease,
dysfunction and disorder are also changing. New phenotypes are being identified
and increasingly more, rare diseases are described, most of which occur in children.
As long as health care institutions can afford the cost of innovation in the diagno-
sis, treatment and prophylaxis of (new) diseases, it can be anticipated that R&D
organisations will prioritise investments for the development of therapeutic agents
for rare conditions.
In this landscape, it is likely that new specialised niche companies will arise as
suppliers of expertise and technology. Development organisations will become
distinct from discovery organisations, with the objective of not only launching
new products into the market, but also of ensuring clear value proposition and
reimbursement of new treatments. Unfortunately, the incentives for innovation also
represent a risk to the optimisation of the therapeutic use of existing, off-patent
drugs. Despite the possibility of up to 10-year data protection in exchange for
paediatric development in the European Union, it is unlikely that new label
recommendations, or novel paediatric formulations will rank sufficiently high to
ensure reimbursement against other therapeutic options (e.g. generics).
It is not possible to predict with accuracy to what extent the ongoing tech-
nology revolution will translate into immediate changes in health care. For the
moment, it is clear that society will have to face the consequences of the
developments and changes in society and lifestyle over the last 50 years. A further
wave of child obesity with all ensuing sequelae, including hypertension, diabetes,
dyslipidaemia and other potential health issues will most likely be the focus of
attention.
10 Conclusions
Drug development is not a linear process which can be easily directed by guide-
lines and policies. It involves numerous, complex iterations, many of which do
not depend solely on logical, scientific judgement or criteria. It also depends on
medical, economical, ethical and political considerations. Given the nature of the
latter factors, consensus in health care priorities, medical needs and reimbursement
will remain an additional challenge for all stakeholders in R&D. Society, and in
particular children and adolescents, will continue to develop and behave differently
from today. They will face other lifestyle challenges and will have access to
different therapeutic options than today’s generation. In any case, the current
regulatory framework shows that legislation will continue to determine or at least
influence the directions and future of public health care. The right of access to safe
and effective medicines is certainly an achievement which cannot be overturned.
References
Cella M, Knibbe C, Danhof M, Della Pasqua O (2010) What is the right dose for children?
Br J Clin Pharmacol 70:597–603. doi:10.1111/j.1365-2125.2009.03591.x
DNDi (Drugs for Neglected Diseases Initiative) (2010) http://www.dndi.org. Accessed 14 Oct
2010
European Medicines Agency (2010) http://www.ema.europa.eu. Accessed 14 Oct 2010
FDA (Food and Drug Administration) (2010) http://www.fda.gov. Accessed 14 Oct 2010
FDAAA (FDA Amendment Acts) (2010) http://www.fda.gov/RegulatoryInformation/Legislation/
FederalFoodDrugandCosmeticActFDCAct/SignificantAmendmentstotheFDCAct/
FoodandDrugAdministrationAmendmentsActof2007/default.htm. Accessed 14 Oct 2010
Gates Foundation (2010) http://www.gatesfoundation.org. Accessed 14 Oct 2010
Hilts PJ (2003) Protecting America’s health. Alfred A. Knopf, New York
ICH (2010) International Conference on Harmonisation of technical requirements for registration
of pharmaceuticals for human use. http://www.ich.org. Accessed 14 Oct 2010
ICH E11 (2010) ICH tripartite guideline: clinical investigation of medicinal products in the
pediatric population. http://www.ich.org/LOB/media/MEDIA487.pdf. Accessed 14 Oct 2010
MMV (Medicines for Malaria Venture) (2010) http://www.mmv.org. Accessed 14 Oct 2010
Rose K, van den Anker J (eds) (2010) Guide to paediatric drug development and clinical research.
Karger, Basel, Switzerland, http://content.karger.com/ProdukteDB/produkte.asp?Aktion¼
showproducts&searchWhat¼books&ProduktNr¼253804. Accessed 14 Oct 2010. ISBN 978-
3-8055-9362-5; e-ISBN: 978-3-8055-9363-2
Stoetter H (2007) Paediatric drug development: historical background of regulatory initiatives. In:
Rose K, van den Anker JN (eds) Guide to paediatric clinical research. Karger, Basel, pp 25–32
Taussig HB (1962) A study of the German outbreak of phocomelia. JAMA 180(32):1106–1114
Wax P (1995) Elixirs, diluents, and the passage of the 1938 Federal Food, Drug and Cosmetic Act.
Ann Intern Med 122:456–461
WHO (2010) http://www.who.int. Accessed 14 Oct 2010
Study Design and Simulation Approach
Stephanie L€
aer and Bernd Meibohm
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126
2 Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
2.1 Computer-Based Modeling and Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127
2.2 Models for Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129
2.3 Clinical Trial Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
2.4 Virtual World Simulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137
3 Improving Dosing Strategies by Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 138
3.1 Examples of “Top Down” Simulations for Deriving Dosing Recommendations . . 138
3.2 Examples of “Bottom Up” Simulations for Deriving Dosing Recommendations . 141
4 Improving Clinical Trial Design by Simulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
4.1 Fastening Timelines of Clinical Trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 144
4.2 Optimizing Sample Size and Selection of Pharmacokinetic Sampling Time
Points for Pediatric Trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
5 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 147
Abstract Modeling and simulation techniques are a mainstay of clinical drug

development and are particularly useful to support clinical trials in children. If a
pediatrician wants to use these tools most efficiently, a basic understanding of the
principles and methods of classical and novel techniques of modeling and simula-
tion is essential. Key elements comprise the definition and description of terms like
deterministic simulation, Monte Carlo simulation, classical “top down” or novel
S. L€aer (*)
Department of Clinical Pharmacy and Pharmacotherapy, Heinrich-Heine-University of
D€usseldorf, Universit€atsstrasse 1, 40225 D€
usseldorf, Germany
e-mail: stephanie.laeer@uni-duesseldorf.de
B. Meibohm
College of Pharmacy, University of Tennessee Health Science Center, 874 Union Avenue, Rm. 5p,
Memphis, TN 38163, USA

126 S. L€aer and B. Meibohm
“bottom up” approach, as well as the term “virtual world simulation.” The
illustrated examples in this chapter from pediatric clinical trials will help to
understand and demonstrate these key elements. The importance of the understand-
ing of developmental physiology and pharmacokinetics will become visible when
explaining novel “bottom up” approaches like physiologically based pharmacoki-
netic simulations which also bridge to current research tools from other areas such
as systems biology using mathematical models to describe biological systems.
Keywords Modeling • Simulation • Top-down • Bottom-up • Children
Abbreviations
BSA Body surface area

CO Cardiac output
CYP Cytochrome P450
fu Unbound fraction of a drug
GFR Glomerular filtration rate
Ka Acid constant
Km Michaelis–Menten constant
LogP Parameter describing lipophilicity of a drug
LOQ Limit of quantification
M&S Modeling and simulation
MM Michaelis–Menten
Mwt Molecular weight
PBPK Physiology-based pharmacokinetics
PD Pharmacodynamic
PK Pharmacokinetic
QH Total hepatic blood flow
QT interval Section of track of the electrocardiogram
QTc interval Section of track of the electrocardiogram corrected for heart rate
t1/2 Terminal half life
UGT UDP-glucuronyltransferases
USA United States of America
Vd Volume of distribution
Vmax The maximum initial velocity or rate of a reaction
1 Introduction
Modeling and simulation techniques are a mainstay of clinical drug development

for adults and children. European and international guidelines for the development
of medicinal products refer to these techniques. Model-based methods are particu-
larly useful to support pediatric drug development because they provide means to
Study Design and Simulation Approach 127
leverage knowledge from adult clinical trials enabling efficient data collection by
providing dosing schedules, optimizing and/or minimizing the number of plasma
samples required for pharmacokinetic and pharmacodynamic investigations and
even minimizing the number of infants and children required in clinical trials.
In this chapter, the principles and methods of modeling and simulation
approaches using computers and computer software are explained. The illustrated
examples from pediatric clinical trials should help to understand and demonstrate
the key elements of classical and novel modeling and simulation tools for pediatric
drug development. The specific topics will:
– define the terms deterministic simulation and Monte Carlo simulation.
– describe the classical “top down” and the novel “bottom up” approach of
modeling and simulation.
– describe virtual world simulation.
– provide a portfolio of examples of simulations to illustrate the benefits and
limitations of simulations.
2 Methods
2.1 Computer-Based Modeling and Simulation
In the healthcare environment, numerical simulation utilizes mathematical

abstractions of processes representative of isolated organs, tissues, whole body
organisms, populations of individuals as well as whole societies combined with
computing resources to address real-life medical problems.
Modeling and simulation are two techniques that are so closely related to each
other that they are usually mentioned in conjunction as a “modeling and simula-
tion” (M&S) approach. Modeling in this context usually comprises the description
of the behavior of a system or process by a set of mathematical expressions that is
usually a simplification of certain aspects of reality and focuses only on those
factors and processes that are believed to be important. Simulation is then the
application of this mathematical model usually over time to explore situations
that have not been investigated experimentally, thereby extrapolating beyond the
currently available experimental data (Laer et al. 2009).
In the context of pharmacotherapy, the M&S approach can be viewed as one of
the three pillars of facilitating the solution to pharmacotherapeutic problems, along
with theoretical reasoning and hypothesis building as well as clinical experimenta-
tion (Fig. 1). The M&S process visualizes and optimizes the clinical experiment and
thus helps fastening the process, utilizing resources including research subjects
more efficiently, and even reducing the number of experiments needed to be
performed. Thus, the M&S approach holds great promise especially in pediatric
drug development and applied pharmacotherapy, where the optimal and ethically
acceptable use of limited resources with regard to patients, measurements, and
Fig. 1 Modeling and simulation as one of the three pillars of facilitating the solution to
pharmacotherapeutic problems, along with theoretical reasoning and hypothesis building and
clinical experimentation. The modeling and simulation process visualizes and optimizes the
clinical experiment and thus helps fastening the process and even reducing the number of
experiments needed to be performed. From Laer et al. (2009)
interventions is even more pressing than in other areas of the healthcare

environment.
2.1.1 Deterministic Simulation
Classic approaches in pharmacokinetics and pharmacodynamics usually use deter-

ministic simulations to predict for example time courses of drug concentrations or
time courses of drug effect intensities. These deterministic simulations use parameter
point estimates for their simulations, which may be considered the “best guesses”
for specific parameter values. Thus, one set of parameters for a given model will
result in one discrete simulated outcome, for example, a discrete drug concentration
vs. time profile in response to a given dose or dosing regimen. The parameters
themselves may be dependent on patient specific covariates such as demographic,
anthropometric, physiologic or pathophysiologic variables, but each set of
parameters will simulate only one specific outcome.
Compartmental pharmacokinetic models applied for individual pediatric
patients with discrete data sets, for example, are classic examples of deterministic
simulations (Laer et al. 2001). For a given set of parameter point estimates and a
specific dose/dosing regimen, they result in one discrete time profile of simulated
concentrations. The major advantage of this approach is simplicity and ease of
understanding, especially for healthcare professionals not familiar with M&S
techniques. A major limitation, however, is the fact that parameter point estimates
are given absolute credibility without appreciation of uncertainty related to the
estimation process through which they were derived. In addition, only a limited
number of patient-specific covariates predictive of drug disposition or response are
usually known, and thus patients with even similar known covariates will exhibit a
distribution of different parameters, which will subsequently result in variability in
drug exposure and/or response. The deterministic modeling approach neglects this
uncertainty of the parameter point estimates.
2.1.2 Monte Carlo Simulation
In contrast to deterministic simulations, Monte Carlo simulations are a stochastic

simulation technique. Rather than relying on fixed parameter point estimates,
Monte Carlo simulations rely upon distributions for each specific parameter that
capture the degree of uncertainty in each parameter. Each distribution is defined by
a central tendency (e.g., mean or median) and a spread or variability term (e.g.,
variance or standard deviation). Monte Carlo simulations then use repeated random
sampling of parameters from these distributions to simulate the outcome based on
the underlying structural model. Thus, Monte Carlo simulations do not result in a
discrete outcome, for example, a concentration-time or response-time profile, but in
a distribution of outcomes for which again a central tendency (e.g., mean or
median) and a distribution (e.g., 90% confidence interval) can be defined
(El-Tahtawy et al. 2006). As such, Monte Carlo simulations have the advantage
to provide inherently a measure of credibility and likelihood for simulation
outcomes that is usually lacking in discrete simulations. A major disadvantage,
however, is the increased complexity of the analysis and thus the difficulty in
acceptance and understanding of the derived simulations by healthcare
professionals not familiar with M&S techniques.
2.2 Models for Simulation
2.2.1 “Top Down” Approach
Modeling approaches in drug development can in general be differentiated into

deductive and inductive approaches. Deductive approaches, often also referred to as
“top-down” or “analytic” approaches, are based on generalized concepts in medical
sciences such as clinical pharmacology. They can be seen as a verification-driven
data mining process that allows a modeller to express preconceived facts or theories
in model terms, subsequently test their validity within the context of the model
system and the available data, and obtain reasons for the validation or invalidation.
Thus, the deductive model development process is characterized by a constant
rebuilding and refinement of the model given the results of the continuous hypoth-
esis testing. As such, “top-down” modeling is clearly a data-driven process, in
which the model is iteratively refined to optimally describe observed data (Laer
et al. 2009).
Compartmental pharmacokinetic modeling or the Emax-model as a frequently

used pharmacodynamic model are clearly empirical models that are derived
through the “top down” process and are oftentimes iteratively refined during the
model building process through hypothesis testing by evaluation via statistical
means whether a modification in the model is actually reflected in an appropriate
improved model fit. Albeit largely empirical, “top down” models can still include
mechanistic or semi-mechanistic structural model components related to a drug’s
known pharmacologic mechanism of action and its interplay with physiologic
systems.
In pediatric clinical pharmacology, population pharmacokinetic (PK) and popu-
lation pharmacokinetic/pharmacodynamic (PK/PD) analyses are frequently applied
to identify significant determinants of drug disposition and response, and derive and
optimize dosing regimens in drug development and applied pharmacotherapy
(Bartelink et al. 2006; Meibohm et al. 2005). Population PK/PD analyses are
typically performed following a “top down” approach. A population PK/PD
model consists of a structural, a stochastic, and a covariate model component. In
a first model building step, different structural models, for example. compartmental
pharmacokinetic models, are explored in their ability to describe the observed data.
Review of goodness-of-fit criteria in visual or numeric form as well as evaluation of
statistical summary criteria allows the selection of the most appropriate structural
model alternative. In a second step, parameter and error distributions are added in a
stochastic model component to differentiate among between-subject variability,
between-occasion variability, and unexplained residual variability. In a third step,
patient covariates are explored in their ability to predict a fraction of the between-
subject variability (Sheiner and Ludden 1992). Thus, the model is sequentially
refined using reiterative hypothesis testing, thereby providing a final model that is
based on general clinical pharmacology principles and additional details derived
from the structure of the available data set.
2.2.2 “Bottom Up” Approach (Physiologically Based Pharmacokinetic

Simulation)
In contrast to deductive approaches, inductive modeling approaches, also called

“bottom-up” or “synthetic” approaches, synthesize specific available observations,
data, and patterns to form broader generalizations and theories. In this modeling
approach, individual elements are linked together to form larger subsystems, which
then in turn are linked, sometimes in many levels, until a complete top-level model
is formed. Physiologically based pharmacokinetic (PBPK) modeling can be seen as
an example of inductive modeling. While the “top-down” approach (e.g., via a
population pharmacokinetic analysis) aims to partition variation in pharmacokinet-
ics via measured covariates (demographics, biomarker, etc.), the “bottom-up”
approach focuses on constructed simulation models consistent with physiologic
parameterization of pediatric populations and drug-specific parameters (Khalil and
Laer 2011; Willmann et al. 2003).
Concept of Physiologically Based Pharmacokinetic Modeling
The general idea of PBPK modeling is to mathematically describe all physico-

chemical and physiological processes that are involved in the determination of
substance pharmacokinetics in as much detail as possible. To do this, knowledge in
physiology and anatomy will be used to represent the species to be modeled (e.g.,
human body) or part of it (in case of systems simulation) as a structure composed of
physiologically relevant compartments, where each compartment usually
represents a single organ or tissue. These compartments will be interconnected,
following the anatomical structure of the organism, via the blood circulation loop.
Then, mass-balance equations for each compartment describing the fate of the
substance within it will be established.
Information for the PBPK model about the different physiological parameters
such as organs/tissues/fluids weights and volumes, cardiac output, regional and
tissue blood flows, surface area will be obtained from the literature. To make the
model complete, the compound-specific parameters are incorporated. These are not
static and vary according to the substance under study, most importantly perme-
ability and partitioning of the substance between body tissues and the blood/plasma.
Tissue/plasma partition coefficients can be obtained either from in vitro
experiments, by extrapolating the experimental partition coefficients values from
animals to humans, or by calculation/prediction from tissue composition (lipids,
proteins, water) and physicochemical properties of the substance in interest. These
include molecular weight (Mwt), lipophilicity (mostly in term of LogP value), acid
dissociation constant (pKa), solubility, blood to plasma concentration ratio and
affinity to albumin [in terms of fraction unbound (fu)].
At the end, the PBPK model employs all these information in order to describe
and/or predict the pharmacokinetics of a drug in certain individuals. However,
PBPK models can vary in their complexity from simple (basic) to advanced
(complex) depending on the model purpose and can range from partial-body
models, where only certain systems are included, to whole-body models, where
all the important organs and tissues are included. Because some specialized PBPK
model software (e.g., PK-Sim®) has additional incorporated modules such as
scaling clearance from adults to children and a population pharmacokinetic module,
which extend its function and use, these are of importance in the simulation of
pharmacokinetics for children. A representative schematic drawing illustrates this
concept (Fig. 2 modified from Willmann et al. 2003).
Physiology-Based Pharmacokinetic Modeling in Children
For the integration of physiological data occurring in childhood, age-dependent

processes of organs, blood flow, and biochemical processes are incorporated from
databases or represented by a variety of regression functions in the PBPK models.
These include physiological characteristics of organs, tissues, and blood flows as
described by Johnson et al. (2006) (Table 1, Fig. 3 modified from Johnson et al.
a b
c d PLASMA LUNG
10 10
1 1
0.1 0.1
0.01 0.01
10 10
LIVER KIDNEY
1 1
0.1 0.1
0.01 0.01
10
Concentration [µg/ml]
10 MUSCLE BONE
1 1
0.1 0.1
0.01 0.01
10 10
SKIN FAT
1 1
0.1 0.1
0.01 0.01
1 10
BRAIN TESTES
0.1 1
0.01 0.1
0.001 0.01
0 2 4 6 8 10 0 2 4 6 8 10
Time [h]
Fig. 2 Illustration of the concept for building a physiologically based pharmacokinetic model
modified according to Willmann et al. (2003). (a) Organisms, e.g., human beings of different ages
or populations are the basis for the model. (b) The organism is divided into a number of
compartments, each representing a single organ. To describe the distribution of compounds in
the body the organs are connected via their arteries and veins to the arterial and venous blood pool.
Inter-compartmental mass transport occurs via organ-specific blood flow rates. The organs are
mathematically connected. (c) Division of each organ into three sub-compartments representing
the vascular (with blood cells), interstitial, and cellular space. The interstitial space is assumed to
be in direct contact with the plasma. The exchange of substances between the cellular and
interstitial compartment can occur by permeation across the membranes via passive diffusion as
well as active influx and efflux transport processes by saturable Michaelis–Menten (MM) kinetics
(parameters: Vmax, Km). Metabolization of substances (Meta1, Meta2) occurs via active enzymes
(MM-kinetics). Finally, the model consists of a large number of coupled differential equations. (d)
Output of the model: Concentration time curves for the substances. Shown are simulated and
observed ciprofloxacin concentrations in various organs after intravenously applied ciprofloxacin
5 mg/kg to a rat
Table 1 Body and tissue weights (kg), cardiac output (L/min) as function of age according to
Bj€orkman (2004)
Tissue Neonate 6 months 1 year 2 years 5 years 10 years 15 years Adult
Body 3.55 8.03 10.2 12.6 19.7 31.4 56.7 73.0
Lung 0.06 0.12 0.16 0.24 0.34 0.43 0.90 1.20
Liver 0.12 0.27 0.36 0.48 0.59 0.87 1.35 1.80
Kidney 0.03 0.05 0.06 0.09 0.11 0.18 0.25 0.31
Gut 0.05 0.09 0.14 0.19 0.34 0.58 0.82 1.02
Muscle 0.80 1.35 1.90 2.83 5.60 11.0 24.0 29.0
Adipose 0.89 2.97 3.64 3.76 5.0 7.50 9.50 14.5
CO 0.58 1.35 1.68 2.06 2.88 3.90 5.77 6.79
QH 0.22 0.38 0.45 0.53 0.72 1.04 1.55 1.72
CO cardiac output, QH total hepatic blood flow
Fig. 3 Changes in liver volume (LV) (a) and liver blood flow (b) as function of age according to
Johnson et al. (2006)
2006), the fraction of vascular and interstitial space, changes in total body water and
adipose tissue content, plasma protein concentration especially of albumin and
alpha glycoprotein, and renal and hepatic elimination.
There are numerous reports about developmental changes in metabolizing
enzymes from birth to adolescence (van der Marel et al. 2003; Bouwmeester
et al. 2004; see also Table 2). Nearly each CYP450 isoform shows a different pattern
of maturation, and might influence the drug clearance with respect to specific age
Table 2 Enzyme activities (expressed as fraction of adult values) as function of age Edginton
et al. (2006)
Enzyme Neonate 1 month 3 months 6 months 1 years 10 years
Cyp3A4 0.24 0.5 0.7 1.1 1.3 1
Cyp1A2 0.1 0.2 0.25 0.29 0.35 1
Cyp2E1 0.32 0.4 0.46 0.46 1 1
UGT2B7 0.064 0.1 0.3 0.7 1 1
groups. The most abundant hepatic CYP450, the CYPs 3A4 and 3A7, which belong
to the subfamily CYP3A, show a different evolution with time: CYP3A7 is the
major active isoform in neonates and young infants but there is a progressive shift
from CYP3A7 toward CYP3A4 in the first weeks of life. And, although these
enzymes share at least 85% sequence identity, they exhibit large differences in
substrate specificity and catalytic activities (Hines 2008).
Similar to enzyme systems, the integration of the maturation of renal excretion
in a PBPK model is highly relevant because of its impact on the pharmacokinetics
of compounds with renal clearance as major elimination pathway (Alcorn and
McNamara 2003; Morselli et al. 1980; Yared and Ichikara 1994). Both, glomerular
filtration rate and tubular secretion, undergo developmental changes (Arant 1978).
Glomerular filtration rate increases rapidly in the first weeks to reach adult values
between 2 and 6 months because of an increase in cardiac blood flow, a decrease in
arteriolar resistance and an increase in the surface area and the pore size of the
glomerular membrane. The tubular secretion increases at a slower rate than the
glomerular filtration rate (GFR), particularly because of the delay in the maturation
of active transporters, but also due to the smaller size of the tubulus and a smaller
mass of functioning tubular cells in children. The maturation of tubular secretion
takes about 1 year.
PBPK Modeling Methodologies and Software
Several commercial software tools for the development of physiologically based

pharmacokinetic models are available on the market. It is important to distinguish
between general mathematical and engineering modeling software packages, and
specialized PBPK modeling software packages. General modeling software
packages, such as MATLAB®, ModelMaker®, Berkeley Madonna™, and
ACSL®, provide a programming language for the model code, routines to solve
the differential equations with differential equations integrator and a graphical
output of the simulation results. This software offers the greatest flexibility to the
PBPK model developer. Easier to use, however, are specialized PBPK modeling
software packages. They provide either a click-and-drag assembly of the model
structure or have already built one and require less mathematical background and
modeling experience. These can either simulate particular PK-relevant processes
(e.g., intestinal absorption or metabolic processes) or constitute generic whole
body PBPK models. Examples for such software are PK-Sim®, Simcyp®, and
GastroPlus™. Nevertheless, the use of PBPK modeling software relies on expert

knowledge in pharmacokinetics, physiological, pathophysiological, and develop-
mental pharmacological processes as well as sufficient experience in the develop-
ment of pharmacokinetic models using modeling software.
Implementations of PBPK Modeling
Through their enhanced ability to integrate relevant information (physiologically

relevant, substance dependent) generated from various sources, PBPK models have
gained attention in the fields of pharmacology and drug development and are more
and more competitive to empirical pharmacokinetic models. The following list
provides some applications of PBPK modeling. Some examples for pediatric
applications are given under Section “Examples of ‘Bottom Up’ Simulations for
Deriving Dosing Recommendations”.
(a) PBPK modeling can be used to describe and/or predict drug pharmacokinetic
profiles through simulation of different dosing regimens, which allows the
evaluation and optimization of already established dosing-regimens.
(b) A PBPK model enables the quantification of the exposure in remote and/or
inaccessible compartments, such as brain or tumor tissues.
(c) A PBPK model can be used to describe the pharmacokinetics of small-molecule
compounds, but also for large proteins and even nano-particles.
(d) PBPK modeling is useful as a learning tool to gain more information about the
different processes that are involved in determining drug disposition in tissues
as well as the magnitude of the influence of separate parameters on drug
pharmacokinetic behavior.
(e) PBPK models are used to describe and/or predict drug pharmacokinetics under
different physiological and pharmacological conditions, e.g., in individuals
with diseases or altered physiology. The effects of aging, rest, and physical
efforts have been explored by PBPK modeling technique.
(f) In case of the pediatric population, PBPK is used to predict drug pharmacoki-
netics in children (prediction of volume of distribution, clearance values, etc.)
and thus may help in the selection of the first dose in different pediatric age
groups as illustrated in Fig. 4 with an example for sildenafil (Hsien 2010). This
helps to provide information for conducting pediatric clinical trials in optimized
form (Fig. 4). PBPK modeling allows the suggestion of a first dose as well as
efficient sampling times, giving the opportunity of reducing the number of
children required for the clinical study.
Limitations of Physiology-Based Pharmacokinetic Modeling
PBPK modeling requires comprehensive data on the physico-chemical, physiolog-

ical, and biochemical processes of the organism and the drug. In case of PBPK for
a
Total clearance
12 Contribution of CYP3A4
Contribution of CYP2C9
10
Predicted clearance
(ml/min/kg)
0
0 2 4 6 8 10 12 14 16 18
Age (years)
b
dose mg/kg
0.5
(ng •h/ml)
2000
1500
0−∞
Simulated AUC
1000
500
0
0.25 0.5 0.75 1 1.5 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 Adults
Age (year)
Fig. 4 Simulation results of a PBPK model for sildenafil for children using the PK-Sim®.software
module (Hsien 2010). (a) Predicted age-dependent sildenafil hepatic clearance across the different
pediatric ages based on the clearance scaling module in PK-Sim®. (b) Age-related doses for oral
sildenafil in children depending on the simulated age-related exposure (not shown) of sildenafil in
a virtual pediatric population and the estimated exposure of the estimated doses of sildenafil in
children between 3 months and 18 years of age. Potential pediatric doses on the basis of the
simulations for sildenafil in order to achieve adult exposure: Infants and younger children from
3 months to 4 years: 0.8 mg/kg, children from 5 to 8 years 0.5 mg/kg and children older than
8 years 0.35 mg/kg similar than in adults. Box plots represent median, 25th and 75th percentiles
(box), 5th and 95th percentiles (error bar) and maximum and minimum values (x) of AUC
01 from 1,000 simulations in each age
children data on the ontogeny of these parameters are not always available and/or
they are not available from only one source. This may lead to some confusion and to
a problem in establishing a reliable source of accurate and consistent information.
In addition, some gaps may be present in fully or accurately describing some
physiological process especially in young children, which in turn may lead to an
inability of the model to successfully describe the pharmacokinetics of certain
drugs in this age group.
2.3 Clinical Trial Simulation
Clinical trial simulation is one of the more complex current applications of M&S
techniques and is an example that frequently combines model components derived
through inductive as well as deductive analysis approaches (Bonate 2000). Trial
simulation uses numerical simulation techniques to assess in silico how a clinical
study is likely to perform based on simulation of the behavior of its individual
participants and prior knowledge and assumptions for underlying distributions and
mechanisms (Girard 2005). As such, trial simulations may include a variety of sub-
models. It does not only include a structural dose–exposure–response/toxicity
relationship (PK/PD-model) that was derived using the “top-down” or “bottom-
up” approach, but also includes model components that capture access to patient
populations including patient demographics, study design, enrolment criteria,
natural progression of the disease, response to placebo, adherence to the
pharmacotherapeutic regimen, and drop-outs from the study. Each of these model
components contains one of multiple deterministic as well as stochastic elements.
With these model components, clinical trial simulation is able to run many virtual
repetitions of a trial. The multiple stochastic elements may affect trial outcome
differently in each repetition. With hundreds or thousands of virtual repetitions for
the trial execution, clinical trial simulation allows establishing a likelihood profile
of trial outcomes that provides the investigator information about the chance of
achieving the primary outcome of a study given a specific study design and trial
execution environment if only one real-life study is performed. Thus, clinical trial
simulation is an excellent tool to optimize study designs, especially in pediatric
populations where appropriate study populations are oftentimes scarce and study
performance is limited by ethical and logistical constraints. For this reason, the U.S.
Food and Drug Administration recommends to perform clinical trial simulation as a
routine approach to assess the appropriateness of trial designs in pediatric drug
development (Gobburu 2010).
2.4 Virtual World Simulation
An expansion of clinical trial simulations are so-called virtual world simulations. In

this approach virtual patients with discrete physiological and pathophysiological
characteristics are simulated in a virtual environment, where patient behavior,

access to healthcare, healthcare provider interventions, and lifestyle behavior are
all integrated. The Archimedes model is a prime example for virtual world
simulations (Schlessinger and Eddy 2002). This modeling approach integrates
human physiology, diseases, behaviors, interventions, and healthcare systems to
predict outcomes including quality of life for the individual patient, whole patient
groups with similar characteristics, as well as healthcare resource utilization and
healthcare costs. Hundreds of mathematical expressions are the core of the model
and represent human physiology and the effects of diseases relevant to the specific
condition. Attached to these are additional equations and algorithms that realisti-
cally simulate the healthcare system including processes such as tests, treatments,
admissions, and physician behaviors. Together with population data, the equations
are integrated into a single, large-scale simulation model that accurately represents
what happens to real people in real healthcare systems (http://www.archimedes.
com). The Archimedes model has been established for several chronic diseases,
including diabetes, cardiovascular disease and colon, breast and lung cancer. It is
utilized by healthcare providers and insurance organizations such as Kaiser
Permanente to assess the cost/benefit ratio of medical interventions. The American
Diabetes Association has adopted the Archimedes model as a risk assessment tool
for individual patients to assess the impact of lifestyle changes and healthcare
interventions (Eddy and Schlessinger 2003). It is freely accessible on
the association’s website under Diabetes PHD (personal health decisions) at
http://www.diabetes.org.
3 Improving Dosing Strategies by Simulations
3.1 Examples of “Top Down” Simulations for Deriving Dosing

Recommendations
3.1.1 Dosing Recommendations Based on Pharmacokinetic Simulations
The development of pediatric dosing recommendations based on the simulation of

plasma concentration-time profiles makes the assumption that the concentration–effect
relationship is independent of age and thus similar between children and adults. In
such a situation, dosing regimens that result in similar systemic exposure to the drug
should also result in similar efficacy. Antibiotics are a class of therapeutics for
which this assumption can often be made, as the concentration–effect relationship is
driven by the susceptibility of the pathogen to the antibiotic, especially if the
infection is localized in well-perfused tissues and the access of the drug to the
pathogen is not limited. In such a situation, variability in drug exposure in the host
is a major driving force for differences in efficacy.
Li and co-workers (Li et al. 2010) used this approach to derive dosing
recommendations for levofloxacin for the chemotherapy of postexposure
inhalational anthrax in children. As efficacy studies with inhalational anthrax are

ethically prohibitive, a population pharmacokinetic model for levofloxacin was
developed based on an adult data set (n ¼ 47) with concentration-time data after
a single dose of 500 or 750 mg/kg levofloxacin, given either intravenously or orally,
and a pediatric data set with 90 patients (0.5–16 years) receiving different intrave-
nously and oral dose levels. A covariate analysis identified body weight as signifi-
cant predictor for levofloxacin clearance and volume of distribution. In addition,
developmental changes in renal function in children under 2 years of age was a
major determinant of clearance as expected from the fact that renal excretion is a
major elimination pathway for levofloxacin with 70–80% excreted unchanged in
urine.
In subsequent simulation exercises, this population pharmacokinetic model was
used to explore different dosing approaches in children that would results into a
systemic exposure to levoflocacin similar to the daily dose of 500 mg approved for
this indication in adults. This exposure had been shown in animal experiments to
prevent the progression of pulmonary anthrax after inhalation exposure. These
simulations led to a recommended dose of 8 mg/kg twice a day for children
below 50 kg body weight, and 500 mg daily for children with a higher body weight.
3.1.2 Dosing Recommendations Based on PK and PD Simulations
If the pharmacodynamics or concentration–effect relationship for a therapeutic

agent is not constant with age, then developmental changes in pharmacokinetics
and pharmacodynamics have to be considered simultaneously to develop dosage
recommendations for pediatric patients. The development of dosage recommen-
dations for the antiarrhythmic drug sotalol for the treatment of supraventricular
tachycardia in children is an example where pharmacodynamic data for safety and
efficacy were combined with pharmacokinetic information to derive dosing recom-
mendations (Laer et al. 2005).
Based on pharmacokinetic data for sotalol in 76 pediatric patients between 1 day
and 17 years of age, including 12 neonates, 33 infants and toddlers, 26 children, and
5 adolescents, a population pharmacokinetic model was derived that identified
weight as significant predictor of clearance and volume, and age as a significant
additional predictor for clearance in neonates and infants younger than 1 year of
age. The latter was interpreted as the effect of maturation of glomerular filtration
and active tubular secretion during the first year of life, since sotalol is exclusively
eliminated by renal excretion. In a second step, the age-dependency of cardiac QT-
interval prolongation was assessed as safety biomarker. A population PK/PD
analysis in a subgroup of 32 pediatric patients revealed an age-dependency of the
slope for QT interval prolongation vs. sotalol plasma concentration, suggesting a
higher sensitivity toward QTc prolongation in neonates compared to older patient
groups. Finally, in a third step, a PD analysis was performed in 15 patients to
characterize the relationship between sotalol plasma concentration and conversion
into sinus rhythm as efficacy measure. The analysis predicted a 50% probability to
convert into sinus rhythm for a sotalol plasma concentration of 0.4 mg/ml, and a
more than 95% probability for 1.0 mg/ml, with no indication of an age-dependent
difference in antiarrhythmic efficacy.
All three analysis components were subsequently combined to derive dosing
recommendations via Monte Carlo simulations for five age groups, neonates,
infants under 6 months, infants 6 months to 2 years, children 2–6 years, and children
6–12 years. For start and target dose simulations the treatment goal was defined to
achieve a 50% probability (start dose) and more than 95% probability (target dose)
to respond to sotalol therapy. An 8-h dosing interval was chosen to ensure a similar
Fig. 5 Simulation results for sotalol dosing recommendation development: (a) Simulated sotalol
trough concentrations (125 patients per group and dose level) for pediatric patients with supraven-
tricular tachycardia. Lines indicate 50% and more than 95% efficacy. (b) Patient fraction with 50%
and more than 95% probability of arrhythmia suppression. Black box plots and hatched bars
indicate recommended dosing range. Arrows indicate start and target doses. From Laer et al.
(2005)
degree of fluctuation between peak and trough sotalol concentrations in children

compared to adults. Dosing recommendations derived from these simulations
for different age groups were a starting dose and target dose of 2 and 4 mg/kg/
day for neonates, 3 and 6 mg/kg/day for infants and children <6 years, and 2 and
4 mg/kg/day for children >6 years (Fig. 5). Since the higher sensitivity of QT
interval prolongation and the higher sotalol exposure in the neonatal age group
increase the risk of potential life-threatening rhythm disturbances, however, sotalol
should in general not be used in neonates due to these safety concerns (Laer et al.
2005).
3.2 Examples of “Bottom Up” Simulations for Deriving Dosing

Recommendations
3.2.1 Physiology-Based Simulations in Individuals with Diseases

and/or Altered Physiology
Physiological changes associated with certain pathological conditions such as liver

cirrhosis or renal insufficiency affect drug pharmacokinetic behavior. PBPK
modeling emerges as an ideal technique to predict drug pharmacokinetics in
patients with altered physiology. One successful example is the study published
by Edginton and Willmann (2008). The objective of the study was to extend an
existing whole-body PBPK model in order to predict drug pharmacokinetics in liver
cirrhosis, so that the model was altered to incorporate physiological differences
between healthy individuals and patients (e.g., changes in blood flows, reduction in
plasma protein synthesis thus an increase in the drug fraction unbound, reduced
hepatic function, etc.). In order to do so, the literature was searched for quantitative
measures of the physiological changes associated with liver cirrhosis and then these
data were incorporated in the modified model. The parameters that were included
were the organ blood flows, cardiac index, plasma-binding proteins, hematocrit,
functional liver volume, hepatic enzymatic activity, and glomerular filtration rate.
Finally, the pharmacokinetic profiles and parameters for four compounds, namely,
alfentanil, lidocaine, theophylline, and levetiracetam were predicted and then
compared with literature data. The simulation results were found to be adequate
when compared with observed data and the model could serve as a building block
for creating a generic/global whole-body PBPK model for the progressive disease
of liver cirrhosis. Figure 6 illustrates predicted and observed arithmetic mean
plasma concentration time curves of alfentanil from patients with liver cirrhosis
according to the classification of Child-Pugh compared to healthy controls.
PBPK models were also successfully applied to describe compound pharmaco-
kinetics during pregnancy both in rat and human. Andrew et al. (2008) built a PBPK
model for the disposition of midazolam in pregnant women.
Fig. 6 Predicted and observed arithmetic mean (SD) plasma concentration time curves of
alfentanil in healthy controls and patients with liver cirrhoses according to Edginton and Willmann
(2008)
3.2.2 Physiology-Based Pharmacokinetic Simulations for Deriving Dosing

Regimens: Prediction of Drug Pharmacokinetics in Different Pediatric
Age Groups
Bj€orkman (2004) presented an example for the prediction of drug pharmacokinetics

in different pediatric age groups. The aim of the study was to create a general PBPK
model for drug disposition in infants and children (neonates, 6 months, 1, 2, 3, 10,
and 15 years old) and to evaluate it with two model drugs with different phy-
sicochemical and pharmacokinetic characteristics, namely, theophylline and
midazolam administered as intravenous application. The model was created using
MATLAB software, including about 13 organs/tissues in addition to the arterial and
venous blood. Data about the various physiological and drug-dependent parameters
for children were incorporated in the model and were obtained either from litera-
ture, scaled from rat to human or calculated from adult values using body surface
area or an age factor. Age-related changes in clearance pathways were also included
and the accuracy and precision of the predictions were assessed via comparison
with the corresponding parameter values obtained from the literature. The results of
the simulation were considered to be adequate. Figure 7 illustrates the predicted
pharmacokinetic parameters for theophylline volume of distribution, clearance, and
terminal half life as function of age, together with literature data.
Fig. 7 Predicted pharmacokinetic parameters for volume of distribution, clearance, and terminal
half-life of theophylline as function of age, together with literature data according to Bj€
orkman (2004)
Another example was presented in Edginton et al. (2006). The goal of this study
was to extend an existing adult PBPK model in order to reflect the age-related
physiological changes in children from birth to 18 years old. Information about age
dependencies of the relevant physiological parameters in children were gathered
from the literature and the simulations were carried out using PK-Sim® in conjuga-
tion with a previously developed age-specific clearance model. To evaluate the
accuracy of plasma profiles prediction in children by the developed pediatric
model, a group of five drugs (paracetamol, alfentanil, morphine, theophylline,
and levofloxacin) was used. These drugs were selected based on the availability
of concentration-time data in the literature for both adults and children. At the
beginning, the pharmacokinetic profile of these drugs was simulated in adults and
was then compared with observed data for evaluation. When the simulated curves
in adults matched the observed data with sufficient accuracy, a predicted pediatric
clearance value for each drug was generated using the clearance model mentioned
previously and pediatric simulations were done. The simulated plasma concentra-
tions–time curves and pharmacokinetic parameters were then compared with the
corresponding observed values and the pediatric simulations were evaluated for
appropriateness. The overlap between predicted and observed data was satisfying.
As already illustrated in Fig. 4, predicted clearance values can be used to calculate
drug exposure and dosing regimens, for example, in specific age groups of children.
4 Improving Clinical Trial Design by Simulations
4.1 Fastening Timelines of Clinical Trials
Unfortunately, many pediatric efficacy trials are still performed with devastating
limitations and design flaws, resulting in a high frequency of trial failures. Benjamin
and co-workers (2008) analyzed these failures in a recent publication on antihyper-
tensive trials. The authors examined six antihypertensive dose-ranging trials with
enalapril, liniopril, losartan, amlodipine, fosinopril, and irbesartan. They could
show that trial failures were largely related to poor dose selection, with widely
overlapping responses for different dose levels. In contrast, successful studies used
wider dose ranges resulting in less overlap in responses. In addition, these studies
used diastolic blood pressure rather than systolic blood pressure, which is more
reflective of systolic hypertension which is more common in elderly, but not in
pediatric populations.
Modeling and simulation approaches, including clinical trial simulation, can
contribute to overcome some of these trial limitations by allowing to explore in
silico different dose levels, dosing regimens, and efficacy biomarkers if the respec-
tive drug- as well as system-specific parameters are available. For antihypertensive
drugs, some of these system-specific parameters may be derived from already
published trials in this indication and population, for example, the typical variability
in systolic and diastolic blood pressure assessment in pediatric populations.
The pharmacometrics team at the US Food and Drug administration recently
published a related example where prior knowledge from an investigational antihy-
pertensive drug together with pediatric data from a drug with similar mechanism of
action and approved indication in pediatric patients were used to perform clinical
trial simulations to explore the optimal choice of dose range, sample size endpoints,
and other design elements (Jadhav et al. 2009).
In another example, Mouksassi et al. (2009) applied clinical trial simulation to
develop a clinical trial design for a pediatric multiple-dose phase I study to
determine the safety, efficacy, and pharmacokinetics of teduglutide, a glucagon-
like peptide-2 analogue indicated for the treatment of short-bowel syndrome and
Crohn’s disease. In this analysis, specific emphasis was put on a realistic simulation
of demographic covariates to obtain an accurate assessment of the variability in the
expected response. This was accomplished with a generalized additive modeling
for location, scale and shape, and qualified with an external age-weight data set.
The analysis allowed to optimize the phase I dosing strategy and the likelihood of
achieving target exposure and therapeutic effect.
4.2 Optimizing Sample Size and Selection of Pharmacokinetic

Sampling Time Points for Pediatric Trials
Willmann (2009) reported an example of using a physiologically based pharmaco-

kinetic model for the determination of optimal sampling times in children. Physio-
logically based pharmacokinetic simulations show special value when the question
arises when to sample plasma in children treated with a drug for the first time. In
this situation, the pediatric pharmacokinetic simulations predict the plasma concen-
tration time curve according to the developmental pharmacology of the specific
drug. The expected plasma concentration range can be balanced with the limit of
quantification (LOQ) of the analytical drug assay. In this way, it might avoid
unnecessary sampling at time points where plasma concentrations are out of the
assay range. A conceptual example is demonstrated in Fig. 8. If we were willing to
conduct a pediatric clinical trial and assuming in which only three blood samples
were allowed to be withdrawn from each child, the sampling times were first chosen
based on the implied adult concentration-time profile (dark arrows). The three time
points were chosen in respect to the limit of quantification of the analytical assay in
a way that the first sample was around the peak concentration, and the remaining
two in the elimination phase in order to make a conclusion about elimination
kinetics. Subsequently, a plasma concentration vs. time profile for a virtual
4-year-old child was simulated with PBPK modeling software PK-SIM®. The
simulation showed an accelerated elimination of the same administered weight-
normalized dose and thus a different time course of the plasma concentration-time
profile. If the same sampling times, determined previously based on adult data,
were applied here for this child, the last sample would be below the detection range,
i.e., drug concentration could not be quantified, the pharmacokinetic analysis would
be impossible, and the child would be exposed to unnecessary strain. However, the
simulation allowed to determine optimized sampling times for children of this age
group.
5 Conclusion
Modeling and simulation techniques used either as “top down” or “bottom up”
approaches are deeply interwoven with pediatric drug development. Within the
three pillars mentioned earlier (see Fig. 1), the modeling and simulation pillar is a
tool that fastens knowledge gaining and helps to understand the pharmacological
properties of the drug in the pediatric population. The idea that modeling and
Plasma
concentration
(log)
Recommended
sampling times
LOQ
3-Year-old chilld Adult Newborn
Time
Fig. 8 Schematic drawing of a potential application of physiology-based pharmacokinetic

simulations for children of different ages to find optimal blood sampling time points for the
pharmacokinetic investigations in a future pediatric trial according to Willmann (2009). Arrows
indicate optimal sampling time for a 3-year-old child, a newborn, and an adult. LOQ Limit of
quantification
simulation alone might be sufficient to solve a pharmacotherapeutic problem

without relying on the proof of the clinical experiment is highly attractive as it
would save substantial costs in the drug development process. Given the complex-
ity, however, of the interaction between human beings and chemical entities, the
complete substitution of clinical trials by simulations if there is no severe constraint
to perform the clinical trial is not a near future scenario. Nevertheless, it is realistic
to assume that simulations can avoid suboptimal trials and can help to reduce the
number of pediatric patients to be included if a qualified model is used to simulate a
range of different dosing regimens and help to decide which doses are most likely to
reach a therapeutic target range.
Unfortunately, up to now software to perform modeling and simulation for the
untrained pediatrician is not available. Therefore, the full value of modeling and
simulation stick to those who are willing to train themselves. For the future, easier
to use software of modeling and simulation for the pediatrician is highly warranted
and would be an excellent tool to achieve a deeper and closer involvement of
pediatric clinical pharmacology and consequently to better treat the pediatric
patient.
Acknowledgement The authors want to thank Feras Khalil from the Department of Clinical
Pharmacy and Pharmacotherapy at the Heinrich-Heine University of D€
usseldorf for some literature
review and comments about the physiologically based pharmacokinetics (see also Khalil and
Laer 2011).
References
Alcorn J, McNamara PJ (2003) Pharmacokinetics in the newborn. Adv Drug Deliv Rev
55:667–686
Andrew MA, Hebert MF, Vicini P (2008) Physiologically based pharmacokinetic model of
midazolam disposition during pregnancy. Conf Proc IEEE Eng Med Biol Soc 54:54–57
Arant BS Jr (1978) Developmental patterns of renal functional maturation compared in the human
neonate. J Pediatr 92:705–712
Bartelink IH, Rademaker CM, Schobben AF et al (2006) Guidelines on paediatric dosing on the
basis of developmental physiology and pharmacokinetic considerations. Clin Pharmacokinet
45:1077–1097
Benjamin DK Jr, Smith PB, Jadhav P et al (2008) Pediatric antihypertensive trial failures: analysis
of end points and dose range. Hypertension 51:834–840
Bj€orkman S (2004) Prediction of drug disposition in infants and children by means of physiologi-
cally based pharmacokinetic (PBPK) modelling: theophylline and midazolam as model drugs.
Br J Clin Pharmacol 59:691–704
Bonate PL (2000) Clinical trial simulation in drug development. Pharm Res 17:252–256
Bouwmeester NJ, Anderson BJ, Tibboel D et al (2004) Developmental pharmacokinetics of
morphine and its metabolites in neonates, infants and young children. Br J Anaesth 92:208–217
Eddy DM, Schlessinger L (2003) Validation of the Archimedes diabetes model. Diabetes Care
26:3102–3110
Edginton A, Willmann S (2008) Physiology-based simulations of a pathological condition:
prediction of pharmacokinetics in patients with liver cirrhosis. Clin Pharmacokinet
47:743–752
Edginton A, Schmitt W, Willmann S (2006) Development and evaluation of a generic physiologi-
cally based pharmacokinetic model for children. Clin Pharmacokinet 45:1013–1034
El-Tahtawy A, Kokki H, Reidenberg BE (2006) Population pharmacokinetics of oxycodone in
children 6 months to 7 years old. J Clin Pharmacol 46:433–442
Girard P (2005) Clinical trial simulation: a tool for understanding study failures and preventing
them. Basic Clin Pharmacol Toxicol 96:228–234
Gobburu JV (2010) How to double success rate of pediatric trials? U.S. Food and Drug Adminis-
tration, Office of Clinical Pharmacology, Silver Spring, MD, http://www.slideshare.net/
JogaGobburu/how-to-double-success-rate-of-pediatric-trials. Accessed 17 Jun 2010
Hines RN (2008) The ontogeny of drug metabolism enzymes and implications for adverse drug
events. Pharmacol Ther 118:250–267
Hsien L (2010) Identifying paediatric needs in cardiology and the prediction of sildenafil exposure
in children with pulmonary arterial hypertension. PhD thesis at the Faculty of Mathematics and
Sciences, University of D€ usseldorf, Germany
Jadhav PR, Zhang J, Gobburu JV (2009) Leveraging prior quantitative knowledge in guiding
pediatric drug development: a case study. Pharm Stat 8:216–224
Johnson TN, Rostami-Hodjegan A, Tucker GT (2006) Prediction of the clearance of eleven drugs
and associated variability in neonates, infants and children. Clin Pharmacokinet 45:931–956
Khalil F, Laer S (2011) Physiologically based pharmacokinetic modeling: Methodology,
applications, and limitations with a focus on its role in pediatric drug development. J Biomed
Biotechnol. In press
Laer S, Wauer I, Behn F et al (2001) Pharmacokinetics of sotalol in different age groups of

children with tachycardia. J Pediatr Pharmacol Ther 6:50–59
Laer S, Elshoff JP, Meibohm B et al (2005) Development of a safe and effective pediatric dosing
regimen for sotalol based on population pharmacokinetics and pharmacodynamics in children
with supraventricular tachycardia. J Am Coll Cardiol 46:1322–1330
Laer S, Barrett JS, Meibohm B (2009) The in silico child: using simulation to guide pediatric drug
development and manage pediatric pharmacotherapy. J Clin Pharmacol 49:889–904
Li F, Nandy P, Chien S et al (2010) Pharmacometrics-based dose selection of levofloxacin as a
treatment for postexposure inhalational anthrax in children. Antimicrob Agents Chemother
54:375–379
Meibohm B, Laer S, Panetta JC et al (2005) Population pharmacokinetic studies in pediatrics:
issues in design and analysis. AAPS J 7:E475–E487
Morselli PL, Morselli-Franco R, Bossi L (1980) Clinical pharmacokinetics in newborns and
infants. Clin Pharmacokinet 5:485–527
Mouksassi MS, Marier JF, Cyran J et al (2009) Clinical trial simulations in pediatric patients using
realistic covariates: application to teduglutide, a glucagon-like peptide-2 analog in neonates
and infants with short-bowel syndrome. Clin Pharmacol Ther 86:667–671
Schlessinger L, Eddy DM (2002) Archimedes: a new model for simulating health care systems – the
mathematical formulation. J Biomed Inform 35:37–50
Sheiner LB, Ludden TM (1992) Population pharmacokinetics/dynamics. Ann Rev Pharmacol
Toxicol 32:185–209
van der Marel CD, Anderson BJ, van Lingen RA et al (2003) Paracetamol and metabolite
pharmacokinetics in infants. Eur J Clin Pharmacol 59:243–251
Willlmann S (2009) The in silico child. Can computer simulations replace clinical pharmacoki-
netic studies? Pharm Unserer Zeit 38:62–67
Willmann S, Lippert J, Sevestre M et al (2003) PK-Sim®: a physiologically based pharmacokinetic
“whole-body” model. Biosilico 1:121–124
Yared A, Ichikara I (1994) Glomerular circulation and function in paediatric nephrology. Williams
and Wilkins, Baltimore
Efficacy Assessment in Paediatric Studies
Siri Wang and Pirjo Laitinen-Parkkonen
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
2 Setting the Scene for Evaluation of Endpoints . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 150
3 Aspects on Determining Endpoints in Paediatric Clinical Trials . . . . . . . . . . . . . . . . . . . . . . . . . 153
3.1 Endpoints Affected by Development and Performance Capacity . . . . . . . . . . . . . . . . . . 154
3.2 Endpoints Influenced by Differences in the Condition . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 157
3.3 Endpoints Depending on Different Symptoms in Adult
and Paediatric Population . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 159
4 Relationship Between Efficacy Measures and Diagnostic Tools . . . . . . . . . . . . . . . . . . . . . . . . . 161
5 Standardisation of Outcome Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
6 Conclusions and Future Developments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 162
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163
Abstract Even though the regulatory authorities to some extent accept the extra-
polation of efficacy data from adults to paediatric patients, it is often the case that
differences in the disease process and the developmental stage of the children
prevent the extrapolation of efficacy in these populations. Where efficacy studies
are needed, the development, validation, and employment of different endpoints for
specific age and developmental subgroups become necessary. Children are in
continuous development and any measure to assess the efficacy of an intervention
should take carefully into account how this development affects the endpoints,
including the performance capacity of the child and differences in the condition and
symptoms presented. Clinical endpoints that are used in the adult trials to evaluate
S. Wang (*)
Norwegian Medicines Agency, Tønsberg Hospital Pharmacy, Sven Oftedalsvei 6, N-0950 Oslo,
Norway
e-mail: siri.wang@noma.no
P. Laitinen-Parkkonen
Health Care and Social Services, City of Hyvink€a€a, Suutarinkatu 2 C, 05801 Hyvink€a€a, Finland
e-mail: pirjo.laitinen-parkkonen@hyvinkaa.fi

150 S. Wang and P. Laitinen-Parkkonen
treatment effect may not be suitable in paediatric studies. The development of

surrogate endpoints for benefit and risk assessment in children is necessary. Col-
laboration between the academic researchers, pharmaceutical industry, and regu-
latory authorities is needed to meet the challenges in proper validation of
biomarkers and surrogate endpoints in paediatric trials.
Keywords Efficacy • Assessment • Paediatric studies • Clinical endpoints •

Biomarkers • Surrogate endpoints • Validation • Standardisation • Outcome
measures
1 Introduction
The regulatory authorities accept to some extent the extrapolation of efficacy data
from adult data to paediatric patients in the case the disease process and the
expected outcome of the therapy are comparable to that of the adults (ICH E 11
2001). However, it is often the case that differences in the disease process and the
developmental stage of the children prevent the extrapolation of efficacy in these
populations. Especially, extrapolation of the efficacy data from older children and
adults to neonate population is rare. Where efficacy studies are needed, it may be
necessary to develop, validate, and employ different endpoints for specific age and
developmental subgroups.
The progress in the legislation regarding the development of medicinal products
based on adequate and well-controlled studies also in paediatric population in the
USA and in EU, such as the Best Pharmaceuticals for Children Act in 2002,
Paediatric Research Equity Act in 2003, and Paediatric Regulation in 2006, has
encouraged the stakeholders to find alternative ways to measure the magnitude of
the treatment response in paediatric population (Regulation EC 2006). Therefore,
the interest on assessing development-appropriate endpoints and developing
biomarkers and surrogate endpoints suitable to paediatric studies has increased.
2 Setting the Scene for Evaluation of Endpoints
The increasing interest on biomarkers has led the working group of National
Institute of Health to provide discussion and definitions for clinical endpoints,
biomarkers, and surrogate endpoints.
A clinical endpoint is defined as a variable reflecting how the patient feels,
functions, or survives. Biomarkers are defined as biological characteristics that can
be objectively measured and evaluated as an indicator of normal biological process,
pathogenic process, or pharmacological response to a therapeutic evaluation
(Biomarkers Definitions Working Group 2001). Biomarkers can be further classi-
fied into Type 0 biomarkers, which are markers of the natural history of a disease
Efficacy Assessment in Paediatric Studies 151
that correlates longitudinally with known clinical indices, and Type I biomarkers,
which capture the effects of a therapeutic intervention in accordance with its
mechanism of action (Puntman 2009). A surrogate endpoint, defined as a biomarker
intended to substitute a clinical endpoint, is not directly measuring clinical impact,
but is believed to adequately reflect the clinical benefit or harm based on epidemio-
logic, pathophysiologic, other scientific evidence, or on therapeutic effect
(Biomarkers Definitions Working Group 2001).
The most robust way to define the clinical impact of the therapeutic intervention
is to use well-defined clinical endpoints in the randomised controlled trials. The
clinical endpoints selected for the trial should provide the clinically relevant and
scientifically sound evidence to support the primary objectives of the study (FDA
1998). The clinical endpoints can be further categorised into intermediate
endpoints, which is not the ultimate outcome, but of clinical benefit such as exercise
tolerance, and into ultimate outcome, such as survival or symptomatic response that
captures the benefits and risks of an intervention (Lesko and Atkinson 2001).
Clinical endpoints that are conventionally used in the adult trials to evaluate
treatment effect may not be suitable in paediatric trials. The experience
accumulated from earlier adult studies for a certain indication may not be applica-
ble in the paediatric population (Della Pasqua et al. 2007). Additionally, in a recent
systematic review, very few paediatric studies even address the choice of outcomes
for clinical research in children (Sinha et al. 2008).
Outcome variables should ideally be measured without bias in a reliable manner
using validated instruments with adequate sensitivity to detect real change in
patient’s health status. The validation process generally assesses this link between
changes in the instrument’s score and the actual clinical benefit and should be
sensitive to treatment effects as well as be clinically relevant (Redmond and Colton
2001). The instrument’s validity might be tested through larger clinical trials, or
through meta-analysis. For children, the challenge will be the feasibility of large
clinical trials and the lack of standardised clinical trial methodology in many
paediatric areas, leaving the validation process potentially even more challenging
than for adults.
Biomarkers and surrogate endpoints frequently used are physiological and
laboratory measurements. The classical examples are the effect of lipid-lowering
drugs on LDL-cholesterol levels as surrogate of the cardiovascular health and the
effect of antihypertensive drugs on blood pressure as surrogate of the stroke.
Biomarkers such as these have traditionally been identified through pathophysio-
logical and epidemiological studies, and some confirmed with clinical trails.
Despite the current acceptance of cholesterol lowering as a surrogate endpoint,
not all treatment effects can be captured by a single biomarker (Lesko and Atkinson
2001). New developments in molecular science and sophisticated imaging
technologies have increasingly facilitated the industrialised process of biomarker
discovery, supported by standardised paradigms of biomarker validation (Puntman
2009; Dancey et al. 2010; EMEA 2009a). There is an ongoing discussion between
the European regulatory authorities, academia and pharmaceutical industry, on the
development and validation of new biomarkers and surrogate endpoints (EMEA

2006a).
The use of surrogate endpoints may facilitate the clinical trials in several ways.
For example, a surrogate endpoint may be more sensitive for detection than the
“golden standard” endpoint enabling the early intervention. The time required to
perform the trial and cost may be reduced (Fleming 2005). A new therapeutical
innovation may also be approved earlier by the regulatory authorities due to the
reduced duration of the trial (ICH E8 1997; FDA 2003, 2009a; Molenberghs and
Orman 2009). These advantages would be welcomed also in the paediatric research.
Accelerated approval and conditional approval processes have been implemented
by the US and European authorities to provide earlier access to new interventions
for diseases with major public health interest when there is an unmet medical need
(FDA 2009b; Regulation EC 2004).
In evaluation of biomarkers, the clinical relevance based on mechanistic or
biochemical connection in the causal chain leading to the clinical endpoint should
be established. Sensitivity and specificity of the treatment effects, defined as the
ability to detect the measurement or change, and assay quality and variability for
quantitating the biomarker need to be explored. However, it should be noted that the
diseases often have multiple causal pathways, and the intervention may lead to
intended as well as unintended actions. Additionally, the measurement should be as
non-invasive and simple as possible (Lesko and Atkinson 2001). The use of
biomarkers as surrogate endpoints further requires the specification of the clinical
endpoints that are being substituted, class of therapeutic intervention being applied,
and characteristics of the population and disease state in which the substitution is
being made (Biomarkers Definitions Working group 2001). The marker must be
correlated with the clinical endpoint, but also fully capture the net effect of the
intervention on the clinical efficacy endpoint. Validation of surrogate endpoint
requires often analysis of many randomised controlled trials to determine the
consistency of effects of the intervention across the drug classes and different
stages of the disease (Fleming 2005; Lesko and Atkinson 2001). This might be
challenging in paediatric population.
The past use of surrogate endpoints in some adult trials has underlined the need
for robust evidence on the association of the surrogate endpoint and the effect. The
results of the CAST study (Cardiac Arrhythmia Suppression Trial) showed that
suppression of ventricular arrhythmias cannot substitute for survival in the evalua-
tion of antiarrhythmic drugs (Echt et al. 1991). The nitric oxide synthase inhibitor,
NG-methyl-L-arginine, promoted the resolution of shock, but was associated with
increased mortality in adults with septic shock (Bakker et al. 2004; Watson et al.
2004; López et al. 2004). On the other hand, in the trial studying interferon gamma
in prevention of infection in chronic granulomatous disease, the surrogate endpoint
did not reveal a therapeutic effect, but showed clinical benefit on reduction of
serious infections (The ICGDC Study Group 1991). These examples emphasise that
a biomarker may reflect only one aspect of the disease process and not the entire
complexity of the disease.
The determination of the clinical benefit related to the surrogate endpoint is

challenging in the children. The development and validation of biomarkers and
surrogate endpoints even in the adult population is still evolving and the reliability
of the surrogates in prediction for long-term benefit and risk in children undergoing
interventions early in life is not known. However, there is a need to develop sound
surrogate endpoints for benefit and risk assessment in paediatric population, which
could be collected using as much non-invasive methods as possible.
3 Aspects on Determining Endpoints in Paediatric

Clinical Trials
Children are in continuous development and any measure to assess the efficacy of
an intervention should take carefully into account how this development affects the
endpoints. For example, in patients with chronic diseases, the response to a medici-
nal product may vary among patients not only because of the duration of the disease
and its chronic effects but also because of the developmental stage of the patient.
Measurement of subjective symptoms such as pain requires different assessment
instruments for patients of different ages, as children may not be able to comply
with the endpoints used in adult trials (ICH 2001).
In neonates, either preterm or full term, symptoms, diseases, and management
might differ significantly from that seen in older children. Thus, when evaluating
medicinal products in neonates, the endpoints should be carefully chosen, linked to
the condition and the degree of prematurity. There is a need for establishing
appropriate surrogate endpoints in this age group. The known complications and
sequelae of prematurity (e.g. intracerebral/intraventricular haemorrhage,
necrotising enterocolitis, retinopathy of prematurity, and bronchopulmonary dys-
plasia) as well as survival should be evaluated at least as secondary endpoints in
trials that include the neonatal population (EMEA 2008a).
When patient reporting-based endpoints are used for defining the magnitude of
treatment benefits, pre-defined age-appropriate instruments are needed (EMEA
2004; Rothman and Kleinman 2009). The current guidance provided by the FDA
on the use of patient reporting-based instruments in children highlights the impor-
tance of age-related vocabulary, language comprehension, comprehension of the
health concept measured, and duration of recall when developing and using such
tools. Instrument development within fairly narrow age groupings is important to
account for developmental differences and to determine the lower age limit at
which children can understand the questions and provide reliable and valid
responses that can be compared across age categories. The proxy-reported outcome
measures for this population are not recommended. For patients who cannot
respond for themselves (e.g. infants), observer reports that include only those
events or behaviours that can be observed are encouraged (FDA 2009c).
This section illustrates some paediatric-specific issues on assessing efficacy in
clinical studies. Examples given are not intended to cover all aspects or areas, nor
intended as complete scientific or regulatory guidance, but aim to reflect some of

the challenges in assessing efficacy in paediatric trials. Many endpoints might be
simultaneously influenced by developmental stage, disease variants, and
differences in symptoms and performance capacity in the relevant population.
The referred paediatric guidelines and addendums provided by the EMA may not
necessarily be fully reported.
3.1 Endpoints Affected by Development and Performance

Capacity
Treatment of obesity could serve as a simple but nevertheless illustrative example

on how growth might have a direct effect on the efficacy endpoint. The adult
standard goal being weight reduction would not necessarily be as relevant in a
paediatric obesity study. Thus, halting abnormal or excess weight gain or decreas-
ing the rate of weight gain could be important goals in a growing child and as well
serve as endpoints (EMEA 2008b), whereas they would not be considered appro-
priate endpoints in adults.
Sometimes the standard methods to measure the degree of symptoms might
differ significantly between adults and children, regardless of whether the disease
and the symptoms per se might be considered the same as in older subjects. This is
particularly relevant when “performance tests” are used as efficacy measures.
Measuring lung function is one of the obvious endpoints in asthma studies. How-
ever, the use of spirometry and other measures recommended for older children and
adult such as airway responsiveness and markers of inflammation might be difficult
in infants and pre-school children, as it requires complex equipment and/or coordi-
nation and cooperation beyond that can be given by children in this age group for
appropriate reproducibility and accuracy. The actual lower age group in which
adequate tests can be performed is being discussed and might depend significantly
on training of the individual child (Crenesse et al. 2001). Spirometry could be
considered feasible in children over 3 years, but its usefulness is the lower age
group will depend on thorough training. Although so far limited used in clinical
trials, either FEV0,5 or FEV0,75 might be a better measure than FEV1 (CPMP, 2009;
Beydon et al. 2007). Specific airway resistance (sRaw) measured by
plethysmography or other validated methods, combined with clinical symptom
scores, can be used in children aged 2–6 years (CPMP, 2009). The aspects of
appropriate endpoints add to other challenges in many paediatric asthma studies:
the difficulties in precisely diagnosing asthma in the youngest cohorts, uncertainties
regarding severity classifications, and the practical aspects of age-appropriate
formulations and devices. As the need for and possibilities of early and more
precise asthma diagnosis and treatment evolve, the search for appropriate endpoints
in infants and pre-school children is considered of great importance.
Even more evident is this need for appropriate lung function tests in cystic
fibrosis, where diagnosis can easily be done at an early stage and treatment effect
could be significant in the first years. Currently, the primary goal of cystic fibrosis
therapy is supportive and includes slowing the decline in lung function by clearing
airways of mucus and controlling respiratory infections and inflammation to
improve or maintain respiratory function. As in asthma, FEV1 is the recommended
primary endpoint, but similarly sub-optimal or potentially inappropriate in children
beyond 5–6 years. As stated in the recently updated EMA guideline (EMEA
2009b), respiratory function tests in young children can be performed in specialised
centres able to promote standardised methods. Tests currently used include
plethysmography and RVRTC (compression technique) (Davis et al. 2010;
Rosenfeld 2007), but these procedures most often require sedation, partly
depending on age group (Davis et al. 2007). Measuring lung clearance index
(LCI) by multiple breath washouts might show to be a useful method for appropri-
ate lung function testing in younger children. However, these alternative measures
still need to be further validated.
Although paediatric pulmonary arterial hypertension (PAH) differs in physiology,
progression rate, and treatment response compared to the adult type, the definition
of PAH is basically the same (EMA 2010) and the symptoms are similar although
with potential different severity (Haworth and Beghetti 2010). However, the tradi-
tional endpoint used in adult studies of pulmonary hypertension, the 6-min walking
test (6MWT), is of questionable value in younger children (<6 years), obviously
inappropriate in the very youngest infants, but considered valid at least in
adolescents. In the age group 7–11 years, this test needs further validation (Li
et al. 2005). Additionally, its predictive value on the long-term improvement of the
disease is not established in the adult population, questioning its usefulness in the
paediatric population >6 years (EMEA 2009c).
Time to clinical worsening (TTCW) is probably a more appropriate endpoint to
assess disease progression, and is also used in adults. Of note, the definition of the
composite endpoint of clinical worsening in children will have to be done carefully.
In particular, there is a need for paediatric-specific endpoints that could be used in
intervention studies in the early phase of the disease to prevent the fast deterioration
seen in many children. TTCW could be such an endpoint (Haworth and Beghetti
2010).
Data on vascular resistance, obtained by invasive haemodynamic measurements
or by non-invasive techniques such as echocardiography, could potentially serve as
a surrogate endpoint and should be studied as additional endpoint to assess the
correlation to final clinical outcome in paediatric studies.
Even more limited data are available regarding relevant endpoints in the field of
persistent pulmonary hypertension of the neonate (PPHN), having different
aetiology and management and being considered a different clinical entity. At
present, several potential endpoints might be useful; however, all-cause mortality
and the need for membrane oxygenation (ECMO) are considered the less disputable
ones (EMA 2010).
Another example of challenges in assessing efficacy in children is the evaluation
of pain. According to the International Association of study of pain (IASP), pain
includes an unpleasant sensory and emotional experience associated with actual or
potential tissue damage, or described in terms of such damage (Merskey and

Bogduk 1994). In children, there are differences across the paediatric age span in
the causes and the experience of acute pain (Jacobson 2007; Fradet et al. 1990). In
chronic and recurrent pain conditions, such as migraine and tension headache, the
incidence increases with the onset of puberty (see also section “EndPoints
Depending on Different Symptoms in Adult and Pediatric Population”). The inci-
dence and course of neuropathic pain can vary substantially, depending on the
contextual factors (Walco et al. 2010). In addition, the spectrum of cognitive,
emotional, and physical capabilities, all related to the pain experience, is changing
during the childhood (Hain 1997; McGrath et al. 2008).
The pain intensity is the core outcome domain in pain trials. The regulatory
guidelines recommend the use of rating scales in the evaluation of time-specific
pain intensity difference and pain relief endpoints in trials for nociceptive pain in
adult trials whenever it is possible, including responder rates. Other endpoints, such
as patient global assessments, functional performance indicators, and validated
questionnaire scores should also be considered in accordance with the intended
indications and study designs (EMEA 2002). In paediatric acute pain consensus
statement, the pain intensity, global judgement of satisfaction with treatment,
symptoms, and adverse events, physical recovery, emotional response, and eco-
nomical factors are proposed as the core outcome domains in children older than
3 years. In chronic and recurrent pain, physical, role, and emotional functioning and
sleep are suggested to be added as the core outcome domains, depending on the
specific aims of the trial (McGrath et al. 2008).
The main approaches to measure pain in children are the use of self-reports,
observational or behavioural, and physiological measures (Walco et al. 2005).
Despite the recognition of the multidimensional nature of pain, self-reporting of
the pain intensity is commonly used in paediatric clinical pain trials. The develop-
mental factors related to the ability of the child to provide self-assessment are not
fully described (Champion et al. 1998; Stinson et al. 2006; Stanford et al. 2006). For
the moment, there is no single tool to evaluate the pain intensity with self-reports
across the age span and different types of pain. For procedure-related and postop-
erative pain, the use of Poker Chip Tool (pieces of hurt) has been recommended in
children from 3 to 4 years and Visual Analog Scale from 8 years on. The Faces Pain
Scale – Revised has been recommended in children from 4 to 12 years old also in
disease-related chronic pain. In pre-school-aged children, the inclusion of observa-
tional measures as secondary outcome might be needed due to the wide variability
in young children’s ability to use the self-report tools (Stinson et al. 2006). Further
studies on validation of Numerical Rating Scale have suggested its usefulness in
self-reporting in children of 8 years and older (von Baeyer et al. 2009)
The observational measures of pain are needed for children who are too young to
understand and use a self-report scale or too distressed to use it. In addition, the
cognitive and communicative impairment may preclude the use of self-reporting
tools. Mechanical ventilation, sedative drugs, restrictive bandages etc. also affect
the ability of the child to comply with the self-rating measurements (von Baeyer
and Spagrud 2007). From 1 year and above, the FLACC (Face, Legs, Arms, Cry,
Consolability) tool is recommended for procedural and postoperative pains in

hospital (Merkel and Voepel-Lewis 1997; Nilsson et al. 2008). In addition, the
CHEOPS tool (Children’s Hospital of Eastern Ontario Pain Scale) could be used
(von Baeyer and Spagrud 2007). The COMFORT scale is recommended for
children aged 1 year and above undergoing critical care (van Dijk et al. 2000).
Additionally, measures for pain evaluation at home, the Parent’s Postoperative Pain
Measure, are available.
For the moment, more information on observational tools in chronic pain
conditions as well in children with cognitive impairment is warranted.
The validation of other outcome measures proposed for paediatric pain trials is
largely missing. Multidimensional assessment tools such as Paediatric Quality of
Life (PedsQL) may be used (Varni et al. 1999). Recently, new composite measure
of chronic pain, the Bath Adolescent Pain Questionnaire, has been developed, but
further studies are needed on the subscales (Eccleston et al. 2005). For emotional
responses, tools for assessing the perioperative anxiety as a part of the pain
experience have been developed, but further research is needed to establish their
use (Bringuier et al. 2009).
In neonates and infants, many behavioural and physiological assessment tools
are available, but few are fully validated (Grunau et al. 1998; Debillon et al. 2001;
Loizzo 2009). The behaviour of infants having a large number of procedures may
become habituated or sensitised depending on the temporal proximity of repeated
procedures, motor development, and previous handling. Overlap with
manifestations of other states of distress and confounding clinical factors can
further reduce the specificity of behavioural and physiological responses (Walker
2008) The widely used premature infant pain profile (PIPP), for example, measures
behaviours such as sleep state and change in facial expression to produce a age-
weighted composite pain score (Stevens et al. 1996). Such scores have become the
major outcome measure despite the fact that they might reflect the activation of
subcortical somatic and autonomic motor pathways and may not be reliably linked
to central sensory or emotional processing in the brain (Anand et al. 2004).
Biomarkers such as non-invasive near-infrared spectroscopy measurements,
which are reflecting the functional activation of the cortex, have recently been
proposed to be used in evaluation of pain assessment tools with respect to the
sensory input and establish whether the resultant PIPP scores reflect cortical pain
processing (Slater et al. 2008). The development of new markers is needed, but
whether they can be used as endpoints warrants further investigation.
3.2 Endpoints Influenced by Differences in the Condition
As disease course as well as consequences might not necessarily be the same for
different paediatric variants of a condition, the aims of the treatment might vary and
this could also affect the endpoints. For example, for incontinence in children,
while the goal for all children would be continence, in neurogenic detrusor
overactivity (NDO), as compared to overactive bladder (OAB), reducing renal

pressure per se is also a major goal to minimise the risk of renal effects. Thus,
urodynamic measures such as cystometric capacity should be assessed in NDO
studies but will not be meaningful in OAB studies. Again, the ability of the children
to “perform” reflects the appropriate endpoints: while adult incontinence studies
would focus on both urgency and incontinence, younger children would have
difficulties indicating and expressing bladder sensation differences and only incon-
tinence would be a useful endpoint.
The pathophysiology of sepsis is a complex disturbance in the equilibrium
between pro-inflammatory response and concomitant anti-inflammatory mech-
anisms, and the ways to modulate it to improve patient outcomes are not yet fully
understood even in adult population. The mortality rates reported in paediatric
severe sepsis range from about 4 to 20%, and it is even higher in patients with
underlying co-morbidities and organ dysfunction and in children in developing
countries, remaining a major health and resource burden (Watson and Carcillo
2005; Inwald et al. 2009; de Oliveira et al. 2008; Odetola et al. 2007). In paediatric
patients, the developmental changes in preterm and term neonates, infants, and
children and the haemodynamic reserves available complicate the definition of
endpoints in the paediatric sepsis trials. Haemodynamic responses of premature
neonates with septic shock are least understood (Goldstein et al. 2005; Brierley
et al. 2009).
Currently, there is no consensus on basic measures for conducting trials in
paediatric severe sepsis and the outcome definitions. For the time being, the main
variables defined to direct treatment of paediatric septic shock are the clinical,
oxygen utilisation-related, and haemodynamic variables, but there is no agreement
on the use of cellular variables (Carcillo et al. 2002; Brierley et al. 2009). Due to the
reasonably low mortality rate in paediatric sepsis, the use of mortality endpoints
which are widely agreed in the adult population would need a large number of
paediatric subjects to demonstrate differences between the treatment modalities
(EMEA 2006b; Vincent 2004). Many children have underlying diseases different
from adults, and mortality is not reflecting the increasing morbidity after the sepsis
event. The use of endpoints such as organ failure-free days, organ failure resolution
time, ICU-free days, and progression of the disease has been proposed as primary
endpoints. Validated organ failure scores for neonates are lacking for the moment,
even though scores for older children have been developed. The external validation
of many of the scores is lacking. Health consequences and health-related quality of
life should also be considered as endpoints (Goldstein et al. 2005; Buysse et al.
2008; Varni et al. 2001; Curley and Zimmerman 2005).
Assessing degree of disease and treatment effects is particularly challenging in
complex diseases such as JIA (juvenile idiopathic arthritis). Extrapolation from
efficacy results in adult RA is mostly inappropriate since JIA represents a group of
different diseases divided into several categories with different prognoses and
variable clinical presentation also within the paediatric population (CPMP 2007)
In JIA, both assessment of disease severity and quantification of disease activity
over time are important for optimal evaluation of the effectiveness of antirheumatic
drugs. A variety of instruments are available for measuring disease activity; how-
ever, no single measure would be considered optimal for all patients. Therefore,
a core set of parameters has been established by the American College of Rheuma-
tology (ACR) that includes physician scoring, parent assessment, affected joint
counts, functional assessment, and laboratory measures, particularly tailored for the
paediatric condition (ACR Pedi 30, Pedi 50 and Pedi 70). These tools focus on
individual changes in disease activity over time and as such are useful for assessing
the effect of an intervention. However, comparison of absolute disease activity
between individuals and group comparison is not optimal with this scoring system.
Thus, a composite disease activity score for JIA has been developed, called the
Juvenile Arthritis Disease Activity Score (JADAS), enabling a single continuous
measure of disease activity (Consolaro et al. 2009). The score has been developed
and validated by the Paediatric Rheumatology International Trials Organisation
(PRINTO) and could be of significant value both in standard clinical care and
particularly in clinical trials, potentially minimising inter-centre variations and
thereby reducing the sample size required in clinical trials.
The establishment of international networks within the area of paediatric rheu-
matic diseases has significantly contributed to the standardisation of the evaluation
of response to therapy in juvenile idiopathic arthritis (JIA), juvenile systemic lupus
erythematosus (JSLE), and juvenile dermatomyositis (Ruperto et al. 2006).
It should be noted that even if a disease differ between adults and children
this may not necessarily have impact on the choice of endpoint, as for some
conditions the same endpoints might be appropriate, although the disease is not to
be considered entirely the same. In these cases, separate studies could be needed or
at least provide more meaningful data, since the effect of the intervention could
differ for the separate subtypes of the diseases and significantly influence the
outcome of the trials.
3.3 Endpoints Depending on Different Symptoms in Adult

and Paediatric Population
Sometimes symptoms of a condition might be different in children compared to

adults. Thus, these symptoms are relevant as endpoints in adult studies but would
not be considered optimal for children, and therefore specific paediatric symptoms
will have to be considered as potential endpoints in the paediatric study.
Migraine with or without aura in early childhood is rare, but the prevalence rate
is increasing with age up to 5–10%, being even higher and comparable to that of
adults in the onset of adolescence (Mortimer et al. 1992; Abu-Afereh and Russel
1994). Due to different disease characteristics in paediatric population, the extrap-
olation of adult study results in this population is difficult (EMEA 2007b). Addi-
tionally, the disease characteristics may change according to the age and maturation
stage of the patient (Crawfordt et al. 2009). According to the International
Headache Society (IHS) standards, the definition of the attack differs in pre- and
post-pubertal children (IHS 2004).
Several investigators have observed the high and variable placebo response
observed in many migraine trials in paediatric population, which makes it difficult
to assess efficacy (Winner et al. 2007; H€am€al€ainen et al. 1997; Ahonen et al. 2004,
2006; Rothner et al. 2006). The reasons for the high placebo response in children
are not fully understood. The proposed underlying reasons include differences in
presentation of the disease, such as the shorter attacks in children, especially in
adolescents, compared to adults, and the different baseline severity of attacks. The
trial design-related issues (such as cross-over versus parallel group) and site
selection may also affect the placebo response as well as communication and
expectancy of the caregivers (Evers et al. 2008; Rothner et al. 2006). Additionally,
the sensitivity of the pain rating scales to distinguish the differences in the pain
intensity in children should be confirmed (Lewis et al. 2005).
The European regulatory guidelines recommend the percent of patients being
pain-free at 2 h after administration of the study agent as primary endpoints in acute
paediatric migraine treatment trials similarly as in adults. Recommended secondary
endpoints are, for example, the percent of patients pain-free at 2 h after administra-
tion of the study product with no use of rescue medication and no relapse within
48 h after administration of the study agent, percentage of subjects with partial
relief (including children asleep in 2 h), use of rescue medication, global evaluation
by patient and/or parents, and functional disability at 2 h and other time points (e.g.
using behavioural scales). In prophylaxis studies, the frequency of the attacks and
the speed of effect should be monitored (EMEA 2007b).
It has been suggested to explore other primary endpoints as well, such as the
migraine-free primary endpoint (pain-free and symptom-free composite endpoint),
1-h headache response, coupled with the 2-h sustained response and the 24-
h sustained headache, and pain-free response to handle the outcome challenge
(Lewis et al. 2005; Lewis 2007; Winner et al. 2007). New approaches in the
study design are warranted to meet the challenges of efficacy assessment in
developmental age migraine.
Studies on antihypertensive treatment with ACE inhibitors and ARBs for
paediatric hypertension have revealed diverging results. Attempts to analyse the
different factors influencing success or failure of these trials have shown that in
addition to trial design, dose ranges tested, and dosing accuracy, the choice of
primary endpoint might also be relevant (Benjamin et al. 2008). Using change in
diastolic blood pressure (DBP) instead of sitting systolic blood pressure (sSBP) as
the primary endpoint seemed to give a closer relationship between dosage and
blood pressure reduction, probably related to the less variability seen for DBP
measures compared to SBP, underlining the potential importance of the inherent
characteristics of the endpoint of choice. Another aspect would be that these two
endpoints, when used as tools for inclusion, could select different population
subsets and thereby affect outcome of the trials. Which endpoint that best correlate
to hard cardiac endpoints in children is a vital question. Discussion is ongoing
on which endpoint to be considered optimal, also taking into account the
different prevalence of the two hypertension subtypes (EMEA 2008c). It is pro-

posed that using mean arterial pressure as a primary endpoint, incorporating both
SBP and DBP values, might prove advantageous, and this possibility should be
explored in future trials. Perhaps even more beneficial would be the use of ambula-
tory BP monitoring in paediatric clinical trials for antihypertensive medications (Li
et al. 2010).
In acute heart failure in adults, dyspnoe is the most commonly reported symp-
tom and useful scores exists for adult studies. However, dyspnoe is not an equally
significant symptom in children. In addition, the assessment, including communi-
cation, of this symptom might be challenging. In infants, heart failure often presents
with breathing trouble, poor feeding, poor growth, excessive sweating, or even low
blood pressure. No clinical trials in acute heart failure have evaluated dyspnoe as an
endpoint in children. Although scales exist for grading the severity of congestive
heart failure in infants (Ross et al. 1992), their usefulness as a single endpoint in
clinical trials are limited. Obviously, because death is a relatively rare outcome - in
clinical trials – in children with heart failure, alternative endpoints as rate of weight
gain, length of hospital stay, and surgical morbidities might be useful (Madriago
and Silberbach 2010).
Few studies have yet been performed in children with heart failure and no
composite endpoints have been validated for heart failure studies in children. One
study, reporting of carvedilol, failed to show efficacy of medical intervention. A
composite clinical outcome measure was used as primary endpoint, including death,
hospitalisation, need for intravenous medication, worsening of severity and of
global assessment score. However, its appropriateness has been debated. The
authors conclude that “The inherent heterogeneity of paediatric patients with heart
failure and their high rate of spontaneous improvement make the definition of
suitable clinical endpoints with a feasible sample size and sufficient statistical
power a challenge for future trials in this population” (Shaddy et al. 2007). Plasma
brain natriuretic peptide (BNP) levels have been discussed and also used as second-
ary endpoint in paediatric trials; however, as the BNP levels seem quite low in this
population compared to adults, its usefulness might be limited (Shaddy et al. 2007).
As some of these examples show, different disease symptoms would call for
specific paediatric endpoints even if the disease is considered the same from a
pathophysiological point of view. In some of such cases, however, extrapolation of
efficacy from data in adults could be possible, even though the adult endpoints
would not have been appropriate if used in a paediatric study.
4 Relationship Between Efficacy Measures and Diagnostic Tools
As briefly mentioned in the examples of lung function tests in asthma, the possibil-
ity to make an appropriate diagnosis in children is often hampered by the lack of
relevant measures to properly define the condition. Consequently, further research
on diagnosis-related pathophysiological measures and severity classification of
diseases would also be relevant for further measures of drug efficacy, as the same
methods might be valid for both appropriate diagnoses and appropriate endpoints
for measuring any effect of intervention.
The development of biomarkers may also facilitate the understanding of disease
mechanisms and natural history, expedite the development of new diagnostic tools,
and assist the clinical practice (Lesko and Atkinson 2001).
5 Standardisation of Outcome Measures
For many paediatric diseases, performance of meaningful clinical trials is made

difficult because of the small number of eligible patients and heterogeneity of the
patient group. In these cases, the fact that different trial uses different inclusion
criteria and especially a variety of outcome measures makes it hard to optimally
assess the effect of interventions. Obviously, the use of wrong or inappropriate
endpoint in paediatric studies implies waste of resources and potentially misleading
information though the risk of under- or overestimating the effects of an interven-
tion. Also, using non-standardised criteria for either inclusion or assessment of
clinical response would make meta-analysis and comparison of different studies
difficult.
As previously mentioned, very few paediatric studies address the choice of
outcomes for clinical research in children (Sinha et al. 2008). There are initiatives
for development and application of agreed standard sets of outcomes, such as
OMERACT, IMMPACT, PedIMMPACT, and COMET (Tugwell and Boers
1993; Dworkin et al. 2005; McGrath et al. 2008; University of Liverpool 2010).
Such initiatives are of particular relevance in paediatrics where limited numbers of
children are included in the trials, the total number of trials is small, and significant
effort should be made to avoid unnecessary studies.
6 Conclusions and Future Developments
In this chapter, we have discussed the challenges in assessing efficacy in paediatric

trials. In spite of recent developments in legislation and in science, there are still
significant unmet medical needs in the paediatric population. This is most promi-
nent in neonates.
Further research on age- and disease-appropriate endpoints for children is
necessary. The use of surrogate endpoints is particularly intriguing for paediatric
clinical trials, enabling indication of long-term patient outcome by short-term
measures of response, and thereby avoiding unnecessary studies. Inevitably, under-
standing the paediatric variant of a condition and its potential differences compared
to adults is crucial in selecting the appropriate surrogate endpoints for paediatric
trials. The challenges in proper validation of biomarkers and surrogate endpoints
are obvious and significant focus should be put on these aspects to facilitate optimal
clinical trials in children. Collaboration and sharing the advances between acade-
mia, pharmaceutical industry, and regulatory authorities are of paramount
importance.
Disclaimer. The views expressed here are the personal views of the authors and
may not be understood or quoted as being made on behalf of the Paediatric
Committee or reflecting the position of the Paediatric Committee.
References
Abu-Afereh I, Russel G (1994) Prevalence of headache and migraine in school children. BMJ
309:765–769
Ahonen K, H€am€al€ainen ML, Rantala H, Hoppu K (2004) Nasal sumatriptan is effective in
treatment of migraine attacks in children: a randomized trial. Neurology 62:883–887
Ahonen K, H€am€al€ainen ML, Eerola M, Hoppu K (2006) A randomized trial of rizatriptan in
migraine attacks in children. Neurology 67:1135–1140
Anand KJ, Hall RW, Desai N, Shepard B, Bergqvist LL, Young TE, Boyle EM, Carbajal R,
Bhutani VK, Moore MB, Kronsberg SS (2004) NEOPAIN Trial Investigators Group. Effects of
morphine analgesia in ventilated preterm neonates: primary outcomes from the NEOPAIN
randomised trial. Lancet 363:1673–1682
Bakker J, Grover R, McLuckie A, Holzapfel L, Andersson J, Lodato R, Watson D, Grossman S,
Donaldson J, Glaxo Wellcome International Septic Shock Study Group (2004) Administration
of the nitric oxide synthase inhibitor NG-methyl L-arginine hydrochloride (546C88) by
intravenous infusion for up to 72 hours can promote resolution of shock in patients with severe
sepsis: results of a randomized, double-blind, placebo-controlled multicenter study (study no
144-002). Crit Care Med 32:1–12
Benjamin DK Jr, Smith PB, Jadhav P, Gobburu JV, Murphy MD, Hasselblad V, Baker-Smith C,
Califf RM, Li JS (2008) Paediatric antihypertensive trial failures: analysis of endpoints and
dose range. Hypertension 51:834–840
Best Pharmaceuticals for children Act (2002) Public Law No 107–109
Beydon N, on behalf of the American Thoracic Society/European Respiratory Society Working
Group on Infant and Young Children Pulmonary Function Testing et al (2007) An official
American Thoracic Society/European Respiratory Society statement: pulmonary function
testing in preschool children. Am J Respir Crit Care Med 175:1304–1345
Biomarkers Definitions Working Group (2001) Biomarkers and surrogate endpoints: preferred
definitions and conceptual framework. Clin Pharmacol Ther 69:89–95
Brierley J et al (2009) Clinical practice parameters for hemodynamic support of pediatric and
neonatal septic shock: 2007 update from the American College of Critical Care Medicine. Crit
Care Med 37:666–688
Bringuier S, Dadure C, Raux O, Dubois A, Picot M-C, Capdevila X (2009) The perioperative validity
of the visual analog anxiety scale in children: a discriminant and useful instrument in routine
clinical practice to optimize postoperative pain management. Anesth Analg 109:737–744
Buysse CM, Raat H, Hazelzet JA, Hop WC, Maliepaard M, Joosten KFM (2008) Surviving
meningococcal septic shock: health consequences and quality of life in children and their
parents up to 2 years after pediatric intensive care unit discharge. Crit Care Med 36:596–602
Carcillo JA, Fields AI, Task force committee members (2002) Clinical practice parameters for
hemodynamic support of paediatric an neonatal patients in septic shock. Crit Care Med
30:1365–1378
Champion GD, Goodenough B, von Baeyer CL, Thomas W (1998) Measurement of pain by self-
report. In: Finley GA, McGrath PJ (eds) Measurement of pain in infants and children. IASP,
Seattle, WA, pp 123–160
Consolaro A, Ruperto N, Bazso A, Pistorio A, Magni-Manzoni S, Filocamo G, Malattia C, Viola S,

Martini A, Ravelli A, for the Pediatric Rheumatology International Trials Organisation (2009)
Development and validation of a composite disease activity score for juvenile idiopathic
arthritis. Arthritis Rheum 61(5):658–666
CPMP/EWP/4151/00 (2009) Rev. 1. Guideline on the requirements for clinical documentation for
Orally Inhaled Products (OIP) including the requirements for demonstration of therapeutic
equivalence between two inhaled products for use in the treatment of Asthma and Chronic
Obstructive Pulmonary Disease (COPD) in adults and for use in the treatment of Asthma in
children and adolescents
CPMP/EWP/422/04 (2007) Guideline on clinical investigation of medicinal products for the
treatment of juvenile idiopathic arthritis
Crawfordt MJ, Lehman L, Slater S, Kabbouche MA, LeCates SL, Segers A, Manning P, Powers
SW, Hershey AD (2009) Menstrual migraine in adolescents. Headache 49:341–347
Crenesse D, Berlioz M, Bourrier T, Albertini M (2001) Spirometry in children aged 3 to 5 years:
reliability of forced expiratory maneuvers. Pediatr Pulmonol 32:56–61
Curley MA, Zimmerman JL (2005) Alternative outcome measures for pediatric clinical sepsis
trials. Pediatr Crit Care Med 6(Suppl):S150–S156
Dancey JE, Dobbin KK, Groshen S, Milburn Jessup J, Hruszkewycz AH, Koehler M, Parchment
R, Ratain MJ, Shankar LK, Stadler WM, True LD, Gravell A, Grever MR, On behalf of the
Biomarkers Task Force of the NCI Investigational Drug Steering Committee (2010) Guidelines
for the development and incorporation of biomarker studies in early clinical trials of novel
agents. Clin Cancer Res 16:1745–1755
Davis SD, Brody AS, Emond MJ, Brumback LC, Rosenfeld M (2007) Endpoints for clinical trials
in young children with cystic fibrosis. Proc Am Thorac Soc 4:418–430
Davis SD, Rosenfeld M, Kerby GS, Brumback L, Kloster MH, Acton JD, Colin AA, Conrad CK,
Hart MA, Hiatt PW, Mogayzel PJ, Johnson RC, Wilcox SL, Castile RG (2010) Multicenter
evaluation of infant lung function tests as cystic fibrosis clinical trial endpoints. Am J Respir
Crit Care Med 182(11):1387–1397
de Oliveira CF, de Oliveira DSF, Gottschald AFC, Moura JDG, Costa GA, Ventura AC, Fernandes
JC, Vaz FAC, Carcillo JA, Rivers EP, Troster EJ (2008) ACCM/PALS haemodynamic support
guidelines for paediatric septic shock: an outcomes comparison with and without monitoring
central venous oxygen saturation. Intensive Care Med 34:1065–1075
Debillon T, Zupan V, Ravault N, Magny J-F, Dehan M (2001) Development and initial validation
of the EDIN scale, a new tool for assessing prolonged pain in preterm infants. Arch Dis Child
Fetal Neonatal Ed 85:F36–F41
Della Pasqua O, Zimmerhackl L-B, Rose K (2007) Study protocol design for paediatric patients of
different ages. In: Rose K, van den Acker JN (eds) Guide to paediatric clinical research. Basel,
Karger, pp 87–107
Dworkin RH, Turk DC, Farrar JT, Haythornthwaite JA, Jensen MP, Katz NP, Kerns RD, Stucki G,
Allen RR, Bellamy N, Carr DB, Chandler J, Cowan P, Dionne R, Galer BS, Hertz S, Jadad AR,
Kramer LD, Manning DC, Martin S, McGormick GC, Mc Dermott MP, McGrath P, Quessy S,
Rappaport BA, Robbins W, Robinson JP, Rothman M, Royal MA, Simon L, Stauffer JW,
Stein W, Tollet J, Wernicke J, Witter J (2005) Core outcome measures for chronic pain trials:
IMMPACT recommendations. Pain 113:9–19
Eccleston C, Jordan A, McCracken LM, Sleed M, Connell H, Clinch J (2005) The Bath Adolescent
Pain Questionnaire (BAPQ): development and preliminary psychometric evaluation of an
instrument to assess the impact of chronic pain on adolescents. Pain 118:263–270
Echt BS, Liebson PR, Mitchell LB (1991) Mortality and morbidity in patients receiving ecainide,
flecainide or placebo. The cardiac arrhythmia suppression trial. N Engl J Med 324:781–788
EMA/CHMP/EWP/213972/2010 (2010) Paediatric addendum to CHMP guideline on the clinical
investigations of medicinal products for the treatment of pulmonary arterial hypertension
EMEA/522496/2006 (2006a) Report on the EMEA/CHMP biomarkers workshop
EMEA/536810/08 (2008a) Guideline on the Investigation of medicinal products in the term and
preterm neonate
EMEA/CHMP/EWP/139391/2004 (2004) Reflection paper on the regulatory guidance for the use
of health-related quality of life (HRQL) measures in the evaluation of medicinal products
EMEA/CHMP/EWP/4713/03 (2006b) Guideline on clinical investigation of medicinal products
for the treatment of sepsis
EMEA/CHMP/EWP/517497/2007 (2008b) Guideline on clinical evaluation of medicinal products
used in weight control (cpmp/ewp/281/96 rev. 1) Addendum on weight control in children
EMEA/CHMP/EWP/545456/2008 (2008c) Concept paper on the need for the development of a
paediatric addendum to the note for guidance on the clinical investigation on medicinal
products in the treatment of hypertension
EMEA/CHMP/EWP/644261/2008 (2009c) Concept paper on the need for the development of a
paediatric addendum to the CHMP guideline on the clinical investigations of medicinal
products for the treatment of pulmonary arterial hypertension
EMEA/CHMP/EWP/9147/2008 (2009b) Guideline on the clinical development of medicinal
products for the treatment of cystic fibrosis
EMEA/CHMP/ICH/380636/2009 (2009a) Note for guidance on genomic biomarkers related to
drug response: context, structure and format of qualification submissions
EMEA/CPMP/EWP/612/00 (2002) Note for guidance on clinical investigation of medicinal
products for treatment of nociceptive pain
EMEA/CPMP/EWP/788/01 (2007) Rev. 1. Guideline on clinical investigation of medicinal
products for the treatment of migraine
Evers S, Marziniak M, Frese A, Gralow I (2008) Placebo efficacy in childhood and adolescence
migraine: an analysis of double-blind and placebo-controlled studies. Cephalgia 29:436–444
Fleming TR, DeMets DL (1996) Surrogate endpoints in clinical trials: are we being misled? Ann
Intern Med 125:605–613
Food and Drug Administration (1998) US Departmentof Health and Human Services. Guidance
for industry; E9 statistical principles for clinical trials. Office of Training and Communications,
Rockville, MD
Food and Drug Administration (2003) Code of Federal Regulations 601.40
Food and Drug Administration (2009a) Code of Federal Regulations 21 314.50
Food and Drug Administration (2009b) Accelerated approval of new drugs for serious or life-
threatening illnesses. Code of Federal Regulations, Title 21, Volume 5, revised
Food and Drug Administration (2009c) Guidance for industry. Patient-reported outcome
measures: use in medicinal product development to support labeling claims
Fradet C, McGarth PJ, Kay J, Adams S (1990) A prospective survey of reactions to blood test by
children and adolescents. Pain 40:53–60
Goldstein B, Giror B, Randolph A, and the Members of the International Consensus Conference of
Pediatric Sepsis (2005) International pediatric sepsis consensus conference: Definitions for
sepsis and organ dysfunction in pediatrics. Pediatr Crit Care Med 6:2–8
Grunau RE, Oberlander T, Holsti L, Whitfield MF (1998) Bedside application of the Neonatal
Facial Coding System in pain assessment of premature neonates. Pain 76:277–286
Hain RGW (1997) Pain scales in children: review. Palliat Med 11:341–350
H€am€al€ainen ML, Hoppu K, Santavuori P (1997) Sumatriptan for migraine attacks in children: a
randomized placebo-controlled study. Do children with migraine respond to oral sumatriptan
differently from adults? Neurology 48:1100–1103
Haworth SG, Beghetti M (2010) Assessment of endpoints in the pediatric population: congenital
heart disease and idiopathic pulmonary arterial hypertension. Curr Opin Pulm Med 16(Suppl 1):
S35–S41
International Conference for Harmonisation (1997) General considerations for Clinical Trials E 8
International Conference for Harmonisation (2001) Clinical investigation of medicinal products in
the paediatric population E 11. CPMP/ICH/2711/99
International Headache Society Headache Classification Subcommittee (2004) International

classification of headache disorders, 2nd edition. Cephalgia 24(Suppl 1):9–160
Inwald DP, Tasker RC, Peters MJ, on behalf of the Paediatric Intensive Care Society Study Group
(PIGS-SG) (2009) Emergency management of children with severe sepsis in the United
Kingdom: the results of the Paediatric Intensive Care Society sepsis audit. Arch Dis Child
94:348–353
Jacobson S (2007) Common medical pains. Paediatr Child Health 12:105–109
Lesko JJ, Atkinson AJ Jr (2001) Use of biomarkers and surrogate endpoints in drug development
and regulatory decision making: criteria, validation, strategies. Annu Rev Pharmacol Toxicol
41:347–366
Lewis DW, Winner P, Wasiewski W (2005) The placebo responder rate in children and
adolescents. Headache 45:232–239
Lewis DW, Paul Winner P, Hershey AD, Warren W, Wasiewski WW, on behalf of the Adolescent
Migraine Steering Committee (2007) Efficacy of zolmitriptan nasal spray in adolescent
migraine. Pediatrics 120:390–396
Li AM et al (2005) The six-minute walk test in healthy children: reliability and validity. Eur Respir
J 25:1057–1060
Li JS, Benjamin DK Jr, Severin T, Portman RJ (2010) Paediatric anti-hypertensive clinical trials
and various factors influencing trial success or failure. In: Rose K, van den Anker JN (eds)
Guide to paediatric drug development and clinical research. Karger, Basel, pp 196–205
Loizzo A, Stefano Loizzo S, Capasso A (2009) Neurobiology of pain in children: an overview.
Open Biochem J 3:18–25
López A, Lorente JA, Steingrub J, Bakker J, McLuckie A, Willatts S, Brockway M, Anzueto A,
Holzapfel L, Breen D, Silverman MS, Takala J, Donaldson J, Arneson C, Grove G, Grossman S,
Grover R (2004) Multiple-center, randomized, placebo-controlled, double-blind study of the
nitric oxide synthase inhibitor 546C88: effect on survival in patients with septic shock. Crit Care
Med 32:21–30
Madriago E, Silberbach M (2010) Heart failure in infants and children. Pediatr Rev 31(1):4–11
McGrath PJ, Walco GA, Turk DC, Dworkin RH, Brown MT, Davidson K, Eccleston C, Finley GA,
Goldschneider K, Haverkos L, Hertz SH, Ljungman G, Palermo T, Rappaport BA, Rhodes T,
Schechter N, Scott J, Sethna N, Svensson OK, Stinson J, von Bayer CL, Walker L, Weisman S,
White RE, Zajick A, Zeltzer L (2008) Core outcome domains and measures for pediatric acute
and chronic/recurrent pain clinical trials: PedIMMPACT recommendations. J Pain 9:771–783
Merkel SI, Voepel-Lewis T (1997) The FLACC: a behavioural scale for scoring postoperative pain
in young children. Pediatr Nurs 23:293–297
Merskey H, Bogduk N (eds) (1994). Part III: pain terms, a current list with definitions and notes on
usage. In: Classification of chronic pain, 2nd edn. IASP Task Force on Taxonomy. IASP Press,
Seattle WA, pp 209–214
Molenberghs G, Orman C (2009) Surrogate endpoints: application in pediatric clinical trials. In:
Mulberg A, Silber S, vand der Acker JN (eds) Pediatric drug development, concepts and
applications. Wiley-Blackwell, Hoboken, NJ, pp 501–511
Mortimer MJ, Kay J, Jaron A (1992) Childhood migraine in general practice: clinical features and
characteristics. Cephalgia 12:238–253
Nilsson S, Finnstr€om B, Kosinky E (2008) The FLACC behavioural scale for procedural pain
assessment in children aged 5–16 years. Pediatr Anesth 18:767–774
Odetola FO, Gebremariam A, Freed GL (2007) Patient and hospital correlates of clinical outcomes
and resource utilization in severe pediatric sepsis. Pediatrics 119:487–494
Paediatric Research Equity Act (2003) Public Law No 108–155
Puntman VO (2009) How-to guide on biomarkers: biomarker definitons, validation and
applications with examples from cardiovascular disease. Postgrad Med J 85:538–545
Redmond C, Colton T (eds) (2001) Biostatistics in clinical trials, Wiley reference series in
biostatistics., p 322, Outcome measure
Regulation (EC) (2006) No 1901/2006 On medicinal products for paediatric use
Regulation (EC) No 726/2004 (2004) On conditional approval of medicinal products

Rosenfeld M (2007) An overview of endpoints for cystic fibrosis clinical trials: one size does not
fit all. Proc Am Thorac Soc 4:299–301
Ross RD, Bollinger RO, Pinsky WW (1992) Grading the severity of congestive heart failure in
infants. Pediatr Cardiol 13(2):72–75
Rothman M, Kleinman L (2009) Patient-reported outcomes in paediatric drug development. In:
Mulberg A, Silber S, der Acker JN (eds) Pediatric drug development, concepts and
applications. Wiley-Blackwell, Hoboken, NJ, pp 513–524
Rothner AD, Wasiewski W, Winner P, Lewis D, Stankowski J (2006) Zolmitriptan oral tablet in
migraine treatment: high placebo responses in adolescents. Headache 46:101–109
Ruperto N, for the Pediatric Rheumatology International trials Organisation (PRINTO) and the
Pediatric Rheumatology Collaborative Study Group (PRCGS) et al (2006) The pediatric rheuma-
tology international trials organization/American college of rheumatology provisional criteria for
the evaluation of response to therapy in juvenile systemic lupus erythematosus: prospective
validation of the definition of improvement. Arthritis Rheum (Arthritis Care Res) 55(3):355–363
Shaddy RE, for the Pediatric Carvedilol Study Group et al (2007) Carvedilol for children and
adolescents with heart failure. JAMA 298(10):1171–1179
Sinha I, Jones L, Smyth RL, Williamson PR (2008) A systematic review of studies that aim to
determine which outcomes to measure in clinical trials in children. PLoS Med 5:e96
Slater R, Cantarella A, Franck L, Meek J, Fitzgerald M (2008) How well do clinical pain
assessment tools reflect pain in infants? PLoS Med 6:e129
Stanford EA, Chambers CT, Graig KD (2006) The role of developmental factors in predicting
young children’s use of self-report scale for pain. Pain 120:16–23
Stevens B, Johnston C, Petryshen P, Taddio A (1996) Premature infant pain profile: development
and initial validation. Clin J Pain 12:13–22
Stinson JN, Kabanagh T, Yamada J, Gill N, Stevens B (2006) Systematic review of the psycho-
metric properties, interpretability and feasibility of self-report pain intensity measures for use
in clinical trials in children and adolescents. Pain 125:143–157
The International Chronic Granulomatous Disease Cooperative Study Group (1991) A controlled
trial of interferon gamma to prevent infection in chronic granulomatous disease. N Engl J Med
324:509–516
Tugwell P, Boers M (1993) OMERACT conference on outcome measures in RA clinical trials:
introduction. J Rheumatol 20:528–530
University of Liverpool (2010) Core Outcome Measures in Effectiveness Trials (COMET). http://
www.liv.ac.uk/nwhtmr/comet/comet.htm
van Dijk M, de Boer JB, Koot HM, Tibboel D, Passchier J, Duivenvoorden HJ (2000) The
reliability and validity of the COMFORT scale as a postoperative pain instrument in 0 to 3
year-old infants. Pain 84:367–377
Varni JW, Seid M, Rode CA (1999) The PEdsQL: measurement model for the Pediatric Quality of
Life Inventory. Med Care 37:126–139
Varni JW, Seid M, Kurtin PS (2001) PedQL 4.0: reliability and validity of the Pediatric Quality of
life Inventory version 4.0 generic core scales in healthy and patient populations. Med Care
39:800–812
Vincent JL (2004) Endpoints in sepsis trials. More than just 28 day mortality? Crit Care Med 32
(Suppl):S209–S213
von Baeyer CL, Spagrud LJ (2007) Systematic review of observational (behavioral) measures of
pain for children and adolescents aged 3 to 18 years. Pain 127:140–150
von Baeyer CL, Spagrud LJ, McCormick JC, Choo E, Neville K, Connelly MA (2009) Three new
datasets supporting the use of the Numerical Rating Scale (NRS-11) for children’s self-reports
on pain intensity. Pain 143:223–227
Walco GA, Conte PM, Labay LE, Engel R, Zeltzer LK (2005) Procedural distress in children with
cancer: self-report, behavioral observations, and physiological parameters. Clin J Pain
21:484–490
Walco G, Dworkin RH, Krane EJ, LeBel AA, Treede R-D (2010) Neuropathic pain in children:
special considerations. Mayo Clin Proc 85(Suppl):S33–S41
Walker SM (2008) Pain in children: recent advances and ongoing challenges. Br J Anaesth
101:101–110
Watson RS, Carcillo JA (2005) Scope and epidemiology in pediatric sepsis. Pediatr Crit Care Med
6(Suppl):S3–S5
Watson D, Grover R, Anzueto A, Lorente J, Smithies M, Bellomo R, Guntupalli K, Grossman S,
Donaldson J, Glaxo Wellcome International Septic Shock Study Group (2004) Cardiovascular
effects of the nitric oxide synthase inhibitor NG-methyl L-arginine hydrochloride (546C88) in
patients with septic schock: results of a randomized, double-blind, placebo-controlled multi-
center study (study no 144–002). Crit Care Med 32:13–20
Winner P, Linder SL, Lipton RB, Almas M, Parsons B, Pitman V (2007) Eletriptan for acute
treatment of migraine in adolescents: results of a double-blind placebo-controlled trial. Head-
ache 47:511–518
Safety Assessment in Pediatric Studies
Gideon Koren, Abdelbasset Elzagallaai, and Fatma Etwel
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
2 Pharmacoepidemiological Approaches . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 170
3 Pemoline-Index Case . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 171
3.1 Pediatric ALF Cases Receiving Pemoline and Reported to the FDA . . . . . . . . . . . . . . 173
3.2 Calculating Relative Risk of Pemoline Associated with ALF . . . . . . . . . . . . . . . . . . . . . . 173
4 Laboratory-Based Methods of Predicting Serious Adverse Reactions in Children . . . . . . 174
4.1 The Lymphocyte Transformation Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 175
4.2 The Lymphocyte Toxicity Assay . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 176
4.3 The LTA in the Diagnosis of AHS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 178
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 179
Abstract It typically takes many years before an association of a drug with a rare,
serious adverse reaction is established. As related to pediatric drug use, evidence is
even more erratic, as most drugs are used off labels. To enhance child safety, there
is an urgent need to develop robust and rapid methods to identify such associations
in as timely a manner as possible. In this chapter, several novel methods, both
clinically based pharmacoepidemiological approaches and laboratory-based methods,
are described.
Keywords Adverse drug reactions • Children • Neonates • Side effects
G. Koren (*)
The Motherisk Program, Division of Clinical Pharmacology and Toxicology, Hospital for Sick
Children, University Avenue 555, Toronto M5G 1X8, ON, Canada
e-mail: gidiup_2000@yahoo.com
A. Elzagallaai • F. Etwel
Division of Clinical Pharmacology and Toxicology, Hospital for Sick Children,
University Avenue 555, Toronto M5G 1X8, ON, Canada

170 G. Koren et al.
1 Introduction
Each year prescription drugs cause fatal adverse drug reactions (ADR) to 100,000
individuals in the USA, making prescription drugs between the fourth and sixth
leading cause of death, after heart disease, cancer, stroke, pulmonary disease, and
accidents (Lazarou et al. 1998).
Before a pharmaceutical product is marketed, the manufacturer must prove that it is
both effective and safe by performing extensive studies in animals and in human
clinical trials. However, premarketing studies cannot guarantee product safety as they
are limited by the small numbers of patients (between 1,000 and 3,000 subjects).
Importantly, serious ADRs (e.g., agranulocytosis) occur at a rate of between 1:1,000
and 1:10,000 patients. Additionally, clinical trials typically exclude vulnerable
populations such as pregnant women, children, elderly people, those with complicated
diseases, or those taking other medications. Hence, uncommon adverse effects,
delayed effects, or consequences of long-term drug administration often are not
observed before the drug has been marketed (Stricker and Psaty 2004). While the
more common type A ADRs (reactions that are an augmentation of the normal
pharmacological actions of the drug) may already have been identified by the time
of licensing (Pirmohamed et al. 1998), type B ADRs (idiosyncratic or bizarre reactions
that cannot be predicted from the known pharmacology of the drug) will only be
detected after licensing through postmarketing surveillance (Meyboom et al. 1997).
Postmarketing studies are based on collecting spontaneous case reports of
ADRs. There are two systems where clinical observers can use to address their
voluntary reporting of ADRs. The first is the published medical literature, which is
a highly efficient warning system for new adverse reactions, and often recognizes
rare events and people at high risk (Begaud et al. 1994). The second consists of
national and international adverse drug reaction monitoring centers, such as the
Food and Drug Administration (FDA). In the USA, the FDA started a voluntary
reporting system in the late 1960s, receiving reports from health care providers,
consumers, and pharmaceutical companies. Unlike health care providers and
consumers, the manufacturers have a regulated duty to report to the FDA on any
ADR. The system had been criticized in the 1970s for its delay in sending reports of
the newly identified ADRs to the Physicians Desk Reference (Zielinskin 2005). The
FDA system is probably overwhelmed by ADR reports from all interested parties,
as the experts at the Agency have insufficient time to analyze all incoming reports
in depth. Moreover, the FDA does not have the regulated authority to mandate drug
manufacturers to conduct directed postmarketing surveillance studies (Millichap
1976), which could help in detecting uncommon serious ADRs.
2 Pharmacoepidemiological Approaches
Over the last few years, we have developed a novel detection method to allow
regulatory agencies and manufacturers to create a rapid signal for an association
between the drug and the corresponding ADRs, in the postmarketing period. This
Safety Assessment in Pediatric Studies 171
method can allow early identification of rise in the incidence rate of severe organ
failure associated with the medication. This method can help to protecting the
public from unexpected harmful effects of new drugs. Herein, we will use the
pemoline-associated acute liver failure (ALF) as a model for the development of
this novel system.
3 Pemoline-Index Case
Pemoline (phenylisohydantoin, Cylert™) is a mild central nervous system stimu-

lant that has been approved in 1975 for children with attention-deficit hyperactivity
disorder (ADHD) (Stevenson and Wolraich 1989; Berkovitch et al. 1995). In 1995,
we reported the case of a 14-year-old boy diagnosed with ADHD (Berkovitch et al.
1995) who had been previously healthy and had received concomitant pemoline,
37.5 mg a day, for 16 months and methylphenidate, 20 mg a day for 2 months, to
control his symptoms. He was hospitalized due to jaundice, which progressed into
ALF. A liver biopsy was suggestive of drug toxicity. He underwent liver transplant
which failed and the child died. All known causes of liver failure were ruled
out including infection, metabolic disease, tumor, or chemicals. We found two
previous published fatal cases due to ALF associated with pemoline both from the
USA. At that time, the USA, FDA, and the manufacturer were not aware of
additional cases. We estimated that a child receiving pemoline has a relative risk
of development of liver failure of 45.3 (95% confidence interval, 4.1–510) and
urged others to report on similar cases. This highly significant association
(p < 0.001) suggested causation. After this report, other investigators around the
world reported more cases of liver failure associated with pemoline. A black box
warning was added to the labeling in the USA in December 1996, and a “Dear
Doctor” letter was mailed out by the manufacturer to all US physicians to use the
drug as a last resort, but physicians continued to use pemoline as a first-line therapy.
In September 1999, Health Canada withdrew pemoline from the Canadian market
(more cases of pemoline liver toxicity were reported, and pressure on the FDA
increased to ban the drug). In May, 2005, the manufacturer chose to stop sales and
marketing of Cylert™ in the US Cylert™ would remain available through
pharmacies and wholesalers until supplies are exhausted; no additional product
would be available. In November 2005, pemoline was finally removed from the US
market.
From these events, it is evident that there was a 25-year delay in identifying
pemoline-associated ALF, leading to a delay in withdrawing the drug from the
market and putting children at risk for fatal drug-related injury.
We hypothesized that using available data one could predict pemoline-
associated ALF several years after its marketing, without the protracted delay of
25 years.
The study was a postmarketing surveillance of pemoline hepatotoxicity based on
cases reported to either the FDA and/or in the medical literature. The population for
172 G. Koren et al.
the study consisted of children in the USA and Canada. For each calendar year after
1975 when pemoline was approved to be marketed as a treatment for ADHD, the
number of children who were on pemoline was estimated as was the number of
reported cases of ALF associated with pemoline.
After obtaining the yearly number of children on pemoline and the yearly
number of children who developed ALF while on pemoline, a comparison was
made between these data and the background incidence rate of idiopathic ALF in
children in the general population. This comparison was made year by year to
define the earliest year when the rate of serious ALF due to pemoline was signifi-
cantly higher than predicted in the general population.
Data were synthesized from systematic review of the published literature. Only
studies calculating the rate of ALF in children and their etiologies, including
idiopathic liver failure, were included.
Information regarding the number of children on pemoline in Canada per year
was obtained from IMS (International Medical Statistics, Montreal Quebec). The
IMS is a holder of statistical medical information that can be accessed by
researchers, academics, and government. For US data, we gathered the information
by synthesizing available published data, by systematic review of Medline
EMBASE and Scopus, and by obtaining all articles that reported on the number
of children prescribed pemoline.
The annual number of children on pemoline in the USA and Canada who
developed ALF was obtained from the FDA under the Freedom of Information
Act. All pemoline cases reported to the FDA between 1975 and 1999 were
analyzed. The criteria for selection of liver injury cases were age between 0 and
18 years, any report of irreversible damage to the liver, and children who received
the dose schedule recommended for its primary indication. We excluded cases
reporting increased liver enzyme levels that returned to normal once pemoline was
discontinued. Some of these cases have also been published in the literature and
articles were obtained. We used the same criteria for selection of the literature cases
as was used in the FDA cases. All the published cases were subjected to causality
assessment using the Naranjo ADR probability Scale (Naranjo et al. 1981). The
Naranjo ADR probability scale is a tool widely used to determine the likelihood
that an ADR is caused by the implicated medication. Ten questions are answered
and assigned a weighted score of +2 to 2. Where there were insufficient data
available, the particular question receives a score of 0. Based on the Naranjo criteria
15, each case is scored between (<1 and >9) and assigned a likelihood of causing
an ADR from doubtful, possible, probable, to highly probable.
Based on a recent large comprehensive study of fulminant hepatic failure,
approximately 230 children are estimated to be afflicted each year in the USA
(Liu et al. 2001). The number of children who lived in the USA has been estimated
at 73,043,506 (Children Defense fund), and hence the overall rate of ALF in
children is estimated at 1:300,000.
Based on all available studies, 16% of the cases of ALF were due to unknown
reasons (idiopathic). Hence, we estimated that the rate of idiopathic liver failure in
North American children is 1:2,000,000.
We identified all papers that surveyed the prevalence of medication use to treat
children with ADHD in the USA and they were used to calculate the yearly number
of American school children on ADHD medication from 1975 through 1993. For
any missing year for which no publication was available, we calculated the mean
value from the closest years before and after. The percentage of children receiving
treatment with stimulant medication for ADHD ranged between 2.1 and 6%. The
percentage of reported pemoline use among ADHD children was 1% in 1975 and
increased gradually to 6% in 1987. Between 1987 and 1993, there was no data
available on the percentage of pemoline use among ADHD children, so we assumed
that the percentage was not changed since 1987. The overall number of school
children in the USA was obtained from international statistics. Based on the above
number, we estimated the number of children taking pemoline in the USA.
We estimated that a total of 45,404 Canadian children years were treated with
pemoline from 1978 to 2004. In Canada, the marketing of pemoline started only in
the 1980s. The Canadian Drug Identification Codes are drug product database
books published annually. The first time pemoline was included in these databases
was in 1981 (the first time pemoline was included in the Compendium of
Pharmaceuticals and Specialties was in 1986) (Canadian Pharmaceutical Associa-
tion and Canadian Pharmacists Association 1986).
3.1 Pediatric ALF Cases Receiving Pemoline and Reported

to the FDA
Thirty cases of children who were on pemoline therapy and who developed
irreversible ALF were reported to the FDA. The first case was in 1977.
3.2 Calculating Relative Risk of Pemoline Associated with ALF
Using the FDA reports, each year after introducing pemoline the relative risk of
children on pemoline developing ALF was high, ranging between 9.12 and 24.08.
The highest RR was detected in 1978. All these RR were statistically significant
(Etwel et al. 2008).
Using pemoline as a model, we were able to show that employing existing data
at the time one could estimate the incidence rate of serious ADRs early in the
marketing cycle.
Hence, as early as 1978, a significant signal existed indicating that pemoline is
associated with ALF, 16 years before the first published suggestion by Berkovitch
and colleagues (1995), 22 years before removal of the medication from the
Canadian market, and 28 years before removal from US market. While we present
analysis related to ALF, similar population-based statistics are available for all
other adverse events, from agranulocytosis to pulmonary fibrosis. This method
174 G. Koren et al.
should enable researchers, clinicians, drug companies, and regulators to identify

uncommon adverse drug reactions, associated with new medications, earlier in the
course of marketing and thus quantify serious ADRs and identify patient
populations at special risk.
4 Laboratory-Based Methods of Predicting Serious

Adverse Reactions in Children
The concept of developing laboratory tests that can predict rare, but potentially
fatal, adverse drug reactions is ideally exemplified in the case of the anticonvulsant
hypersensitivity syndrome (AHS).
We will review critically the usefulness of available in vitro tests in the diagnosis
of AHS.
Anticonvulsant hypersensitivity syndrome (AHS), also known as drug hyper-
sensitivity syndrome or drug rash with eosinophilia and systemic symptoms
(DRESS), is a type B (“bizarre”) adverse drug reaction (ADR) that develops in
susceptible patients following exposure to certain drugs, including aromatic
anticonvulsants (Shear and Spielberg 1988; Zaccara et al. 2007) Although lacking
a defined clinical picture, AHS is typically associated with the development of skin
rash, fever, and internal organ dysfunction that may include blood dyscrasias,
hepatitis, nephritis, myocarditis, thyroiditis, and interstitial pneumonitis and
encephalitis (Peyriere et al. 2006). The pathophysiological mechanisms underlying
AHS are not well understood; however, it is believed to be immune mediated in
general and involve generation of electrophilic reactive metabolites that react
covalently with macromolecules to form immunogenic adducts able to activate
the immune system (Shapiro and Shear 1996; Spielberg et al. 1981a, b). The
accurate incidence of AHS is unknown due to underreporting, but it has been
estimated to range from 1 in 1,000 to 1 in 10,000 in patients newly exposed to
aromatic anticonvulsants (Tennis and Stern 1997). While the disorder is rare, it is
potentially fatal and represents a clinical dilemma to treating doctors. Diagnosis of
AHS is challenging, as a reliable and safe diagnostic test is not available to confirm
causality or identify the culprit drug. A number of in vivo and in vitro tests have
been devised and used to aid the diagnosis of AHS. These include skin tests (patch
test, prick test, and intradermal test), the lymphocyte transformation test (LTT), and
the lymphocyte toxicity assay (LTA) (Pourpak et al. 2008).
In vitro diagnostic tests have the advantage over in vivo tests (patch test and
rechallenge) of bearing no potential harm to patients. A number of in vitro diagnos-
tic tests have been used to aid the diagnosis of delayed-type drug hypersensitivity
reactions (Naranjo et al. 1992; Beeler and Pichler 2007; Lan et al. 2006); however,
their true value is yet to be defined. Among these tests are those that utilize
peripheral blood mononuclear cells (PBMCs) as target cells, including the LTT
and the LTA. Unfortunately, these techniques require expensive equipment and
sophisticated laboratories as well as specialized experience with biochemical and
molecular methods, so only a few centers are sufficiently equipped to perform them.
Hence, these methods, although successfully employed as research tools, have not
been successfully translated into diagnostic tests (Wu et al. 2006; Beeler et al. 2006).
Leukocytes are present in peripheral blood at densities of 5–7 103 cells/mm3;
20–50% of these cells are lymphocytes, whereas 2–10% are monocytes.
Lymphocytes are favored as a model for investigation of immune-mediated
diseases because of their unique characteristics, which include that (1) they are
easily obtained at adequate density; (2) they play a key role in the immune system
by orchestrating different elements of the immune response and thus represent the
state of the immune system in the specific patient; (3) they are metabolically active
and express most of the enzymes required for drug detoxication; and (4) individual
genetically based defects in the expression or activity of these detoxication
enzymes are phenotypically expressed in lymphocytes.
4.1 The Lymphocyte Transformation Test
The in vitro lymphocyte transformation phenomenon was first described during the
late 1950s. In short, human peripheral blood leukocytes (PBLs) differentiate in
short-term primary cultures, forming plasts. This effect was later attributed to the
presence of a constituent [phytohemagglutinin (PHA)] of a plant extract from red
kidney beans (Phaseolus vulgaris) that is used to isolate blood peripheral leukocytes
(Rigas and Osgood 1955). PHA causes erythrocytes to aggregate and sediment,
allowing leukocytes to separate from whole blood preparations. In a later report,
Nowell (1960) demonstrated that PHA also initiates mitotic activity (transforma-
tion) in cultured human leukocytes. To show that lymphocyte behavior in vitro has
an immunological basis, Pearmain et al. (1963) exposed PBLs isolated from both
tuberculin-sensitive and tuberculin-nonsensitive patients to tuberculin in vitro. Only
PBLs from tuberculin-sensitive patients showed mitotic activity, whereas cells from
patients not previously exposed to the antigen showed no mitosis.
One of the first reports of using the LTT for diagnosis of drug allergy was by
Holland and Mauer (1964) who evaluated the effect of phenytoin on cultured
lymphocytes isolated from patients sensitive to the drug and nonsensitive (control)
subjects. In these experiments, PHA used as a positive control showed nonspecific
stimulation of all cells sampled, whereas phenytoin stimulated only the cells from
phenytoin-sensitive patients. When tested with peripheral lymphocytes isolated
from a sulfadiazine-sensitive patient and incubated with the culprit drug in vitro,
this effect was found to be concentration-dependent.
The procedure includes incubation of PBMCs isolated from drug-hypersensitive
patients with the incriminated agent at nontoxic concentrations and observation
of any increase in the rate of cell proliferation measured by [3H]thymidine
incorporation. The increase in cell proliferation is expressed as a ratio between
proliferation of cells incubated with and without the drug (vehicle alone; control).
This ratio is defined as the stimulation index (SI) and it is calculated as follows (1):
176 G. Koren et al.
½3 H thymidine uptake in the presence ofthedrug

SI ¼ (1)
½3 H thymidine uptake in the absense of the drug
where [3H]thymidine uptake is expressed in counts per minute.

Cell cultures from drug-exposed and unexposed nonsensitive individuals are
also used to confirm the specificity of a potential drug effect. The final result of the
test depends on several factors such as the value of background cell proliferation
and the type of the drug; however, an SI of >3 is always considered indicative of a
positive reaction. Other end points for measurement of T-cell activation, such as
elevation of released cytokines (using an enzyme-linked immunosorbent assay
[ELISA]), have been proposed and could be a more sensitive method for detection
of T-cell activation than measurement of the rate of cell proliferation.
The LTT has been used by some investigators for diagnosis of potential drug
allergy cases for more than 20 years. However, its value in diagnosis and prediction
of AHS remains controversial.
4.2 The Lymphocyte Toxicity Assay
Introduced by Spielberg and colleagues (1980), the LTA is an in vitro test that
utilizes isolated PBMCs to investigate the mechanistic pathogenesis of idiosyn-
cratic drug reactions. The test is based on the hypothesis that drug hypersensitivity
develops as a result of imbalance between generation of toxic reactive metabolites
(metabolic activation or toxication) and detoxication capacity that leads to accu-
mulation of toxic metabolites (the “reactive metabolite” hypothesis). In this test,
lymphocytes are used not as immunogenic cells but rather as easy-to-obtain surro-
gate target cells. The procedure of the test entails incubation of PBMCs isolated
from the patient with the culprit drug in the presence of Phenobarbital-induced
mouse, rat, or rabbit liver microsomal 19,000 g supernatant fraction (S9), as a
source of cytochrome P450 (CYP) mono-oxygenase activity.
CYP activity in the rodent (or sometimes human) liver preparation is
hypothesized to oxidize drug to its active (cytotoxic) metabolite(s). Lymphocytes
contain enzymes that are required for drug detoxication, including epoxide
hydrolases and glutathione S-transferases, and any genetic defect in the function
of these enzymes is phenotypically expressed in these cells. The percentage of cell
death is then determined using different methods for assessing cell death [e.g.,
trypan blue exclusion or with a tetrazolium dye; for example, by the MTT (3-(4,5-
dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) method]. Cell death is
assumed to reflect the vulnerability of the cells to the toxic effects of the drug,
which is hypothesized to indicate the susceptibility of the patient to develop
hypersensitivity reactions to the parent drug and its reactive metabolite(s), presum-
ably via differences in detoxication capacity and immune processing.
Aromatic anticonvulsants are excellent examples of metabolically activated
cytotoxicants, metabolized primarily by hepatic CYP isozymes into reactive
electrophilic arene oxide metabolites (Begaud et al. 1994). These unstable and
highly reactive intermediate metabolites are readily detoxified by epoxide hydro-
lase and/or glutathione S-transferase enzymes, usually to non-electrophilic products
(dihydrodiols and S-glutathione conjugates, respectively).
Although the same cell model (isolated PBMCs) is used in both types of assay,
LTT and LTA are completely different approaches to the diagnosis of AHS.
Whereas the former detects the in vivo immunological generation of drug-specific
T lymphocytes used as a sign of hypersensitivity, the latter detects genetic defects
that lead to accumulation of toxic metabolites, which are assumed to be a major
factor in the etiology of drug hypersensitivity in addition to possible differences in
cell death. Because the two tests use the same cell model and have similar
nomenclature, it is not uncommon for individuals to confuse the LTT for the
LTA or vice versa, or to use different nomenclature to describe these tests.
Retrieved publications were manually reviewed and the following selection
criteria were applied: (1) original article written in English; (2) study performed
in human subjects; (3) LTA or LTT used to diagnose AHS due to one or more
aromatic anticonvulsant drug(s); and (4) sufficient technical data for scientific
evaluation.
Thirty-one articles from PubMed, 22 articles from MED-LINE, and 28 from
EMBASE were found that met our selection criteria. The search results from the
three databases were then combined and duplicates were removed. The final
number of included articles from the three databases was 48. Thirty-six articles
used the LTT and 12 used the LTA for the diagnosis of AHS (Figure 4). Although
single case reports were included in the review, none of these reports were used to
calculate any of the tests’ epidemiological characteristics.
In the systematic review we have conducted recently its use was almost always
confined to experienced technicians in well-equipped research centers, primarily
for the purpose of investigating the mechanism of T-cell-mediated reactions rather
than diagnosis of drug allergy (Elzagallaai et al. 2009). In addition, because of its
low laboratory-to-laboratory reproducibility and difficulty in evaluating results, this
test cannot be described as user friendly and requires a great deal of experience for
interpretation of results. For this reason, the test has not been translated into
widespread clinical use. In fact, only a few research groups worldwide use this
technique routinely.
In an attempt to determine the sensitivity and specificity of the LTT in the
diagnosis of allergy to different drugs, the files of 923 patients with possible
hypersensitivity reactions to drugs were studied. These patients were classified
based on their medical history, follow-up, and provocation tests into four groups
where drug allergies were “definite,” “probable,” “less probably,” or “negative.”
One hundred cases were considered to have a very high probability of drug allergy,
of which 78 had a positive LTT. Only three of these 100 cases were attributed to
anticonvulsants (2 to carbamazepine and 1 to phenytoin). The two carbamazepine
cases exhibited positive LTTs, whereas for the phenytoin case, the LTT was
negative. Although the chemistry of the drug in question appears to play a major
role in determining the usefulness of the LTT, the overall specificity and sensitivity
178 G. Koren et al.
of this test in this study were found to be in the range of 85 and 76%, respectively. It
is not known whether or not these numbers can be applied to anticonvulsant drugs.
However, because many different factors are involved in determining the final
result of the LTT as discussed below, one cannot generalize these figures to include
all types of drugs taken under various conditions.
Numerous factors have been found to affect the predictive value of the LTT
in the diagnosis of drug hypersensitivity reactions. These factors include the
timing of the test in relation to the beginning of the reaction, the type of clinical
manifestations cause by the drug, the nature of the suspected drug, and the test
procedure itself.
4.3 The LTA in the Diagnosis of AHS
The use of the LTA in diagnosing AHS dates back to the early 1980s. However, the
lack of large-scale application is quite obvious. Shear and Spielberg (1988) studied
53 patients with a medical history suggesting AHS due to phenytoin, carbamaze-
pine, or phenobarbital, as well as 49 unexposed healthy controls and 10 phenytoin-
exposed healthy controls. Symptoms include fever, skin rash (varying in severity
from generalized exanthema to TEN), eosinophilia, atypical lymphocytosis, and
internal organ involvement (liver, kidney, thyroid, or lung). The performance of the
LTA as a diagnostic test in this cohort of patients was excellent, with only two false
positives and one false negative result in patients with hypersensitivity reactions to
phenobarbital.
AHS is a rare but potentially lethal disorder. One of the most challenging aspects
of this disease is the difficulty of establishing a solid diagnosis in a timely manner.
Lack of a diagnosis or misdiagnosis may result in increased morbidity, increased
mortality, and extended hospitalization. Between 10 and 27% of patients with
epilepsy discontinue their first antiepileptic drug because of the development of
adverse reactions (Kwan and Brodie 2001). Aromatic anticonvulsant drugs such as
phenytoin, carbamazepine, phenobarbital, and lamotrigine are linked to a relatively
high risk of development of hypersensitivity reactions. Carbamazepine was found
to be the most common cause of severe forms of AHS (i.e., SJS and TEN).
The diagnosis of AHS entails two main processes: first, establishing the diagno-
sis of the hypersensitivity reaction, usually from a series of clinically similar
differential diagnoses; and second, identifying the culprit drug, potentially among
a number of other concomitantly prescribed, innocent drugs. Numerous diagnostic
tests are available and have been attempted for the diagnosis of drug hypersensitiv-
ity reactions; however, their epidemiological qualities are dependent on the type of
reaction (immediate vs. delayed reactions) and type of drug, and choosing the best
test for a specific drug or drug class can be challenging.
The sensitivity and specificity of the LTT in the diagnosis of drug allergy have
been estimated to range from 56 to 78% and from 85 to 93%, respectively, although
these estimates are generally based on cases of allergy to b-lactam antibacterials
and cannot be extended to other types of drugs. In the diagnosis of AHS due to
aromatic anticonvulsants, the LTT has frequently shown a sensitivity between 71
and 100%, but this also ranges as low as 19–40%.
Combined use of pharmacoepidemiological approaches and biological markers
is needed to improve the ability to predict adverse drug reactions in children and
prevent severe morbidity and mortality.
References
Beeler A, Pichler WJ (2007) In vitro tests of T-cell-mediated drug hypersensitivity. In: Pichler WJ (ed)
Drug hypersensitivity. Karger, Basel, pp 380–390
Beeler A, Engler O, Gerber BO et al (2006) Long-lasting reactivity and high frequency of drug-
specific T cells after severe systemic drug hypersensitivity reactions. J Allergy Clin Immunol
117:455–462
Begaud B, Moride Y, Tubert-Bitter P, Chaslerie A, Haramburu F (1994) False-positives in
spontaneous reporting: should we worry about them? Br J Clin Pharmacol 38:401–404
Berkovitch M, Pope E, Phillips J, Koren G (1995) Pemoline-associated fulminant liver failure:
testing the evidence for causation. Clin Pharmacol Ther 57:696–698
Canada (1981) Drugs Directorate. Canadian Drug Identification Code
Canadian Pharmaceutical Association and Canadian Pharmacists Association (1986) Compen-
dium of pharmaceuticals and specialties. Canadian Pharmaceutical Association, Toronto
Elzagallaai AA, Knowles SR, Rieder MJ, Bend JR, Shear NH, Koren G (2009) In vitro testing for
the diagnosis of anticonvulsant hypersensitivity syndrome. Mol Diagn Ther 13:313–330
Etwel FA, Rieder MJ, Bend JR, Koren G (2008) A surveillance method for the early identification
of idiosyncratic adverse drug reactions. Drug Saf 31:169–180
Holland P, Mauer AM (1964) Drug-induced in-vitro stimulation of peripheral lymphocytes.
Lancet 1:1368–1369
Kwan P, Brodie MJ (2001) Effectiveness of first antiepileptic drug. Epilepsia 42:1255–1260
Lan CC, Wu CS, Tsai PC et al (2006) Diagnostic role of soluble fas ligand and secretion by
peripheral blood mononuclear cells from patients with previous drug-induced blistering
disease: a pilot study. Acta Derm Venereol 86:215–218
Lazarou J, Pomeranz BH, Corey PN (1998) Incidence of adverse drug reactions in hospitalized
patients: a meta-analysis of prospective studies. J Am Med Assoc 279:1200–1205
Liu E, Dobyns E, Narkewicz M (2001) Acute hepatic failure in children: a seven year experience at
a children’s hospital. Hepatology 34:197A
Meyboom RH, Egberts AC, Edwards IR, Hekster YA, de Koning FH, Gribnau FW (1997)
Principles of signal detection in pharmacovigilance. Drug Saf Int J Med Toxicol Drug Exp
16:355–365
Millichap JG (1976) The hyperactive child. Practitioner 217:61–65
Naranjo CA, Busto U, Sellers EM (1981) A method for estimating the probability of adverse drug
reactions. Clin Pharmacol Ther 30:239–245
Naranjo CA, Sher NH, Lanctot KL (1992) Advances in the diagnosis of adverse drug reactions.
J Clin Pharmacol 32:897–904
Nowell PC (1960) Phytohemagglutinin: an initiator of mitosis in cultures of normal human
leukocytes. Cancer Res 20:4
Pearmain G, Lycette RR, Fitzgerald PH (1963) Tuberculin-induced mitosis in peripheral blood
leucocytes. Lancet 1:637–638
Peyriere H, Dereure O, Breton H et al (2006) Variability in the clinical pattern of cutaneous side-
effects of drugs with systemic symptoms: does a DRESS syndrome really exist? Br J Dermatol
155:422–433
180 G. Koren et al.
Pirmohamed M, Breckenridge AM, Kitteringham NR, Park BK (1998) Fortnightly review:

adverse drug reactions. Br Med J 316:1295–1298
Pourpak Z, Fazlollahi MR, Fattahi F (2008) Understanding adverse drug reactions and drug
allergies: principles, diagnosis and treatment aspects. Recent Pat Inflamm Allergy Drug Discov
2:24–46
Rigas DA, Osgood EE (1955) Purification and properties of the phytohemagglutinin of Phaseolus
vulgaris. J Biol Chem 212:607–615
Shapiro LE, Shear NH (1996) Mechanisms of drug reactions: the metabolic track. Semin Cutan
Med Surg 15:217–227
Shear NH, Spielberg SP (1988) Anticonvulsants hypersensitivity syndrome: in vitro assessment of
risk. J Clin Invest 82:1826–1832
Spielberg SP (1980) Acetaminophen toxicity in human lymphocytes in vitro. J Pharmacol Exp
Ther 213:395–398
Spielberg SP, Gordon GB, Blake DA et al (1981a) Anticonvulsant toxicity in vitro: possible role of
arene oxides. J Pharmacol Exp Ther 217:386–389
Spielberg SP, Gordon GB, Blake DA et al (1981b) Predisposition to phenytoin hepatotoxicity
assessed in vitro. N Engl J Med 305:722–727
Stevenson RD, Wolraich ML (1989) Stimulant medication therapy in the treatment of children
with attention deficit hyperactivity disorder. Pediatr Clin North Am 36:1183–1197
Stricker BC, Psaty BM (2004) Detection, verification, and quantification of adverse drug reactions.
Br Med J 329:44–47
Tennis P, Stern RS (1997) Risk of serious cutaneous disorders after initiation of use of phenytoin,
carbamazepine, or sodium valproate: a record linkage study. Neurology 49:542–546
Wu Y, Sanderson JP, Farrell J et al (2006) Activation of T cells by carbamazepine and carbamaz-
epine metabolites. J Allergy Clin Immunol 118:233–241
Zaccara G, Franciotta D, Perucca E (2007) Idiosyncratic adverse reactions to antiepileptic drugs.
Epilepsia 48:1223–1244
Zielinskin SL (2005) FDA attempting to overcome major roadblocks in monitoring drug safety.
J Natl Cancer Inst 97:872–873
Small Sample Approach, and Statistical
and Epidemiological Aspects
Martin Offringa and Hanneke van der Lee
Contents
1 Part 1: Design of Pharmacokinetic Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
1.1 Pharmacokinetics Trials, the Classical Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 182
1.2 Population Pharmacokinetics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 183
2 Part 2: Phase III Clinical Trials: Classic and Novel Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
2.1 When Is a Phase III Clinical Trial Necessary? . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
2.2 Classical Sample Size Calculations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 184
2.3 Inadequate Sample Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
2.4 Classical Strategies to Minimize Sample Sizes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 187
2.5 Group Sequential Design, Boundaries Design,
and Adaptive Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 191
3 Part 3: Conduct of Trials and Working with DMCs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
4 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 199
Abstract In this chapter, the design of pharmacokinetic studies and phase III trials
in children is discussed. Classical approaches and relatively novel approaches,
which may be more useful in the context of drug research in children, are discussed.
The burden of repeated blood sampling in pediatric pharmacokinetic studies may be
overcome by the population pharmacokinetics approach using nonlinear mixed
effect modeling as the statistical solution to sparse data. Indications and contrain-
dications for phase III trials are discussed: only when there is true “equipoise” in the
medical scientific community, it is ethical to conduct a randomized clinical trial.
The many reasons why a pediatric trial may fail are illustrated with examples.
Inadequate sample sizes lead to inconclusive results. Twelve classical strategies to
minimize sample sizes are discussed followed by an introduction to group
M. Offringa (*) • H. van der Lee

Department of Paediatric Clinical Epidemiology, Emma Children’s Hospital, Academic Medical
Centre, University of Amsterdam, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands
e-mail: m.offringa@amc.uva.nl

182 M. Offringa and H. van der Lee
sequential design, boundaries design, and adaptive design. The evidence that these
designs reduce sample sized between 35 and 70% is reviewed. The advantages and
disadvantages of the different approaches are highlighted to give the reader a broad
idea of the design types that can be considered. Finally, working with DMCs during
the conduct of trials is introduced. The evidence regarding DMC activities, interim
analysis results, and early termination of pediatric trials is presented. So far
reporting is incomplete and heterogeneous, and users of trial reports may be misled
by the results. A proposal for a checklist for the reporting of DMC issues, interim
analyses, and early stopping is presented.
Keywords Pharmacokinetics • Sample size • Power • Phase III trial • Pediatrics •

Child • Data Monitoring Committees • Interim analysis • Sequential design •
Triangular test
1 Part 1: Design of Pharmacokinetic Studies
1.1 Pharmacokinetics Trials, the Classical Approach
The goal of pharmacokinetic (PK) studies is to obtain generalizable information

about Absorption, Distribution, Metabolism, and Excretion (ADME) to make
rational dosing and administration decisions. For many drugs, PK information is
available from adults, but the question is whether this information can be
extrapolated to children. For many drugs, we know that this is not the case. Children
differ from adults with regard to the ADME characteristics in various ways, and,
moreover, within the wide age range from premature to adolescent there is no linear
development. Thus, PK studies need to be performed in various age groups. The
choice of these groups and the priority between age categories depend on clinical,
pathophysiological, and pharmacological considerations.
The classical approach of a PK study is a dose-escalation study. Participants are
randomized to receive either a prespecified dose or placebo; blood is drawn after,
e.g., 0.5, 1, 2, 4, 6, 8, 12, 16, and 24 h. Several dosages are specified in advance and
investigated simultaneously or sequentially. When dosages are investigated sequen-
tially, an interim analysis is performed after each dose has been tested in a
prespecified number of individuals. If there are no reasons to stop the study (either
because there is no relevant difference with the former dose or because of safety),
the next higher dose is investigated in the next group of participants. As an example,
the results are shown of a PK study of lisdexamfetamine dimesylate in children with
attention-deficit/hyperactivity disorder (ADHD) aged 6–12 (Boellner et al. 2010)
(Table 1).
The number of participants in a classical PK study is usually based on earlier
information about the variability of results. Typically between 10 and 20
participants are included for each dosage to be studied.
Small Sample Approach, and Statistical and Epidemiological Aspects 183
Table 1 PK study of lisdexamfetamine dimesylate in children with attention-deficit/hyperactivity

disorder (reprinted with permission from Boellner et al. 2010)
LDX dose (mg)
Pharmacokinetic parameter 30 (n ¼ 16a) 50 (n ¼ 17) 70 (n ¼ 17)
*
Cmax, ng/mL Mean (SD) , %CV 53.2 (9.62), 18.1 93.3 (18.2), 19.5 134 (26.1), 19.4
Tmax, h Mean (SD), %CV 3.41 (1.09), 31.9 3.58 (1.18), 33.0 3.46 (1.34), 38.6
t1/2, h Mean (SD), %CV 8.90 (1.33), 15.0 8.61 (1.04), 12.1 8.64 (1.32), 15.3
AUC01, ng/mL/h Mean (SD)*, 844.6 (116.7), 1,510.0 (241.6), 2,157.0 (383.3), 17.8
%CV 13.8 16.0
AUC0t, ng/mL/h Mean (SD)*, 745.3 (129.3), 1,448.0 (246.7), 2,088.0 (394.0), 18.9
%CV 17.4 17.0
a
Pharmacokinetic data were unavailable in one patient at the 30-mg dose; this patient was
excluded from the analysis
*
P < 0.001 (ANOVA)
In a sequential dose-escalation study, sometimes dose finding is approached by

“continual reassessment” methods, in which the next dosage is defined based on the
results of the earlier steps. According to the Efficacy Working Party of the
European Medicines Agency (EMA) Committee for Medicinal Products for
Human Use (CHMP): “The properties of such methods far outstrip those of
conventional ‘up and down’ dose finding designs. They tend to find the optimum
(however defined) dose quicker, they treat more patients at the optimum dose, and
they estimate the optimum dose more accurately” (CHMP 2006b).
1.2 Population Pharmacokinetics
In pediatric PK studies, the burden of repeated blood sampling is a problem. In the

ADHD example, blood samples were taken from an indwelling catheter to mini-
mize pain from multiple hand vein sticks. In younger children, blood sampling may
be an even greater challenge. In neonates or premature infants, not only the number
of samples, but also the amount of blood that can be withdrawn for each measure-
ment has to be minimized, thus making great demands on the analysis techniques to
measure drug levels.
In a population PK study, each individual contributes to the dataset with a small
number of (typically 2) samples. By using nonlinear mixed effect modeling, e.g.,
with the NONMEM program, PK parameters are estimated taking into account the
variability within and between individuals (De Cock et al. 2010).
Validation is necessary, first in existing datasets, or in a part of the original
dataset in which the PK model was built, and subsequently in prospective studies.
Proper validation is reported to have been performed only in a minority of PK
studies (De Cock et al. 2010).
For prospective studies, several software packages can help define the optimal
number of participants and sampling frame, e.g., WINPOPT and PopED. It should
be acknowledged that many factors have to be taken into account (Ogungbenro and
Aarons 2008).
2 Part 2: Phase III Clinical Trials: Classic and Novel Designs
2.1 When Is a Phase III Clinical Trial Necessary?
In the Christmas issue of the British Medical Journal of 2003, a paper was published
entitled “Parachute use to prevent death and major trauma related to gravitational
challenge: systematic review of randomised controlled trials” (Smith and Pell
2003). It is not surprising that the literature search preformed to detect any such
RCTs yielded no results. When the natural course of a disease is known, and case
reports show clearly and unambiguously that a particular intervention changes the
natural course in the preferred direction, it would be unethical to include patients in
a randomized clinical trial (Glasziou et al. 2007; Peto and Baigent 1998). Examples
of this principle are PGE1 infusion for ductus patency in newborns with obstructive
right heart malformation and indomethacin treatment of newborns with
life-threatening polyuric salt-losing tubulopathies (SLTs). The therapeutic advan-
tage of these treatments is beyond any doubt. Only when there is true “equipoise” in
the medical scientific community, it is ethical to conduct an RCT (Edwards et al.
1998). In the development of new drugs, RCTs usually cannot be avoided. How-
ever, it is not always necessary or ethical to perform these trials in children
(Sammons 2011).
2.2 Classical Sample Size Calculations
Imagine a pediatrician who wants to investigate whether a new drug leads to more
improvement in a specified outcome than the old drug. How many patients does he
or she need to include in the study? The consulted statistician will explain that the
required sample size is defined by the power of the study, the significance level,
whether a one- or two-sided test is required, the variance of the outcome in the study
population, and the expected or clinically relevant difference in the outcome
between the two intervention groups to be detected.
2.2.1 Sample Size Calculation and Power
Sample size calculations are necessary to minimize the risk of false-negative

results. Although often neglected, there is also a risk of a false-positive result in
hypothesis testing. When the threshold a for the level of statistical significance is set
at 0.05, this means that we accept a false-positive rate of 5%.
The null hypothesis H0 to be tested states that there is no difference in outcome
between the groups and the alternative hypothesis states that there is a difference. In
case of a two-sided test, which is usually applied, the difference can either mean
superiority or inferiority of the experimental intervention compared to the control
intervention.
A one-sided test is applied if inferiority of the experimental intervention is
considered very improbable (Knottnerus and Bouter 2001). The result of a one-
sided test can either be non-inferiority, i.e., not worse, possibly better than the
control intervention, or superiority, i.e., definitely better than the control interven-
tion. When a one-sided test is applied, the null hypothesis states that the effect of the
experimental intervention is either worse, in case of a non-inferiority trial, or worse
than or equal to the control intervention, in case of a superiority trial. If the data that
are obtained in the study are very unlikely under the null hypothesis, so unlikely
that the probability to obtain these or more extreme data is smaller than a, we reject
the null hypothesis. This leaves a probability of a for a false-positive result or type I
error.
If the alternative hypothesis is true, there is a risk, called b, of obtaining data that
are not unlikely under the null hypothesis, which leads to a false-negative result or
type II error. Usually, the risk of a type II error (false-negative result) is considered
to be less undesirable than a type I error. Therefore, b is usually set at 10 or 20%.
The power of a study is the probability of rejecting the null hypothesis if
the alternative hypothesis is true, i.e., 1 b. As an example, the general formula
for a continuous outcome measure to calculate the required sample size for a T-test
is as follows:
s2
N ¼ ðZa=2 þ Zð1bÞ Þ2 (1)
ðm1 m2 Þ2
s2 ¼ s21 þ s22 2rs1 s2 (2)
In which N is the number of subjects per group, Za/2 is the value of the standard
Normal distribution corresponding with the chosen value of a (two-sided), Z(1b) is
its equivalent for the chosen value of b, s2 is the variance of the outcome variable in
Table 2 Theoretical probabilities of correct and false conclusions of hypothesis testing

Investigator’s conclusion (Unknown) reality
H0 true H0 not true
H0 not rejected 1a b
type II error
H0 rejected a 1b
type I error power
level of significance
H0 ¼ Null hypothesis
the study population, which is the sum of the variances in the two groups minus two
times the product of the standard deviations in the two groups multiplied by the
correlation between the observations (r ¼ 0: unpaired t-test, r > 0 paired t-test),
and m1 and m2 are the estimated means of the outcome variable in the two groups to
be compared.
From this formula, it becomes clear that the required sample size increases if we
choose a smaller risk of type I (a) or type II errors (b), if the variability s2 is larger,
or if the difference that we want to be able to detect (m1 m2) is smaller.
These days regulatory authorities and many journal editors request that the
results of a study are expressed as point estimates and 95% Confidence Intervals
(CIs). The advantage of this presentation, estimation instead of hypothesis testing,
is that the size of the effect can be appreciated as well as its statistical significance.
Thus, a small effect with a narrow CI may be statistically significant, i.e., the neutral
value lies outside the CI, but because of its small size the effect may be considered
to be clinically irrelevant, whereas a large effect that is not statistically significant –
i.e., p > 0.05; neutral value inside CI – may be considered to be important for
clinical practice. However, if the CI is wide, more information is needed to get a
precise estimate. It is quite possible that the effect found in one small study turns
out to be negligible when the study is replicated in a larger sample.
2.2.2 Practical and Ethical Issues
When designing a clinical trial, the probability of finding an effect if there is one in
reality, i.e., a true-positive result, should be maximized, irrespective of whether the
result will be expressed as estimation or as a hypothesis test. As we have seen, this
can be achieved by maximizing the number of subjects included in the study.
However, there are practical and ethical restraints to the inclusion of large numbers
of subjects, especially in the pediatric population. Usually, the number of children
eligible for the study is limited because many conditions are uncommon.
Furthermore, the financial and time resources are always limited. Apart from
that, clinicians have an ethical obligation to give the best treatment to their patients.
As long as there is equipoise, i.e., the medical scientific community is uncertain
which treatment is best, it is justified to include patients in a clinical trial. However,
suppose there were no practical limitations to including patients in a trial, and a
researcher would continue including patients, at a certain moment the results could
be expressed in a very narrow CI. At what moment would equipoise be abandoned?
That would be the moment to stop including patients in the trial and to start treating
consecutive patients with the optimal intervention mode. Therefore, for each trial it
has to be stated in advance when to stop including patients. Usually, this is done by
calculating the number of patients needed to get 80 or 90% certainty that if there is
an effect of a predefined size, it will be found statistically significant at a ¼ 0.05.
However, this calculation often leads to required sample sizes that are very hard, or
impossible to attain.
2.3 Inadequate Sample Size
Inadequate sample sizes lead to inconclusive results. As an example, from December

1997 to March 2001 data were collected for a multicenter randomized placebo-
controlled trial in the Netherlands to evaluate the efficacy of intravenous dexametha-
sone in young patients mechanically ventilated for respiratory syncytial virus lower
respiratory tract infection (van Woensel et al. 2003). Randomization was stratified by
center. The number of patients to be included was calculated based on the notion that a
between-group reduction in duration of mechanical ventilation of 1.5 days was
clinically relevant.
The authors reported a mean difference between the placebo group and the
dexamethasone group of 1.6 days; 95% CI ¼ 0.8 to þ3.8 days. Thus, the point
estimate showed a clinically relevant difference, but the 95% CI was not narrow
enough to reach statistical significance. This 95% CI indicates that dexamethasone
may reduce the duration of mechanical ventilation with almost 4 days or it may
extend its duration with almost 1 day. It means that, although the difference is not
statistically significant, the possibility of a clinically relevant beneficial effect of
dexamethasone has not been excluded.
This result could be described as “no evidence of effect” (Tarnow-Mordi and
Healy 1999). Clinicians need to make decisions about the administration of
treatments, in this case dexamethasone. Inconclusive evidence is better than no
evidence at all, but not really helpful in clinical decision-making.
What was the reason that no definitive, statistically significant result was found
in this trial? As it turned out, the sample size estimation was based on too optimistic
assumptions for the variability of the outcome measure; a flaw that is often
encountered (van der Lee et al. 2009; Vickers 2003).
2.4 Classical Strategies to Minimize Sample Sizes
The problem of limited availability of subjects to be included in a trial has led to

different strategies used by researchers to improve power. As was stated in the
EMA guideline on clinical trials in small populations (CHMP 2006a), “No methods
exist that are relevant to small studies that are not also applicable to large studies.
However, it may be that in conditions with small and very small populations, less
conventional and/or less commonly seen methodological approaches may be
acceptable if they help to improve the interpretability of the study results.”
We describe 12 possible approaches, i.e., (1) use of one-sided instead of two-
sided hypothesis testing, (2) inflation of the minimal clinically relevant difference,
(3) composite or (4) surrogate outcomes, (5) improved reproducibility of outcome
measurements, (6) repeated measurements, (7) the crossover design, (8) matching
or stratification, (9) analysis of covariance instead of simple comparison of
outcomes in two groups, (10) response-adaptive design, (11) conducting an
underpowered trial for a later meta-analysis, and (12) the prospective meta-analysis
approach. Table 3 gives an overview of these approaches, their drawbacks, and
their applicability in pediatric drug development trials.
Ad (1) One-sided instead of two-sided testing has been suggested for ethical and
efficiency reasons when inferiority of the experimental intervention is
considered very improbable (Knottnerus and Bouter 2001). However,
other authors are convinced that each randomized trial should also be
able to detect harm in terms of a worse outcome due to the experimental
intervention (Moye and Tita 2002). Usually, one-sided testing is limited to
the non-inferiority design.
Ad (2) The assumptions to be made in advance in the design phase of the study are
often arbitrary. Sometimes negotiations take place between the researcher
and the statistician. “If we want to detect a 10% difference, we need 132
patients but if we expect the difference to be 15%, we need 52 patients.”
Since there are no criteria to be used in defining the minimal clinically
relevant difference, this is often used as a “closing entry.” The number of
patients that can be recruited is usually the limiting factor, a and b are
more or less predetermined, and the variance in the study population
cannot be altered. This leaves the minimal clinically relevant difference
as the only input in the power formula that can be adjusted. This procedure
has been referred to as a “sample size samba” (Schulz and Grimes 2005).
Ad (3) In the field of AIDS research, the “simple” outcome mortality became less
frequent due to advances in treatment. The use of mortality as an outcome
variable would have led to an increase in the required sample size.
Therefore, composite outcomes were formulated, consisting of a number
of possible adverse events, e.g., first symptoms of disease progression
expressed as neurological symptoms or growth retardation (McKinney
et al. 1998).
Ad (4) Another way of increasing power is to use surrogate outcomes, which
allow a smaller size of the study population, for instance, glomerular
filtration rate instead of patient or graft survival in renal transplant trials
(Filler et al. 2003). An important prerequisite for a surrogate outcome is
that its predictive validity or association with the “true clinical outcome”
should be established (CHMP 2006a).
Ad (5) If the outcome measure is a continuous variable, it may be possible to
improve its reproducibility and in this way reduce the Standard Deviation.
Improving the reproducibility typically starts with a clinimetric study,
sometimes called a Generalizability study, in which the influence of
several possible sources of variability, called “facets,” is quantified. Sub-
sequently, approaches are proposed and investigated to improve the
reproducibility of the measurement. Depending on the type of measure-
ment, these approaches may consist of better standardization of the mea-
surement process or of the use of a mean value of repeated measurements
instead of one single measurement value. The effect of such a mean value,
Table 3 Classical approaches to minimize sample size

Principle Application (related Drawbacks Recommendation
to approach # in text) for pediatric drug
trials
Enhancing statistical power
Significance Increased risk of type I error
level "
One-sided instead of Less convincing, no conclusion +/
two-sided test (1) about possible harm
Minimal “Sample size Risk of missing a truly relevant
clinically samba” (2) effect
important
difference "
Variance # In most instances, this cannot be
influenced
Composite Conclusion may be based on less +
outcomes (3) relevant components of the
composite outcome
Surrogate Validity issue: association with truly +/
outcomes (4) relevant outcomes is often
insufficient or unknown
Improve Practical and logistical constraints +
reproducibility
(5)
Repeated Practical, logistical, financial, and +
measurements ethical constraints
(6)
Crossover design (7) Only possible in chronic conditions
for treatments with no carry-over
effect; very seldom in children
Restriction, Selection of study participants +/
matching, jeopardizes recruitment;
andstratification limitation of external validity
(8)
Analysis of Only applicable when outcome is +
covariance (9) continuous and can be assessed
before randomization and after
the intervention
Minimizing sample size while preserving power
Response-adaptive Cumbersome; only for short term +/
design (10) outcomes; modest effects on
sample size
Beyond single trials
Meta-analysis of Often heterogeneity between trials, a
several small e.g., variability in inclusion
trials (11) criteria, dosages, comparisons,
and outcome measures
Prospective meta- Organizational challenge; ++
analysis (12) discouraged by publication
policies
a
Retrospective meta-analysis is considered very relevant for clinical guideline development, but
not for drug development
and the optimal number of repeated measurements, can be investigated in

a so-called Decision study, which consists of simulations based on the
information from the G-study (Streiner and Norman 2008).
Ad (6) The use of repeated measurements to increase statistical power often
has important practical limitations. Nevertheless, in some cases it may
be possible to use repeated outcome measures. The number of subjects
required is then obtained by multiplying formula (1) with
f1 þ ðT 1Þrg=T, in which T is the number of measurements and r is
the correlation between subsequent measurements in the same subject.
For instance, if the number of subjects needed is 60, this can be reduced to
40 by using three measurements instead of one, assuming the correlation
between measurements to be 0.5 (Twisk 2003).
Ad (7) In a crossover design, the sample size is reduced because all subjects serve
as their own controls and the reduction in sample size is linearly related to
the observed correlation (r) between the measurements under the two
treatments (see equation 2) (von Goedecke et al. 2005). The correlation
between the measurements is usually estimated to be 0.5 in a crossover
trial. Thus, a parallel trial, for which 502 children would be required
(a ¼ 0.05, b ¼ 0.20, effect size is 0.25), could be replaced by a crossover
trial including 126 children. The most important requirement for a cross-
over design is that there is no carry-over effect, i.e., that the treatment
given in the first phase has no influence at all during the second phase of
the study (Woods et al. 1989). This requirement is often not convincingly
met. Especially in pediatric research this is hard to prove, when the
outcome may be influenced by developmental factors. A particular type
of crossover design is the N-of-1 trial series, in which several – usually
more than 2 – treatment periods of the drugs under investigation are
randomized in individual patients. The advantage of this type of trial is
that each participant will finally find out which drug is best for him or her.
Disadvantages are, apart from the requirements that need to be met for all
crossover trials, the limited external validity or generalizability to other
patients.
Ad (8) Restriction by using severe inclusion criteria leads to less variability
between trial subjects, but limits the external validity of a trial and may
hamper recruitment, which is often a limiting factor in the execution of a
pediatric trial. Restriction, matching, or stratification makes the analysis
more efficient. However, the influence of the matching factors cannot be
investigated anymore.
Ad (9) Analysis of covariance including the baseline score as a determinant in the
analysis adds information to the analysis and improves the statistical
power, as was shown by Vickers and Altman. This approach is comparable
to the repeated measurements approach (Vickers and Altman 2001).
Ad (10) Response-adaptive design is a way of treatment allocation aimed at
maximizing the power and minimizing the number of patients allocated
to the “inferior” treatment while preserving randomization. One of the
requirements for this type of design is that outcomes should become

available early in the trial. The effect on total sample size is modest
(Rosenberger and Huc 2004).
Ad (11) Some scientists state that conducting an underpowered trial is unethical
(Freiman et al. 1978). However, given the small numbers of specific
diagnoses seen in most pediatric clinics, the only way to obtain a sufficient
sample size is by conducting a (international) multicenter study, which is
hampered by practical and logistic problems. Therefore, it may be more
realistic to perform a small, underpowered trial, the results of which are
presented in such a way that they can be incorporated in a meta-analysis
(Sackett and Cook 1993).
Ad (12) A recent development is a prospective meta-analysis using individual
patient data. This is a type of design which combines some aspects of a
multicenter study with a meta-analytic approach (Simes 1995).
2.5 Group Sequential Design, Boundaries Design,

and Adaptive Design
The principles of randomized clinical trials were originally derived from agricultural
research, in which the statistical methods of analysis of variance and regression
analysis were developed (Whitehead 1997). An essential difference between agricul-
tural and clinical trials is the time period during which data are gathered. In an
agricultural field trial, all crops are harvested simultaneously at the end of the growth
season, whereas in clinical trials it usually takes weeks or months, sometimes even
years before all subjects are included, and consequently the gathering of the outcome
data is extended over a similarly long time period. Thus, it is possible that before the
end of the inclusion phase of a clinical trial enough information has already been
assembled, though usually not analyzed, to decide which intervention is superior.
Because subjects will be included and randomized until the sample size that was
determined in advance has been reached, this may lead to inefficiency, that is,
inappropriate inclusion of subjects, unnecessarily prolonging the trial duration, and,
more importantly, to allocation of trial subjects to the “inferior” intervention at a
time when the evidence of its inferiority might be available. Some authors have
referred to such practices as substandard or unethical (van der Lee et al. 2010;
Whitehead 1997). Sequential designs were developed to overcome these problems.
Various sequential procedures exist, and they can be (roughly) divided into two
types, namely those derived from the repeated significance test approach, also
called group sequential designs, and those derived from the boundaries approach.
Because there is no uniform terminology, we make a distinction between “design”
and “analysis” (Sebille and Bellissant 2003). Thus, within the boundaries design a
distinction can be made between “continuous sequential analysis” and “group
sequential analysis.” Recently, a modification of the group sequential design has
been proposed, called the adaptive design. We will discuss the group sequential
design, the boundaries design, and adaptive design in more detail below.
2.5.1 Group Sequential Design, Repeated Significance Testing
In this approach, a series of conventional statistical analyses, so-called interim

analyses, are carried out at various predetermined time points on the accumulating
data. The basis for this methodology was laid by Armitage in the 1970s (Armitage
1958, 1975). To ensure an overall type I error probability (a), the significant
thresholds at the various time points are adjusted to allow for the repetition (a*).
Various methods for a-adjustment have been proposed, either with the same a* for
all analyses, Pocock’s method (Pocock 1977), which is seldom used, or with
different a* at each analysis, for example, O’Brien and Fleming (1979), and
Haybittle and Peto (Haybittle 1971). As an example, when two analyses are
planned, i.e., one interim and one final analysis, the method of O’Brien and Fleming
prescribes a* of 0.0054 and 0.0492 for the interim and the final analysis, respec-
tively. In the same situation, a* would be 0.0100 and 0.0500 for the interim and the
final analysis, respectively, for the Haybittle–Peto method. In contrast to the earlier
methods of Pocock, O’Brien and Fleming, and Haybittle–Peto, the so-called a-
spending function developed by Lan and De Mets (Lan and DeMets 1983) that
characterizes the rate at which the a is spent and thus determines the a* at each
interim analysis only depends on the number of past and current interim analyses
and not on the number of future interim analyses. This approach enhances the
flexibility of the design, because the number of (interim) analyses does not have to
be predetermined. Further modifications included the possibility of stopping early
when there is no relevant difference between the intervention groups (stopping for
futility) (Emerson and Fleming 1989; Pampallona and Tsiatis 1994).
An example of a useful interim analysis, when the original effect size estimation
appeared too conservative in retrospect, is a randomized clinical trial to investigate
the difference in incidence of injection pain during intravenous induction of
anesthesia in children between a new formulation (Etomidate–®Lipuro) and the
existing standard of propofol with added lidocaine (Nyman et al. 2006).
The required sample size, calculated based on an expected proportion of 25% in
the propofol–lidocaine group and 5% in the Etomidate–®Lipuro group, a of 0.05,
and power of 90%, was reported to be 110. On request of the Ethics Committee, an
interim analysis was planned after the inclusion of 80 patients, with a nominal value
a* ¼ 0.02. The rationale for the interim analysis was to prevent unnecessary
injection pain in children if there was a difference in pain incidence between the
two groups. The underlying considerations for the timing and a* of the interim
analysis were not reported. The study was ended when this interim analysis showed
a significantly lower incidence of injection pain in the Etomidate–®Lipuro group
(5%; 95% CI ¼ 0.61–16.9%) than in the propofol–lidocaine group (47.5%; 95%
CI ¼ 31.5–63.9%) (P ¼ 0.0007) (Nyman et al. 2006).
2.5.2 Boundaries Design
This approach relies on a graphical rule, where a V statistic, representing the

amount of information gathered in the course of a trial, is plotted on the X-axis,
and a Z statistic, representing the effect size, is plotted on the Y-axis. Prior to the
start of the experiment, the boundaries are calculated based on the alternative
hypothesis and the desired levels of the type I and II errors (a and b, respectively).
Examples of boundaries are shown in Fig. 1.
Tests of this type are descendants of the sequential probability ratio test (SPRT) of
Wald (Wald 1947; Whitehead 1997). Initially, these methods could only be used to
compare a single proportion or mean to a hypothetical value, or for the comparison of
two proportions (paired observations). These restrictions hampered a successful
application of these types of tests. After modifications by Whitehead (Whitehead
and Jones 1979; Whitehead and Stratton 1983), comparison of two independent
groups with respect to continuous, binomial (e.g., alive/dead), or censored outcomes
(survival data) was possible, thus increasing the applicability of the methods. In an
SPRT, the boundaries are parallel (Fig. 1a), giving an infinite “continuation region.”
Therefore, it is theoretically possible that a trial requires an almost infinite value of V
(and thus n), which renders this test impracticable for clinical trials.
60 60
a b
40 40
Z 20 Z 20
0 0
-20 -20
0 100 200 300 0 100 200 300
V V
60 60
c d
40
40
20
Z 20 Z 0
-20
0
-40
-20 -60
0 100 200 300 0 100 200 300
V
Fig. 1 Boundaries design in four hypothetical cases – see text for details (reprinted with
permission from van der Lee et al. 2008)
At each analysis, which can be done after each patient (continuous sequential
analysis) or after a fixed or variable number of patients (group sequential analysis),
the two statistics Z and V are calculated based on the data accumulated thus far, and
plotted, creating a so-called sample path. This is illustrated in Fig. 2.
Inclusion and randomization of subjects are continued as long as the sample path
remains between the boundaries (continuation region). A conclusion is reached
when a boundary is crossed. In case of a one-sided test, that is, investigating only
whether the experimental treatment leads to a better outcome than the control
treatment, a single pair of boundaries is plotted (Fig. 1a–c). Crossing of the upper
boundary leads to rejection of the null hypothesis; crossing of the lower boundary
leads to non-rejection of the null hypothesis.
Two pairs of boundaries are plotted symmetrically around the horizontal axis in
case of a two-sided test, in which both possibilities of better and worse outcomes of
the experimental compared to the control treatment are investigated (Fig. 1d).
Crossing of the upper or lower boundary leads to the conclusion that the experi-
mental treatment is superior or inferior, respectively; crossing of the boundaries
between both pairs of boundaries leads to non-rejection of the null hypothesis.
Alternatives that are useful in clinical trials are the truncated SPRT (Fig. 1b) and
the triangular test (TT) (Fig. 1c) (Anderson 1960; Whitehead 1997). In the
truncated SPRT, a maximum value (L) of V is determined after which the trial
stops, irrespective of the result. This truncation point L is chosen more or less
arbitrarily, but it has to be beyond the amount of information VFIXED required for
the equivalent fixed sample design to correct for multiple hypothesis testing. The
space between the parallel boundaries is influenced by the choice of L. In other
words, the choice of L has consequences for the sample size. For a given a, b, and
effect size, the boundaries are closer to each other with increasing L. In case of the
TT (Fig. 1c, d), the boundaries are convergent, resulting in a finite “continuation
region.” Therefore, the optimal properties of the SPRT and TT differ: the average
sample size reduction is larger with the SPRT when the actual effect size is (much)
larger than expected and smaller when the actual effect size is smaller than
expected (Fig. 1a vs. c) (Sebille and Bellissant 2000). When the actual and expected
effect sizes are similar, the expected sample size reductions are about equal.
Obviously, it is impossible to predict whether the actual effect size will be smaller
or larger than the expected effect size. In practice, in most trials, the actual effect
size turns out to be smaller than expected. In those cases, the TT is more efficient
(Sebille and Bellissant 2000). In contrast to the classical fixed sample size design,
the eventual amount of information, that is, number of patients, needed to complete
a trial is unknown at the start of a sequential trial. The choice of design usually
depends on the statistician’s expertise and the availability of the software.
Although correction for multiple testing results in a larger maximal possible
sample size (the amount of information which is represented by the apex of the
triangle in Fig. 1c, d), the average sample size needed to complete a trial using a
sequential method in simulations was always smaller than that of the corresponding
fixed design, irrespective of the effect size or power (Sebille and Bellissant 2000).
The 90th percentiles of the sample size distributions of the sequential designs were
in the same order of magnitude as the corresponding fixed designs, when the actual
effect was close to the expected effect, but larger when the actual effect was smaller
than expected, especially for the SPRT. In principle, Z and V can be calculated after
each individual patient, but generally Z and V are calculated after the data of a
number of patients have become available, that is, group sequential analysis.
Given the possibility that intermediate points, if plotted, could have lain outside
the triangular region during long gaps between inspections, and thus opportunities
for stopping might have been missed, an adjustment of the stopping boundaries is
made, resulting in a so-called Christmas tree shape (Fig. 2). After a boundary has
been crossed, an adjusted point estimate and CI of the effect can be calculated with
the computer program PEST or EaSt (2004; Cytel Software Corporation 1992). Due
to the sequential nature of the analysis, the CIs are wider than those obtained with
conventional fixed sample size methods of analysis.
In summary, the advantage of a sequential design is that the inclusion and
randomization can be stopped when enough information is available to draw a
definite conclusion, of either futility or efficacy, based on statistical significance.
For a sequential trial to be feasible, the time from randomization to outcome should
be limited relative to the recruitment rate. On average, the number of subjects
needed is smaller than in a classical fixed sample size design. However, in a
particular trial it may be larger than that. Drawbacks are that the eventual sample
size is not exactly known at the start, which hampers logistic and financial planning,
and that the 95% Confidence Intervals around the point estimate of the effect size
are somewhat wider than when there is only one analysis at the end of the trial.
Fig. 2 One-sided superiority triangular test and sample path of a trial (reprinted with permission
from van der Lee et al. 2008)
Table 4 Relative benefits and drawbacks of fixed sample size and triangular test
Fixed sample size Triangular test
Risk of biased end Small if conducted according to Data analysis should be
result well-known standards; if no independent from trial
interim analyses have been performance and masked;
planned, analysis can be done important that confidentiality of
by investigators after all trial results is ensured until the end
data have been assembled of the trial
Feasibility in a Logistics are known in advance; Number of patients to be included
multicenter trial planning for a specific number unknown at study onset;
of trial patients; outcome planning may be hampered by
information may be assembled uncertainties; block-
per center and sent to randomization necessary to
coordinating center later avoid discrepancies in numbers
per arm; outcome information
has to be sent to coordinating
center immediately when it
occurs or is measured
Familiarity, Very well known, generally Less familiar design; despite unjust
acceptance by accepted as the most valid suspicion for increased risk of
funders, editors, design to answer questions of type I errors, final analysis is
peers, and readers effects of interventions valid, maintaining type I error
and power
In Table 4, the relative benefits and drawbacks of the fixed sample size and
triangular test are presented (van der Lee et al. 2009).
Bellissant et al. described a TT to assess the efficacy of metoclopramide on
gastroesophageal reflux in infants (Bellissant et al. 1997). The trial was designed to
detect a mean benefit on a continuous outcome scale of 0.5 with an expected
standard deviation of 0.5 with 95% power and a one-sided a of 0.05. In a fixed
design, 23 patients per treatment arm would have to be included. The authors
anticipated that recruitment would be difficult and wanted to stop the study as
soon as sufficient information was collected and decided, therefore, to use the TT.
After 3 years and 9 months and inclusion of 39 children, the trial ended in futility,
because the lower boundary was crossed (Fig. 2). The observed benefit of
metoclopramide over placebo was approximately 0.2 instead of 0.5.
2.5.3 Adaptive or Flexible Design
Adaptive designs share a number of features with sequential designs, in which the
null hypothesis is tested at a sequence of interim analyses (Wassmer 2000).
However, in contrast, the design of an adaptive trial can be changed based on full
knowledge gained from the interim analyses. When modifications are made, a new
phase of trial starts, and data accumulated in (an) earlier phase(s) are no longer
combined with data from the new phase. All phases are analyzed separately, and the
P-values of the different phases are then combined using a predefined rule.
Examples of combination rules are the product criterion of Fisher (Bauer and
Kohne 1994) and the inverse normal method by Lehmacher (Lehmacher and
Wassmer 1999). The emphasis in these designs is more on flexibility of the design
than on minimization of the average sample size.
Different adaptations are possible including reassessment of sample size (see critical
reflection by Jennison and Turnbull 2003), selection of treatments (e.g., Hommel 2001;
Kelly et al. 2005), adaptation of end points (e.g., Bauer and Kieser 1999; Kieser
et al. 1999), or inserting or deleting interim analyses. See for a more extensive
description of this design the tutorial by Bretz et al. (2009). However, many features,
for example, definition of stopping rules (van Houwelingen 1999) or interpretation
of the results when primary end points have been changed, for instance, are still
subject for debate (CHMP 2006b).
The term “adaptive design” is a comprehensive term comprising many possible
design adaptations (CHMP 2006b). It should not be confused with the more specific
term “response-adaptive design,” discussed in section “Inadequate Sample Size”,
where the allocation ratio can be adapted based on preliminary results from the trial
(Coad and Ivanova 2005). To our knowledge, no pediatric trials with an adaptive
design have been published so far. Because it maximizes the efficiency of data
gathering from individual patients, this approach deserves more attention (Hirtz
et al. 2006).
2.5.4 Implications of Sequential and Adaptive Designs
In a systematic review of pediatric trials using a sequential design 24 sequential

trials, published between 1963 and 2005, were found (van der Lee et al. 2010). In
nine studies, the information about the assumptions was sufficient to calculate a
fixed sample size.
The median reduction in included sample size in these trials compared with the
fixed sample size calculation was 52 subjects (range: 22 to 229), a reduction of
35% (range: 42 to 90%) of the fixed sample size. The median sample size
reduction when considering the number of subjects included in the analysis until
crossing of the boundaries was 77% (range: 15–90%). In this review, the number of
trials stopped early for benefit (4) equaled the number of trials stopping early
because there was enough information not to reject the null hypothesis. In another
recent systematic review, the practice of stopping early for benefit was found to lead
to inflated effect sizes (Bassler et al. 2010). However, this review did not include
information on trials which were stopped early for futility.
Table 5 Proposed minimal set of parameters to be reported about DMC activities, interim
analysis and early stoppinga, b
Data Monitoring Committees and interim analysisb
Terminology
Use of the standard nomenclature “Data Monitoring Committee”
Composition of the DMC
Members’ name, affiliation, and training
Independence status from research team and sponsor
Tasks of the DMC
Whether the DMC reviewed and accepted the protocol before the start of the trial
Main roles (e.g., monitoring of safety and/or efficacy), and explicit definition of which outcomes
were analyzedc
Any additional roles (e.g., monitoring recruitment and quality assurance)
To which outcome(s) was the DMC blinded or unblinded
Interim analysis and statistical monitoring methods
Whether the protocol included a predefined statistical monitoring plan
Number of planned interim analyses
Timing of planned interim analyses and parameter defining timing (i.e., participants or person-
time recruitment, number of end points, and ad hoc time interval)
Type of analysis planned (i.e., efficacy, harm, futility, and/or sample size adjustment), specific
statistical methods used (with references and uniform terminology), description of boundaries
(i.e., their symmetry, p-value/confidence interval, and adjustment, if applicable), and outcome
(s) to which they were applied (i.e., primary/secondary, any subgroup analysis)
Any formal predefined stopping rules, to which outcome(s) did they apply, and whether they
included statistical boundaries and/or other considerations
Whether the statistical monitoring plan was completed as planned; if not, which changes were
performed, and their rationale
Adjustment for multiple analysis in final results (i.e., reported p-values and/or confidence
intervals)
Recommendations to the sponsor/steering committee
DMC recommendation regarding continuation or termination of the trial (with or without
adjustments in protocol)
Rationale (i.e., statistical boundaries and/or other considerations)
Whether the sponsor followed the DMC’s recommendations
Early terminated trials
Motive(s) for termination (e.g., efficacy, harm, futility, and recruitment)
All previously stated items, particularly rationale for early termination (including predefined
statistical monitoring plan, type of analysis, predefined stopping rules, and DMC
recommendation), and adjustment for multiple analysis and early termination in final results
Timing of early termination, i.e., which of the interim analyses led to trial termination, and on
which parameter the timing of this interim analysis was based (e.g., number of participants
enrolled and predefined number of end points)
Planned and final sample size
Total number of events after which the trial was terminated, including definition of these events
Discussion of implications of early termination (i.e., concerning type I ands II errors)
Report early termination in the abstract of the paper
a
These recommendations are for main reports; further details could be available using other modes
of publication (e.g., online appendices, trial design/protocol papers, and web-based repositories),
to which the report should refer to; planned items of this minimal set of parameters should be
included in prospective trial registries
b
Based on the book by Ellenberg et al. and the report of the DAMOCLES group (Ellenberg et al.
2002; Grant et al. 2005)
c
Particularly regarding safety – whether it included adverse events and/or main efficacy outcomes
3 Part 3: Conduct of Trials and Working with DMCs
In a systematic review of 648 pediatric trials published in eight high impact

journals, Fernandes et al. concluded that the reporting of DMC activities, interim
analysis results, and early termination of pediatric trials is incomplete and hetero-
geneous (Fernandes et al. 2009). Most of the included trials were, however,
designed and conducted before the DAMOCLES standards for DMC use were
published in 2005 (Grant et al. 2005). Fernandes et al. proposed a checklist for
the reporting of DMC issues, interim analyses, and early stopping, which is shown
in Table 5.
4 Conclusion
The goal of trialists in pediatric drug development is to design and conduct trials
that are valid, efficient, and safe. Various techniques are available to enhance the
efficiency of trials, without compromising their validity and safety. Few of these
techniques have been used on a large scale in pediatric drug development. We
suggest that experience and knowledge are shared on (internet) forums, such as
StaR Child Health (http://www.starchildhealth.org), to improve the standards of
pediatric trials and make sure that all children participating in drug trials benefit
from these standards (Klassen et al. 2009).
References
(2004) PEST 4.4 operating manual. The University of Reading, Reading

Anderson TW (1960) A modification of the sequential probability ratio test to reduce the sample
size. Ann Math Stat 31:165–197
Armitage P (1958) Sequential methods in clinical trials. Am J Public Health 48:1395–1402
Armitage P (1975) Sequential medical trials. Blackwell, Oxford
Bassler D, Briel M, Montori VM, Lane M, Glasziou P, Zhou Q, Heels-Ansdell D, Walter SD,
Guyatt GH, Flynn DN, Elamin MB, Murad MH, Abu Elnour NO, Lampropulos JF, Sood A,
Mullan RJ, Erwin PJ, Bankhead CR, Perera R, Ruiz CC, You JJ, Mulla SM, Kaur J, Nerenberg
KA, Schunemann H, Cook DJ, Lutz K, Ribic CM, Vale N, Malaga G, Akl EA, Ferreira-
Gonzalez I, Alonso-Coello P, Urrutia G, Kunz R, Bucher HC, Nordmann AJ, Raatz H, da Silva
SA, Tuche F, Strahm B, Djulbegovic B, Adhikari NK, Mills EJ, Gwadry-Sridhar F, Kirpalani
H, Soares HP, Karanicolas PJ, Burns KE, Vandvik PO, Coto-Yglesias F, Chrispim PP, Ramsay
T (2010) Stopping randomized trials early for benefit and estimation of treatment effects:
systematic review and meta-regression analysis. JAMA 303:1180–1187
Bauer P, Kieser M (1999) Combining different phases in the development of medical treatments
within a single trial. Stat Med 18:1833–1848
Bauer P, Kohne K (1994) Evaluation of experiments with adaptive interim analyses. Biometrics
50:1029–1041
Bellissant E, Duhamel JF, Guillot M, Pariente-Khayat A, Olive G, Pons G (1997) The triangular
test to assess the efficacy of metoclopramide in gastroesophageal reflux. Clin Pharmacol Ther
61:377–384
Boellner SW, Stark JG, Krishnan S, Zhang Y (2010) Pharmacokinetics of lisdexamfetamine
dimesylate and its active metabolite, d-amphetamine, with increasing oral doses of lisdexam-
fetamine dimesylate in children with attention-deficit/hyperactivity disorder: a single-dose,
randomized, open-label, crossover study. Clin Ther 32:252–264
Bretz F, Koenig F, Brannath W, Glimm E, Posch M (2009) Adaptive designs for confirmatory
clinical trials. Stat Med 28:1181–1217
CHMP (2006a) Guideline on clinical trials in small populations. EMA, London
CHMP (2006b) Reflection paper on methodological issues in confirmatory clinical trials with
flexible design and analysis plan. EMA, London
Coad DS, Ivanova A (2005) The use of the triangular test with response-adaptive treatment
allocation. Stat Med 24:1483–1493
Cytel Software Corporation (1992) EaSt: a software package for the design and interim monitoring
of group sequential clinical trials. Cytel Software Corporation, Cambridge, MA
De Cock RF, Piana C, Krekels EH, Danhof M, Allegaert K, Knibbe CA (2011) The role of
population PK-PD modelling in paediatric clinical research. Eur J Clin Pharmacol. 67 Suppl
1:5–16
Edwards SJ, Lilford RJ, Braunholtz DA, Jackson JC, Hewison J, Thornton J (1998) Ethical
issues in the design and conduct of randomised controlled trials. Health Technol Assess
2:1–132
Ellenberg SS, Fleming TR, DeMets DL (2002) Data Monitoring Committees in Clinical Trials.
Chichester, John Wiley Sons, Ltd
Emerson SS, Fleming TR (1989) Symmetric group sequential test designs. Biometrics 45:
905–923
Fernandes RM, van der Lee JH, Offringa M (2009) A systematic review of the reporting of Data
Monitoring Committees’ roles, interim analysis and early termination in pediatric clinical
trials. BMC Pediatr 9:77
Filler G, Browne R, Seikaly MG (2003) Glomerular filtration rate as a putative ‘surrogate end-
point’ for renal transplant clinical trials in children. Pediatr Transplant 7:18–24
Freiman JA, Chalmers TC, Smith H Jr, Kuebler RR (1978) The importance of beta, the type II
error and sample size in the design and interpretation of the randomized control trial. Survey of
71 “negative” trials. N Engl J Med 299:690–694
Glasziou P, Chalmers I, Rawlins M, McCulloch P (2007) When are randomised trials unneces-
sary? Picking signal from noise. BMJ 334:349–351
Grant AM, Altman DG, Babiker AB, Campbell MK, Clemens FJ, Darbyshire JH, Elbourne DR,
McLeer SK, Parmar MK, Pocock SJ, Spiegelhalter DJ, Sydes MR, Walker AE, Wallace SA
(2005) Issues in data monitoring and interim analysis of trials. Health Technol Assess
9:1–238
Haybittle JL (1971) Repeated assessment of results in clinical trials of cancer treatment. Br J
Radiol 44:793–797
Hirtz DG, Gilbert PR, Terrill CM, Buckman SY (2006) Clinical trials in children – how are they
implemented? Pediatr Neurol 34:436–438
Hommel G (2001) Adaptive modifications of hypotheses after an interim analysis. Biometrical
J 43:581–589
Jennison C, Turnbull BW (2003) Mid-course sample size modification in clinical trials based on
the observed treatment effect. Stat Med 22:971–993
Kelly PJ, Stallard N, Todd S (2005) An adaptive group sequential design for phase II/III clinical
trials that select a single treatment from several. J Biopharm Stat 15:641–658
Kieser M, Bauer P, Lehmacher W (1999) Inference on multiple endpoints in clinical trials with
adaptive interim analyses. Biometrical J 41:261–277
Klassen TP, Hartling L, Hamm M, van der Lee JH, Ursum J, Offringa M (2009) StaR Child Health:
an initiative for RCTs in children. Lancet 374:1310–1312
Knottnerus JA, Bouter LM (2001) The ethics of sample size: two-sided testing and one-sided
thinking. J Clin Epidemiol 54:109–110
Lan KKG, DeMets DL (1983) Discrete sequential boundaries for clinical trials. Biometrika
70:659–663
Lehmacher W, Wassmer G (1999) Adaptive sample size calculations in group sequential trials.
Biometrics 55:1286–1290
McKinney RE Jr, Johnson GM, Stanley K, Yong FH, Keller A, O’Donnell KJ, Brouwers P,
Mitchell WG, Yogev R, Wara DW, Wiznia A, Mofenson L, McNamara J, Spector SA (1998)
A randomized study of combined zidovudine-lamivudine versus didanosine monotherapy in
children with symptomatic therapy-naive HIV-1 infection. The Pediatric AIDS Clinical Trials
Group Protocol 300 Study Team. J Pediatr 133:500–508
Moye LA, Tita AT (2002) Hypothesis testing complexity in the name of ethics: response to
commentary. J Clin Epidemiol 55:209–211
Nyman Y, Von HK, Palm C, Eksborg S, Lonnqvist PA (2006) Etomidate-Lipuro is associated with
considerably less injection pain in children compared with propofol with added lidocaine. Br J
Anaesth 97:536–539
O’Brien PC, Fleming TR (1979) A multiple testing procedure for clinical trials. Biometrics
35:549–556
Ogungbenro K, Aarons L (2008) How many subjects are necessary for population pharmacoki-
netic experiments? Confidence interval approach. Eur J Clin Pharmacol 64:705–713
Pampallona S, Tsiatis AA (1994) Group sequential designs for one-sided and two-sided hypothesis
testing with provision for early stopping in favor of the null hypothesis. J Stat Plan Infer
42:19–35
Peto R, Baigent C (1998) Trials: the next 50 years. Large scale randomised evidence of moderate
benefits. BMJ 317:1170–1171
Pocock SJ (1977) Group sequential methods in the design and analysis of clinical trials.
Biometrika 64:191–199
Rosenberger WF, Huc F (2004) Maximizing power and minimizing treatment failures in clinical
trials. Clin Trials 1:141–147
Sackett DL, Cook DJ (1993) Can we learn anything from small trials? Ann NY Acad Sci
703:25–31
Sammons HM (2011) Avoiding clinical trials in children. Arch Dis Child 96:291–292
Schulz KF, Grimes DA (2005) Sample size calculations in randomised trials: mandatory and
mystical. Lancet 365:1348–1353
Sebille V, Bellissant E (2000) Comparison of four sequential methods allowing for early stopping
of comparative clinical trials. Clin Sci (Lond) 98:569–578
Sebille V, Bellissant E (2003) Sequential methods and group sequential designs for comparative
clinical trials. Fundam Clin Pharmacol 17:505–516
Simes RJ (1995) Prospective meta-analysis of cholesterol-lowering studies: the Prospective
Pravastatin Pooling (PPP) Project and the Cholesterol Treatment Trialists (CTT) Collabora-
tion. Am J Cardiol 76:122C–126C
Smith GC, Pell JP (2003) Parachute use to prevent death and major trauma related to gravitational
challenge: systematic review of randomised controlled trials. BMJ 327:1459–1461
Streiner DL, Norman GR (2008) Health Measurement Scales: a practical guide to their develop-
ment and use. Oxford University Press, Oxford
Tarnow-Mordi WO, Healy MJ (1999) Distinguishing between “no evidence of effect” and
“evidence of no effect” in randomised controlled trials and other comparisons. Arch Dis
Child 80:210–211
Twisk JWR (2003) Applied longitudinal data analysis for epidemiology; a practical guide.
Cambridge University Press, Cambridge
van der Lee JH, Wesseling J, Tanck MW, Offringa M (2008) Efficient ways exist to obtain the
optimal sample size in clinical trials in rare diseases. J Clin Epidemiol 61:324–330
van der Lee JH, Tanck MW, Wesseling J, Offringa M (2009) Pitfalls in the design and analysis of
paediatric clinical trials: a case of a ‘failed’ multi-centre study, and potential solutions. Acta
Paediatr 98:385–391
van der Lee JH, Wesseling J, Tanck MW, Offringa M (2010) Sequential design with boundaries
approach in pediatric intervention research reduces sample size. J Clin Epidemiol 63:19–27
van Houwelingen HC (1999) On “Bayesian monitoring. . .”. J Clin Epidemiol 52:713–714
van Woensel JB, van Aalderen WM, de Weerd W, Jansen NJ, van Gestel JP, Markhorst DG, van
Vught AJ, Bos AP, Kimpen JL (2003) Dexamethasone for treatment of patients mechanically
ventilated for lower respiratory tract infection caused by respiratory syncytial virus. Thorax
58:383–387
Vickers AJ (2003) Underpowering in randomized trials reporting a sample size calculation. J Clin
Epidemiol 56:717–720
Vickers AJ, Altman DG (2001) Statistics notes: analysing controlled trials with baseline and
follow up measurements. BMJ 323:1123–1124
von Goedecke A, Brimacombe J, Hormann C, Jeske HC, Kleinsasser A, Keller C (2005) Pressure
support ventilation versus continuous positive airway pressure ventilation with the ProSeal
laryngeal mask airway: a randomized crossover study of anesthetized pediatric patients.
Anesth Analg 100:357–360
Wald A (1947) Sequential analysis. Wiley, New York
Wassmer G (2000) Basic concepts of group sequential and adaptive group sequential test
procedures. Stat Pap 41:253–279
Whitehead J (1997) The design and analysis of sequential clinical trials. Wiley, Chichester
Whitehead J, Jones DR (1979) The analysis of sequential clinical trials. Biometrika 66:
443–452
Whitehead J, Stratton I (1983) Group sequential clincial trials with triangular continuation regions.
Biometrics 39:227–236
Woods JR, Williams JG, Tavel M (1989) The two-period crossover design in medical research.
Ann Intern Med 110:560–566
Sample Collection, Biobanking, and Analysis
Maurice J. Ahsman, Dick Tibboel, Ron A.A. Mathot, and Saskia N. de Wildt
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
2 Sample Types and Collection Techniques . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
2.1 Blood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 204
2.2 Urine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 205
2.3 Saliva . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
2.4 Breath Samples . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 206
2.5 Meconium . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
2.6 Hair . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 207
3 Leftover Material and Biobanking . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 208
4 Storage and Shipping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
5 Drug Assays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 209
5.1 Assay Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 210
5.2 Sample Preparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 211
5.3 Multiple Drug Assays . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
5.4 Alternative Drug Matrices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 212
6 Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 213
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 214
Abstract Pediatric pharmacokinetic studies require sampling of biofluids from

neonates and children. Limitations on sampling frequency and sample volume com-
plicate the design of these studies. In addition, strict guidelines, designed to guarantee
patient safety, are in place. This chapter describes the practical implications of sample
collection and their storage, with special focus on the selection of the appropriate type
M.J. Ahsman • R.A.A. Mathot

Department of Clinical Pharmacy, Erasmus MC, Rotterdam, The Netherlands
D. Tibboel • S.N. de Wildt (*)
Intensive Care and Department of Pediatric Surgery, Erasmus MC Sophia Children’s Hospital,
Dr. Molewaterplein 60, 3015 GJ Rotterdam, The Netherlands
e-mail: s.dewildt@erasmusmc.nl

204 M.J. Ahsman et al.
of biofluid and withdrawal technique. In addition, we describe appropriate measures

for storage of these specimens, for example, in the context of biobanking, and the
requirements on drug assay methods that they pose.
Pharmacokinetic studies in children are possible, but they require careful selec-
tion of an appropriate sampling method, specimen volume, and assay method. The
checklist provided could help prospective researchers with the design of an appro-
priate study protocol and infrastructure.
Keywords Pediatric • Biobank • Sampling • Blood • Meconium • Saliva •

Drug assay
1 Introduction
The ICH guidelines on pediatric drug studies (Anonymous 2000, 2001a) emphasize
patient safety, which has consequences for the volume of, and methods for,
sampling of biofluids. This has consequences for pharmacokinetic studies in chil-
dren by imposing challenges upon sample collection and drug analysis. The main
questions are as follows:
• Which biological specimen can be used and how can this specimen be collected
in the intended study population?
• What are the maximum allowed sample volumes per occasion and per study
period?
• By what methods can we store samples and acquire reliable drug concentrations?
In this chapter, we discuss these questions and aim to provide practical solutions
and examples to help those planning pharmacokinetic studies in children. The
details of designing population PK studies are outside the scope of this chapter
and are discussed elsewhere.
2 Sample Types and Collection Techniques
2.1 Blood
Extensive blood sampling for traditional pharmacokinetic analysis is usually not

possible in this population for ethical and practical reasons. No official guidelines
exist on the maximum amount of blood that can be sampled in pediatric studies.
However, several guidelines accept a maximum of 3–5% of the total blood volume
per 4 weeks (Anonymous 2004, 2008). In case of simultaneous trials, the recom-
mendation of 3–5% remains the maximum. In addition, repeated blood sampling in
children by repeated punctures can be considered nonethical due to associated pain,
anxiety, and distress. Safety can be improved by reducing the burden associated
Sample Collection, Biobanking, and Analysis 205
with invasive blood sampling and by using methods aimed to reduce the blood
volume needed for drug analysis. In children, blood for pharmacokinetic analysis is
preferably sampled from indwelling central venous or arterial catheters, already in
place for clinical care. Sampling from these catheters is easy, causes only minimal
or no discomfort, and allows for sufficient sample volume collections. Risks
associated with the use of these catheters are bloodstream-related infections and
unintended blood loss. If these catheters are not already in place for clinical
purposes, placement of these catheters solely for research purposes is usually not
considered acceptable by research ethics committees and/or patients and their
family. Alternatively, blood can be sampled from peripherally inserted catheters.
Insertion of these catheters solely for research purposes is sometimes acceptable,
more specifically in the context of therapeutic drug trials. The main limitation,
especially in neonates, is that blood draws are difficult if not impossible from small
bore catheters as used in this population. To overcome this problem, blood can be
taken from heel prick or venepuncture, the latter being much less painful, prefera-
bly when done together with regular blood work. When combining research blood
sampling with regular blood work, the burden for the child may be considered
acceptable both by children and their parents as well as by research ethics
committees. Disadvantages of heel prick samples are the limitation in the volume,
timing of blood samples, and painfulness. In general, blood volumes sampled per
heel prick are limited to 0.5–0.6 ml, including blood collected for regular clinical
blood work. Hence, blood volumes needed for pharmacokinetic analysis should
preferably not exceed 0.2–0.3 ml per sample. In addition, timing of sampling is
restricted if it needs to coincide with clinical blood sampling. Consequently,
extensive and timed sampling for a full pharmacokinetic washout curve is not
possible using this method.
A more detailed and practical guide for different blood sampling methods in
children and neonates has been published by the UK Medicine for Children
Research Network (Hawcutt et al. 2008).
2.2 Urine
For renally cleared drugs, urine sampling may provide an alternative to blood for the
estimation of pharmacokinetics. Also, urinary excretion of the drug and its metabolites
may provide valuable insight into developmental changes in drug metabolism and
excretion (Streetman et al. 2001; Allegaert et al. 2006; Tucker et al. 1998). From a
pharmacokinetic standpoint, the preferred method to collect urine is by urinary
catheter or by direct collection in older children. Using a catheter facilitates complete
urine collection over predefined time periods. A major limitation of the use of urinary
catheters in children is the burden and risks associated with insertion of the catheter,
such as pain, infection, urethral restriction (mainly in boys), and displacement. Hence,
in general, if a catheter is not already in place for clinical purposes, most research
ethics boards will not approve its use for research purposes only in children. Adhesive
collection bags are also frequently used to collect urine, especially in infants and
neonates (Allegaert et al. 2006). In these younger infants, the repeated use of adhesive
urinary bags may result in skin abrasion. Skin abrasion is not only painful and causes
discomfort; it may also increase the risk of invasive infections in a vulnerable
population. The “gauze/cotton ball method” can be used alternatively. A small
gauze with cling film (the latter facing the diaper material to prevent urine absorption
in the diaper) is put in the diaper and urine is collected by expressing the urine from the
gauze (Fell et al. 1997). In a similar fashion, nonabsorbent diapers can be used (Burke
1995). An important limitation of both the bag and gauze/diaper collection methods is
that complete urine collection is most often not possible. Urine may leak along the bag
into the diaper and not all urine can be expressed from the gauze/diaper. This
limitation can be overcome by weighing the diapers to estimate total urine volume
and to multiply volume with urine drug concentrations to be able to estimate total
urinary drug and/or metabolite excretion.
2.3 Saliva
Saliva can be used as a noninvasive alternative to blood for a significant number of

drugs, e.g., caffeine, anti-HIV drugs, anticonvulsants, digoxine, and codeine
(Drummer 2006). Saliva can also be used for DNA sampling. First, saliva can be
collected by simply asking children to spit in a cup. For DNA sampling, specific
cups are available containing anti-DNAse solutions. Understandably, this method is
only feasible in older children (>8 years of age) who are capable to understand and
follow simple instructions.
Younger children can chew on a gauze, cotton “salivette,” or a cotton-cellulose
eyespear, from which saliva can be extracted. Citric acid containing products may
stimulate saliva production and enhance collection. Several commercially available
methods for saliva collection are available (Drummer 2006). In preterm infants,
commercially available products, such as salivettes, are difficult to use. First, the cotton
swab provided is relatively large to be inserted in the mouth. Also, the saliva volume
needed to extract enough saliva from the cotton is considerably higher than can be
sampled from preterms. Before deciding to use one of these methods, it is important to
validate the intended method by studying the correlation between blood concentrations
and saliva concentrations. Saliva drug concentrations may vary according to method
used, with or without citric acid (de Wildt et al. 2001; Strazdins et al. 2005).
2.4 Breath Samples
Breath tests using stable or radioactive isotopes are used in the context of drug
metabolism studies (Paine et al. 2002; de Wildt et al. 2007). Breath sampling of
exhaled labeled CO2 is easiest when children can follow instructions to breathe in a
balloon, from which breath samples can be taken. In younger or critically ill
children, this approach is obviously not feasible. The original collection method
of respiratory CO2 used in children, including neonates, occurs via trapping of CO2
in sodium hydroxide. This method involves a tight-fitting face mask and passing of
the expired air through a condenser containing sodium hydroxide (Pons et al. 1988).
This is impractical and difficult in neonates. Alternatively, a direct nasopharyngeal
sampling technique can be used (van der Schoor et al. 2004). This technique allows
for direct sampling from the nasopharynx using a gastric tube attached to a syringe
or direct attachment of a syringe to a side-port of the endotracheal tube. During
observed expiration, the researcher collects air by pulling the syringe. The collected
air is then transferred to a vacuum tube for laboratory analysis.
2.5 Meconium
By accumulating from the 12th gestational week until birth, meconium acts as a
reservoir for exogenous compounds, such as drugs and metabolites. Drugs are
incorporated into meconium through swallowing drug-contaminated amniotic
fluid or via biliary excretion. Meconium analysis is thought to detect maternal
drug use during the second and third trimesters. Meconium passage occurs in the
first 1–3 days after birth, but may be prolonged in preterm infants. Collection of
meconium from diapers is easy, by scraping meconium from the diaper. 0.5–1 g of
meconium is usually enough for toxicological, quantitative analysis. Contamination
of meconium with urine may occur, which obscures the results. After collection,
meconium can be stored at low temperatures ( 20 C). Storage at room temperature
may reduce the concentrations of drug by degradation. Due to its complex compo-
sition, consisting of epithelial cells, swallowed amniotic fluid, bile salts, lipids,
other endogenous compounds, and xenobiotics until birth, extraction of drugs is
difficult (Gray et al. 2009).
2.6 Hair
Drugs can be incorporated in hair through blood supply of the hair, by external
exposure (through, e.g., smoke) or through secretion from sweat and sebum adja-
cent to the hair follicle.
Hair samples are mainly used for toxicological screening in prenatal alcohol and
drug exposure.
These samples are best collected from the back of the head. The proximal zone
(i.e., the zone which is closer to the root) should be clearly indicated if segmental
analysis is to be performed. The sample can then be stored and transported light and
moisture protected at room temperature. Since hair grows about 1 cm per month,
segmental analysis can be done to estimate the time window of drug exposure
(Gallardo and Queiroz 2008).
3 Leftover Material and Biobanking
In addition to freshly collected blood samples in the context of a single pharmaco-

kinetic study, the use of leftover or previously stored blood samples should be
considered.
This may significantly reduce the burden to the individual child participating in
a trial.
For example, leftover material from regular patient blood work could be used for
pharmacokinetic analysis of drugs that the patient is taking therapeutically. As the
sample volume available will likely be small, very sensitive analytical techniques,
to be described below, are required. This approach has several advantages. First, the
pharmacokinetic results will reflect the real-life clinical situation, as the drug is
studied in the population that actually needs the drug for treatment. Second, the
need for additional blood sampling is limited or nonexistent, which can signifi-
cantly reduce the burden to individual patients. This may even result in a higher
informed consent rate from the child and/or his parents to participate in the study.
Secondly, blood could be sampled routinely for biobanking purposes from all
consenting children/parents on a specific ward or with a predefined disease for later
studies, provided blood sample volumes are within acceptable limits. In this
context, biobanking is defined as collection of biological material and the
associated data and information stored in an organized system, for a population
or a large subset of a population.
This approach is taken in large-scale pharmacogenetic studies in the adult
population. Anonymous linking of clinical data may provide researchers with
ample opportunity to study multiple research questions. Ethics committees and
subjects will generally be amenable to long-term sample storage for future research,
provided that there are sufficient assurances that stringent processes and standards
for patient privacy/confidentiality are in place.
When previously collected samples are necessary to perform a new study, it may
still be possible to obtain consent from the original participants. However, the
consent procedure may vary depending on the source of original data and the
intended purpose; see Helgesson et al. (2007) and Hoeyer et al. (2005) for a
discussion on the ethical aspects of using these data. Some have advocated the
renewal of consent once former study participants reach adulthood, particularly
because the sharing of genetic and phenotypic data could have consequences that
were unforeseen at the time of parental consent decades earlier (Farin et al. 1999).
Although not related to biological fluids, the use of digital leftover material, i.e., the
combination of existing pharmacokinetic datasets from medical literature, may
significantly reduce the need for prospective pharmacokinetic trials. This could,
for instance, be used to study the effect of age and other covariates in the pediatric
population (Ince et al. 2009; de Wildt and Knibbe 2009).
4 Storage and Shipping
According to the Good Clinical Laboratory Practice (GCLP) guidelines issued by

the World Health Organization (Anonymous 2009), samples should be kept “in
such a way as to ensure the integrity and accessibility to the material retained.” GCP
guidelines state that national legislation determines the minimum period during
which data records and material should be stored. The samples should be stored to
allow (re-) examination, but only for as long as the quality permits evaluation, i.e.,
for as long as analyte levels can be reliably requantified without excessive degra-
dation. This requires simulation of average and worst-case conditions in sampling,
storage, and shipping to see the effects on sample integrity. The consequences of
different storage and handling protocols for the analytical results of each type of
sample is too big a topic to be discussed in this brief overview; the reader is referred
to the excellent review by Mehta regarding preanalytical considerations in drug
assays (Mehta 1989).
A major issue in GCP is the protection of subject confidentiality, which should
be maintained not only in reports of final results but also in the preceding steps, i.e.,
during storage, shipping, and drug assay. This requires storage in coded vials, with
access to the original subject data restricted to specific individuals (usually the
researchers directly involved in sampling, storage, and data extraction). To main-
tain sample integrity, appropriate measures should be taken to guarantee the right
temperature, protection from light, etc., throughout the preassay period. These
measures might, for instance, include the use of refrigerators or freezers with
continuous temperature registration and should include standard operating
procedures (SOP) describing responsibilities of the individuals involved in sam-
pling and shipping.
For more information on the GCLP guidelines, the reader is referred to Ezzelle
et al. (2008) and Anonymous (2009). Practical examples of necessary measures can
be found in Peakman and Elliott (2008), Elliott and Peakman (2008), Mehta (1989),
and Vaught (2006).
5 Drug Assays
Quantification of analytes in pediatric studies is complicated by the limited avail-

ability (both in numbers and volume) of biological specimens. The analytical
methods should therefore be sensitive enough to quantify compounds in complex
mixtures (such as blood, plasma, or cerebrospinal fluid) in sample volumes of 10 to
maximum 100 mL. Ideally, these so-called microassays can be used to quantify
different analytes of interest in the same sample, e.g., drugs and their metabolites or
combinations of coadministered drugs.
5.1 Assay Methods
The required sensitivity can be reached using mass spectrometric techniques such
as liquid (LC-MS) or gas (GC-MS) chromatography–mass spectrometry. These
techniques rely on chromatographic separation of analytes from each other and
from matrix components, followed by ionization and counting of analytes of a
selected molecular mass. Compounds of similar mass can be distinguished via mass
filters that allow a single analyte to be selected in the presence of other drugs,
metabolites, or endogenous compounds. To enhance selectivity even further, the
selected compounds can be subsequently fragmented by collision with an inert gas.
This leads to molecular fragments that are highly specific for the original drug or
metabolite. After selection of one of these fragments via another mass filter, the
compound of interest can be quantified. This is called tandem mass spectrometry or
MS/MS (Fig. 1). The mass spectrometric techniques carry a distinct advantage over
other sensitive assays such as enzyme-linked assay, fluorometric assay, and
radioassay. Whereas the latter often suffer from cross-reactivity between structur-
ally related compounds such as drugs and their metabolites or endogenous
substrates (Tribut et al. 2005; Moyer et al. 1986; de Paula et al. 1998; Premaud
et al. 2006; Tate and Ward 2004), the mass spectrometric methods allow
Sample
Sample preparation
Chromatography /
Electrophoresis
Mass spectrometer
Inert gas
F1, F2, F3
M1 F1
Mass filter Mass filter Detector
Fig. 1 Principle of liquid or gas chromatography with tandem mass spectrometry detection. The
sample is cleaned up for chromatographic separation of drugs and metabolites from matrix
components. After chromatography or electrophoresis, the effluent enters the mass spectrometer.
After selection of molecules of a specific molecular weight (M1) by the first mass filter, the
molecules are fragmented with an inert gas. The resulting fragments (F1, F2, and F3) are
sent through the second filter in which one individual fragment is selected to be quantified at
the detector
simultaneous quantification of different analytes in a single run by rapidly changing

the mass filter settings (Marzo and Bo 2007; Vogeser 2003). Another separation
method, which can be used in combination with mass spectrometric detection with
small sample volumes (especially for different drug enantiomers), is capillary
electrophoresis (CE-MS) (Chen and Chen 1999; Sung and Chen 2006), but due to
wide experience and superior sensitivity, LC-MS and GC-MS remain the
cornerstones of drug microassays. Whereas urine and serum or plasma are the
main biofluids in experimental pharmacology, some biochemical markers and
compounds can also be quantified in extracts from dried blood spots. This poses
additional requirements on the assay method and its validation, drug or metabolite
stability, and the availability of reference values for drugs concentrations in whole
blood (see Spooner et al. 2009; Edelbroek et al. 2009). Nevertheless, the logistical
advantages are appealing. Dried bloodspot collection allows sampling at remote
locations, if necessary even by patients or parents themselves. Once dry, the blood
spots can be sent via regular mail services to a central laboratory, without many
additional measures to minimize biohazard. Even samples from large multinational
studies can then be processed at a single laboratory, which greatly improves
efficiency regarding method validation at different study sites, refrigeration or
freezing during sample storage and transport, reliability of assay results due to
increased experience with the assay, and reduction of interlaboratory variability,
etc. Re-assay, however, is usually not possible, since most methods require the
entire dried drop of blood to be processed. So far, there are few published assay
methods with dried blood spots, but their number seems to be increasing; examples
include the quantification of topiramate (la Marca et al. 2008), everolimus (van der
Heijden et al. 2008), tacrolimus (Hoogtanders et al. 2007), metformin (Aburuz et al.
2006), and antiretroviral drugs (Koal et al. 2005).
5.2 Sample Preparation
Exogenous and endogenous components in the biological matrix can interfere with
sample preparation or quantification, which compromises accuracy and precision.
The mechanisms of these so-called matrix effects are not fully understood, but have
been linked to coelution of different compounds (including inorganic ions and
plasma phospholipids) that can interfere with analyte ionization (Taylor 2005;
Careri and Mangia 2006). The degree of signal enhancement or suppression
could therefore vary from individual to individual, but also within individuals
upon changes in physiological constitution, either due to disease progression or
growth and maturation. This implies that validation of the assays should include an
evaluation of matrix effects in biological specimens (“blank matrix”) from the
intended patient population. The US Food and Drug Administration has issued
guidelines on the validation requirements for bioanalytical chromatographic
methods (Anonymous 2001b) without mentioning a specific method to assess
matrix effects; current reports on new LC-MS and GC-MS assays often contain a
qualitative visual assessment or a quantitative calculation based on work by

Matuszewski et al. (Matuszewski et al. 2003; Matuszewski 2006).
Samples are cleaned up via solid phase extraction (SPE) or liquid–liquid extrac-
tion (LLE) to separate analytes from interfering components and, if possible, to
concentrate the analyte in a smaller volume to increase sensitivity (Hyotylainen
2009; Hernandez-Borges et al. 2007). In pediatric and neonatal studies in particular,
sample volumes are small. When volumes become too small to reliably be trans-
ferred from one vial to another, sample preparation can be a challenge, and preassay
concentration in a smaller volume is impossible. Therefore, microassays often
contain minimal sample preparation (i.e., protein precipitation or direct injection,
also called “dilute-and-shoot”) and rely heavily on the chromatographic prowess
of LC-MS or GC-MS equipment to maintain accuracy and precision without
matrix effects. When extensive cleanup cannot be avoided, it is possible to use
LLE with minimal amounts of organic solvents or sophisticated and expensive
microtechniques such as 96-well SPE (Saito and Jinno 2003; Shen et al. 2006;
Ahsman et al. 2010).
5.3 Multiple Drug Assays
The efficiency of pharmacological studies can sometimes be increased by

quantifying multiple analytes in a single sample, since it requires less biological
material per patient while reducing the total analytical workload. Multiple-analyte
assays have been developed for drugs and their main metabolites (Witjes et al.
2009; Liang et al. 2009; Patel et al. 2009) and for drugs from different therapeutic
classes that are often coprescribed in specific patient populations (Ahsman et al.
2009; de Velde et al. 2009; Gomes et al. 2008). Especially for biobanked samples,
these assays can be used to maximize scientific output from limited sample
volumes. This requires careful selection of sampling times in relation to the
expected dose regimens to allow reliable estimation of pharmacokinetic
parameters.
5.4 Alternative Drug Matrices
For studies on fetal drug or pollutant exposure, compounds are assayed in unusual
biological matrices such as meconium, hair, or cord blood. For these biofluids, it
may be even more difficult to find suitable blank material. For meconium in
particular, special sample preparation methods may be necessary to prepare
solutions that are suitable for LC-MS or GC-MS analysis. See Gray et al. (2009),
Rigourd et al. (2008), Frison et al. (2008), Kacinko et al. (2008), and Yeh et al.
(2009) for examples of analytical methods that were developed specifically for
these matrices.
6 Conclusion
In summary, pharmacological studies in children are possible, but require careful

selection of an appropriate sampling method and sample volume. An assay method
should be developed and validated, with special attention to the required sensitivity
level, matrix effects, and sample preparation. See Table 1 for a checklist with the
main points that should be addressed when designing a pediatric study.
Table 1 Items to be considered before engaging in a pediatric study involving sample collection
and drug quantification
Sample collection
What are the maximum allowed sample volumes per occasion and per study period?
Which sampling times are informative (based on population PK study design) and practical?
Is blood the preferred biological specimen or can alternatives be used?
How much sample is required, taking into account the intended assay requirements and potential
future studies into different analytes with leftover material?
Which sampling methods are suitable?
Can these methods be implemented as part of routine clinical procedures and/or do involved staff
need extra training?
Biobanking and leftover samples
Have patients or their guardians given permission for biobanking and use of leftover samples?
Is there a separate long-term storage facility with temperature control, compliant with GCP
guidelines available?
How are patient data being recorded; is the database suitable for (anonymized) long-term storage
and extraction?
Who decides whether to grant individual researchers access to samples and data, and is there a
system that allows tracking of individual samples and researchers that use them?
Which departments or individuals are responsible for maintenance, logging access rights to
samples, etc?
Shipping and storage
How stable are the biofluid specimens and analytes at standard storage conditions: ambient
temperature (20–25 C), refrigerated (4–7 C), frozen ( 20 C), and deep-frozen ( 80 C)?
What are the average and worst-case shipping conditions and time?
Is privacy of study participants guaranteed during storage and shipping?
What arrangements have been made to allow sampling, storage, and processing outside standard
working hours, in weekends, and on holidays?
Have roles and responsibilities been agreed upon by the clinical department, logistical services,
and the laboratory?
Have standard operating procedures (SOP) containing contact details, storage conditions, etc.,
been agreed upon by and made available to the involved staff?
Assay
How much sample is required for the assay, taking into account reassay in case of instrument
failure?
Are the expected concentrations within the assay’s calibration range?
Has the assay been validated for this specific type of sample and analyte?
Have matrix effects been evaluated in appropriate batches of blank matrix? (preferably from
patients of the intended age, comedication, and disease state)
References
Aburuz S, Millership J, McElnay J (2006) Dried blood spot liquid chromatography assay for
therapeutic drug monitoring of metformin. J Chromatogr B Analyt Technol Biomed Life Sci
832:202–207
Ahsman MJ, Wildschut ED, Tibboel D, Mathot RA (2009) Microanalysis of beta-lactam
antibiotics and vancomycin in plasma for pharmacokinetic studies in neonates. Antimicrob
Agents Chemother 53:75–80
Ahsman MJ, Van der Nagel BC, Mathot RA (2010) Quantification of midazolam, morphine and
metabolites in plasma using 96-well solid-phase extraction and ultra-performance liquid
chromatography-tandem mass spectrometry. Biomed Chromatogr 24(9):969–976
Allegaert K, Rayyan M, de Hoon J, Tibboel D, Verbesselt R, Naulaers G, Van den Anker JN,
Devlieger H (2006) Contribution of glucuronidation to tramadol disposition in early neonatal
life. Basic Clin Pharmacol Toxicol 98:110–112
Anonymous (2000) E11: Guidance for industry – clinical investigation of medicinal products in
the pediatric population. US Food and Drug Administration, Center for Drug Evaluation and
Research, Rockville, MD
Anonymous (2001a) Clinical investigation of medicinal products in the paediatric population, vol
E11. European Medicines Agency, London
Anonymous (2001b) Guidance for industry – bioanalytical method validation. Biopharmaceutics
Coordinating Committee, Center for Drug Evaluation and Research, US Food and Drug
Administration, Rockville, MD
Anonymous (2004) The Hospital for Sick Children (SickKids) Research Ethics Board Blood
Sampling Guidelines. Toronto
Anonymous (2008) E11: Ethical considerations for clinical trials on medicinal products with the
paediatric population. Guidelines for Directive 2001/20/EC. European Commission, Brussels
Anonymous (2009) Good Clinical Laboratory Practice (GCLP). World Health Organization
Special Programme for Research and Training in Tropical Disease. WHO, Geneva
Burke N (1995) Alternative methods for newborn urine sample collection. Pediatr Nurs
21:546–549
Careri M, Mangia A (2006) Validation and qualification: the fitness for purpose of mass
spectrometry-based analytical methods and analytical systems. Anal Bioanal Chem 386:38–45
Chen SH, Chen YH (1999) Pharmacokinetic applications of capillary electrophoresis. Electropho-
resis 20:3259–3268
de Paula M, Saiz LC, Gonzalez-Revalderia J, Pascual T, Alberola C, Miravalles E (1998)
Rifampicin causes false-positive immunoassay results for urine opiates. Clin Chem Lab Med
36:241–243
de Velde F, Alffenaar JW, Wessels AM, Greijdanus B, Uges DR (2009) Simultaneous determina-
tion of clarithromycin, rifampicin and their main metabolites in human plasma by liquid
chromatography-tandem mass spectrometry. J Chromatogr B Analyt Technol Biomed Life
Sci 877:1771–1777
de Wildt SN, Knibbe CA (2009) Knowledge of developmental pharmacology and modeling
approaches should be used to avoid useless trials in children. Eur J Clin Pharmacol
65:849–850, author reply 851–842
de Wildt SN, Kerkvliet KT, Wezenberg MG, Ottink S, Hop WC, Vulto AG, van Den Anker JN
(2001) Use of saliva in therapeutic drug monitoring of caffeine in preterm infants. Ther Drug
Monit 23:250–254
de Wildt SN, Berns MJ, van den Anker JN (2007) 13C-erythromycin breath test as a noninvasive
measure of CYP3A activity in newborn infants: a pilot study. Ther Drug Monit 29:225–230
Drummer OH (2006) Drug testing in oral fluid. Clin Biochem Rev 27:147–159
Edelbroek PM, van der Heijden J, Stolk LM (2009) Dried blood spot methods in therapeutic drug
monitoring: methods, assays, and pitfalls. Ther Drug Monit 31:327–336
Elliott P, Peakman TC (2008) The UK Biobank sample handling and storage protocol for the
collection, processing and archiving of human blood and urine. Int J Epidemiol 37:234–244
Ezzelle J, Rodriguez-Chavez IR, Darden JM, Stirewalt M, Kunwar N, Hitchcock R, Walter T,
D’Souza MP (2008) Guidelines on good clinical laboratory practice: bridging operations
between research and clinical research laboratories. J Pharm Biomed Anal 46:18–29
Farin D, Kitzes-Cohen R, Piva G, Gozlan I (1999) High performance liquid chromatography
method for the determination of meropenem in human plasma. Chromatographia 49:253–255
Fell JM, Thakkar H, Newman DJ, Price CP (1997) Measurement of albumin and low molecular
weight proteins in the urine of newborn infants using a cotton wool ball collection method.
Acta Paediatr 86:518–522
Frison G, Favretto D, Vogliardi S, Terranova C, Ferrara SD (2008) Quantification of citalopram or
escitalopram and their demethylated metabolites in neonatal hair samples by liquid chroma-
tography-tandem mass spectrometry. Ther Drug Monit 30:467–473
Gallardo E, Queiroz JA (2008) The role of alternative specimens in toxicological analysis. Biomed
Chromatogr 22:795–821
Gomes NA, Vaidya VV, Pudage A, Joshi SS, Parekh SA (2008) Liquid chromatography-tandem
mass spectrometry (LC-MS/MS) method for simultaneous determination of tenofovir and
emtricitabine in human plasma and its application to a bioequivalence study. J Pharm Biomed
Anal 48:918–926
Gray TR, Shakleya DM, Huestis MA (2009) A liquid chromatography tandem mass spectrometry
method for the simultaneous quantification of 20 drugs of abuse and metabolites in human
meconium. Anal Bioanal Chem 393:1977–1990
Hawcutt DB, Rose AC, Nunn T, Turner MA (2008) NIHR Medicines for Children Research
Network (MCRN): points to consider when planning the collection of blood samples in clinical
trials of investigational medicinal products. MCRN Guide. NIHR, London
Helgesson G, Dillner J, Carlson J, Bartram CR, Hansson MG (2007) Ethical framework for
previously collected biobank samples. Nat Biotechnol 25:973–976
Hernandez-Borges J, Borges-Miquel TM, Rodriguez-Delgado MA, Cifuentes A (2007) Sample
treatments prior to capillary electrophoresis-mass spectrometry. J Chromatogr A
1153:214–226
Hoeyer K, Olofsson BO, Mjorndal T, Lynoe N (2005) The ethics of research using biobanks:
reason to question the importance attributed to informed consent. Arch Intern Med 165:97–100
Hoogtanders K, van der Heijden J, Christiaans M, Edelbroek P, van Hooff JP, Stolk LM (2007)
Therapeutic drug monitoring of tacrolimus with the dried blood spot method. J Pharm Biomed
Anal 44:658–664
Hyotylainen T (2009) Critical evaluation of sample pretreatment techniques. Anal Bioanal Chem
394:743–758
Ince I, de Wildt SN, Tibboel D, Danhof M, Knibbe CA (2009) Tailor-made drug treatment for
children: creation of an infrastructure for data-sharing and population PK-PD modeling. Drug
Discov Today 14:316–320
Kacinko SL, Shakleya DM, Huestis MA (2008) Validation and application of a method for the
determination of buprenorphine, norbuprenorphine, and their glucuronide conjugates in human
meconium. Anal Chem 80:246–252
Koal T, Burhenne H, Romling R, Svoboda M, Resch K, Kaever V (2005) Quantification of
antiretroviral drugs in dried blood spot samples by means of liquid chromatography/tandem
mass spectrometry. Rapid Commun Mass Spectrom 19:2995–3001
la Marca G, Malvagia S, Filippi L, Fiorini P, Innocenti M, Luceri F, Pieraccini G, Moneti G,
Francese S, Dani FR, Guerrini R (2008) Rapid assay of topiramate in dried blood spots by a
new liquid chromatography-tandem mass spectrometric method. J Pharm Biomed Anal
48:1392–1396
Liang X, Li Y, Barfield M, Ji QC (2009) Study of dried blood spots technique for the determination
of dextromethorphan and its metabolite dextrorphan in human whole blood by LC-MS/MS.
J Chromatogr B Analyt Technol Biomed Life Sci 877:799–806
Marzo A, Bo LD (2007) Tandem mass spectrometry (LC-MS-MS): a predominant role in

bioassays for pharmacokinetic studies. Arzneimittelforschung 57:122–128
Matuszewski BK (2006) Standard line slopes as a measure of a relative matrix effect in quantita-
tive HPLC-MS bioanalysis. J Chromatogr B Analyt Technol Biomed Life Sci 830:293–300
Matuszewski BK, Constanzer ML, Chavez-Eng CM (2003) Strategies for the assessment of matrix
effect in quantitative bioanalytical methods based on HPLC-MS/MS. Anal Chem
75:3019–3030
Mehta AC (1989) Preanalytical considerations in drug assays in clinical pharmacokinetic studies.
J Clin Pharm Ther 14:285–295
Moyer TP, Johnson P, Faynor SM, Sterioff S (1986) Cyclosporine: a review of drug monitoring
problems and presentation of a simple, accurate liquid chromatographic procedure that solves
these problems. Clin Biochem 19:83–89
Paine MF, Wagner DA, Hoffmaster KA, Watkins PB (2002) Cytochrome P450 3A4 and
P-glycoprotein mediate the interaction between an oral erythromycin breath test and rifampin.
Clin Pharmacol Ther 72:524–535
Patel BN, Sharma N, Sanyal M, Shrivastav PS (2009) An accurate, rapid and sensitive determina-
tion of tramadol and its active metabolite O-desmethyltramadol in human plasma by LC-MS/
MS. J Pharm Biomed Anal 49:354–366
Peakman TC, Elliott P (2008) The UK Biobank sample handling and storage validation studies. Int
J Epidemiol 37(Suppl 1):i2–i6
Pons G, Blais JC, Rey E, Plissonnier M, Richard MO, Carrier O, d’Athis P, Moran C, Badoual J,
Olive G (1988) Maturation of caffeine N-demethylation in infancy: a study using the 13CO2
breath test. Pediatr Res 23:632–636
Premaud A, Rousseau A, Picard N, Marquet P (2006) Determination of mycophenolic acid plasma
levels in renal transplant recipients co-administered sirolimus: comparison of an enzyme
multiplied immunoassay technique (EMIT) and liquid chromatography-tandem mass spec-
trometry. Ther Drug Monit 28:274–277
Rigourd V, Amirouche A, Tasseau A, Kintz P, Serreau R (2008) Retrospective diagnosis of an
adverse drug reaction in a breastfed neonate: liquid chromatography-tandem mass spectrome-
try quantification of dextropropoxyphene and norpropoxyphene in newborn and maternal hair.
J Anal Toxicol 39:787–789
Saito Y, Jinno K (2003) Miniaturized sample preparation combined with liquid phase separations.
J Chromatogr A 1000:53–67
Shen JX, Tama CI, Hayes RN (2006) Evaluation of automated micro solid phase extraction tips
(micro-SPE) for the validation of a LC-MS/MS bioanalytical method. J Chromatogr B Analyt
Technol Biomed Life Sci 843:275–282
Spooner N, Lad R, Barfield M (2009) Dried blood spots as a sample collection technique for the
determination of pharmacokinetics in clinical studies: considerations for the validation of a
quantitative bioanalytical method. Anal Chem 81:1557–1563
Strazdins L, Meyerkort S, Brent V, D’Souza RM, Broom DH, Kyd JM (2005) Impact of saliva
collection methods on sIgA and cortisol assays and acceptability to participants. J Immunol
Methods 307:167–171
Streetman DS, Kashuba AD, Bertino JS Jr, Kulawy R, Rocci ML Jr, Nafziger AN (2001) Use of
midazolam urinary metabolic ratios for cytochrome P450 3A (CYP3A) phenotyping.
Pharmacogenetics 11:349–355
Sung WC, Chen SH (2006) Pharmacokinetic applications of capillary electrophoresis: a review on
recent progress. Electrophoresis 27:257–265
Tate J, Ward G (2004) Interferences in immunoassay. Clin Biochem Rev 25:105–120
Taylor PJ (2005) Matrix effects: the Achilles heel of quantitative high-performance liquid
chromatography-electrospray-tandem mass spectrometry. Clin Biochem 38:328–334
Tribut O, Gaulier JM, Allain H, Bentue-Ferrer D (2005) Major discrepancy between digoxin
immunoassay results in a context of acute overdose: a case report. Clin Chim Acta
354:201–203
Tucker GT, Rostami-Hodjegan A, Jackson PR (1998) Determination of drug-metabolizing

enzyme activity in vivo: pharmacokinetic and statistical issues. Xenobiotica 28:1255–1273
van der Heijden J, de Beer Y, Hoogtanders K, Christiaans M, de Jong GJ, Neef C, Stolk L (2008)
Therapeutic drug monitoring of everolimus using the dried blood spot method in combination
with liquid chromatography-mass spectrometry. J Pharm Biomed Anal 50(4):664–670
van der Schoor SR, de Koning BA, Wattimena DL, Tibboel D, van Goudoever JB (2004)
Validation of the direct nasopharyngeal sampling method for collection of expired air in
preterm neonates. Pediatr Res 55:50–54
Vaught JB (2006) Blood collection, shipment, processing, and storage. Cancer Epidemiol Biomark
Prev 15:1582–1584
Vogeser M (2003) Liquid chromatography-tandem mass spectrometry – application in the clinical
laboratory. Clin Chem Lab Med 41:117–126
Witjes BC, Ahsman MJ, van der Nagel BC, Tibboel D, Mathot RA (2009) Simultaneous assay of
sildenafil and desmethylsildenafil in neonatal plasma by ultra-performance liquid chromatog-
raphy-tandem mass spectrometry. Biomed Chromatogr 24(2):180–185
Yeh RF, Rezk NL, Kashuba AD, Dumond JB, Tappouni HL, Tien HC, Chen YC, Vourvahis M,
Horton AL, Fiscus SA, Patterson KB (2009) Genital tract, cord blood, and amniotic fluid
exposures of seven antiretroviral drugs during and after pregnancy in human immunodefi-
ciency virus type 1-infected women. Antimicrob Agents Chemother 53:2367–2374
Ethical Considerations in Conducting Pediatric
Research
Michelle Roth-Cline, Jason Gerson, Patricia Bright, Catherine S. Lee,

and Robert M. Nelson
Contents
1 Children as Research Subjects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 220
2 The Principle of Scientific Necessity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 221
3 Appropriate Balance of Risk and Potential Benefit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222
3.1 Component Analysis and Additional Safeguards for Children . . . . . . . . . . . . . . . . . . . . . 224
3.2 Interventions or Procedures that Do Not Offer the PDB . . . . . . . . . . . . . . . . . . . . . . . . . . . . 225
3.3 Interventions or Procedures that Offer the PDB . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 229
4 Selected Ethical Issues in the Design and Conduct of Pediatric Research . . . . . . . . . . . . . . . 231
4.1 Clinical Equipoise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 231
4.2 Choice of Control Group and Placebo Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 232
4.3 Alternatives to Placebo Controlled Trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 234
4.4 Special Concerns in FIH Pediatric Clinical Trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 235
4.5 Data and Safety Monitoring in Pediatric Clinical Trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236
4.6 Compensation for Pediatric Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
5 Child Assent and Parental Permission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
5.1 The Assent Requirement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 237
5.2 Parental Permission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
5.3 The Definition of a Child . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 239
6 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240
Abstract The critical need for pediatric research on drugs and biological products
underscores the responsibility to ensure that children are enrolled in clinical
research that is both scientifically necessary and ethically sound. In this chapter,
we review key ethical considerations concerning the participation of children in
clinical research. We propose a basic ethical framework to guide pediatric research,
and suggest how this framework might be operationalized in linking science and
M. Roth-Cline • J. Gerson • P. Bright • C.S. Lee • R.M. Nelson (*)

U.S. Department of Health and Human Services, Food and Drug Administration, Office of the
Commissioner, Office of Pediatric Therapeutics, Silver Spring, MD 2011, USA
e-mail: Robert.Nelson@fda.hhs.gov

220 M. Roth-Cline et al.
ethics. Topics examined include: the status of children as a vulnerable population;

the appropriate balance of risk and potential benefit in research; ethical con-
siderations underlying study design, including clinical equipoise, placebo controls,
and non-inferiority designs; the use of data monitoring committees; compensation;
and parental permission and child assent to participate in research. We incorporate
selected national (USA) and international guidelines, as well as regulatory
approaches to pediatric studies that have been adopted in the USA, Canada, and
Europe.
Keywords Ethics • Pediatrics • Children • Subpart D • International guidelines •

Extrapolation • Component analysis • Equipoise • Risk assessment • Choice of
control group • Placebo • Minor increase • Scientific necessity • Minimal risk •
Direct benefit • Parental permission • Child assent
1 Children as Research Subjects
Historically, children were viewed as vulnerable subjects who should be protected

from the risks of research. The result was a paucity of safety and effectiveness data
that made the use of therapeutic agents a virtual uncontrolled experiment whenever
they were prescribed for children (American Academy of Pediatrics 1977). Tens of
thousands of children were harmed by therapies that were assumed in the absence
of research to be safe and effective (Fost 1998). More recently, pediatric research
has come to be seen as a moral imperative (Shaddy and Denne 2010). Additionally,
some disorders primarily affect children, necessitating studies to develop therapeu-
tics in these populations.
The vulnerability of children stems from a number of factors (Kipnis 2003).
Children commonly lack mature decision-making capacity; they are subject to the
authority of others; they may defer in ways that can mask underlying dissent; and
their rights and interests may be socially undervalued. As with adults, children may
have acute medical conditions requiring immediate decisions without adequate
time for education and deliberation; they may have serious medical conditions
that cannot be effectively treated; and they may lack important socially distributed
goods that would be provided as a consequence of research participation. Kipnis
suggests that parental permission and child assent procedures alone cannot mitigate
these vulnerabilities. Rather, studies in the pediatric population must be designed to
minimize risk and maximize the possibility of therapeutic benefit (Kipnis 2003).
Recognition of this vulnerability has led many countries to develop regulations
or guidelines specific to research with children. In 1973, the US Department of
Health, Education and Welfare published its first proposals to develop regulations
providing additional protections for vulnerable populations that had “limited
capacities to consent” (Department of Health Education and Welfare 1973). The
problem of regulating research on children was also assessed by the National
Commission (Department of Health Education and Welfare 1978b). The US Food
Ethical Considerations in Conducting Pediatric Research 221
and Drug Administration (FDA) proposed establishing regulations for the pro-
tection of human subjects in 1979, including protections pertaining to clinical
investigations involving children (Department of Health Education and Welfare
1979). In 1981, FDA regulations were promulgated regarding informed consent
(21 CFR Part 50, 2011) and institutional review board (IRB) review of research
(21 CFR Part 56, 2011). Based on recommendations made by the National Com-
mission, regulations were promulgated in 1983 that governed research on children
conducted or funded by the Department of Health and Human Services (Depart-
ment of Health Education and Welfare 1983). In 2001, similar protections were
extended to research regulated by FDA (2001).
Specific guidelines on pediatric research within the European Union were
promulgated in 2001. Directive 2001/20/EC required Member States to develop
laws, regulations, and administrative provisions for the implementation of good
clinical practice in the conduct of clinical trials (European Parliament and the
Council 2001). Specific protections were to be implemented to ensure adequate
protections for minors, including parental permission and assent of able children,
assurance of direct benefit for the child or for the group of patients with the
particular condition, minimization of risk, and scientific necessity of the research.
An ad hoc group responsible for guideline development made further recom-
mendations for implementation of this Directive (2008).
The additional protections for children to be enrolled in a clinical investigation
can be divided into four “nested” domains with each protection building on an
adequate response to the prior protection. The enrollment of children in a clinical
investigation must be considered scientifically necessary before the evaluation of
whether the research interventions or procedures present an appropriate balance
of risk and potential benefit. A clinical investigation must be found to have an
appropriate balance of risk and potential benefit before considering the role of
parental permission and child assent. This chapter will address these four nested
protections.
2 The Principle of Scientific Necessity
A fundamental pillar of pediatric research is the ethical principle of “scientific

necessity.” This principle holds that children should not be enrolled in a clinical
investigation unless necessary to achieve an important scientific and/or public
health objective concerning the health and welfare of children. An “important
scientific question” may be one that generates information that is necessary and
timely for establishing the appropriate pediatric use of investigational therapeutics.
A corollary is that children should not be enrolled in studies that are duplicative
or unlikely to yield important knowledge applicable to children about the product or
condition under investigation. These principles are grounded in regulations and/or
guidelines governing human subject protections worldwide. FDA regulations
require that risks to subjects are minimized by eliminating unnecessary procedures
(21 CFR 56.111(a)(1) 2011), and that the selection of subjects must be equitable
(21 CFR 56.111(b) 2011).
Consistent with the recommendations of the National Commission, equitable
selection requires that subjects who are capable of informed consent (i.e., compe-
tent adults) should be enrolled prior to subjects who cannot consent (e.g., children)
(Department of Health Education and Welfare 1978b). There is broad international
agreement on this approach, assuming there are no significant scientific reasons
to enroll younger children preferentially to older children and/or adults. EMA
regulations (2001), International Conference on Harmonisation (ICH) guide-
lines E6 (1996) and E11 (2000), and the Declaration of Helsinki (World Medical
2008) all state explicitly that vulnerable populations such as children should not be
enrolled in a clinical investigation unless their involvement is essential to answer a
scientific objective relevant to the health and welfare of that vulnerable population.
The ethical principle of “scientific necessity” has been operationalized in the
scientific principle of “extrapolation.” As described in the Pediatric Research
Equity Act of 2007 “if the course of the disease and the effects of the drug are
sufficiently similar in adults and pediatric patients, the Secretary may conclude that
pediatric effectiveness can be extrapolated from adequate and well-controlled
studies in adults, usually supplemented with other information obtained in pediatric
patients, such as pharmacokinetic studies” (Food and Drug Administration Amend-
ments Act of 2007). The principle of extrapolation also can be found in the
International Conference on Harmonization guidance on pediatric research (ICH
2000). The need for pediatric studies is assessed by asking a series of questions
about the similarity of the adult and pediatric disease, response to treatment, drug-
exposure response, and pharmacokinetic and pharmacodynamic measurements that
could be used to predict efficacy (see Fig. 1).
3 Appropriate Balance of Risk and Potential Benefit
The additional safeguards for children enrolled in research are based on two ethical
principles. First, the risks to which children would be exposed must be low if there
is no prospect of direct therapeutic benefit (PDB) to the enrolled children. Second,
children should not be placed at a disadvantage by being enrolled in a clinical trial,
either through exposure to excessive risks or by failing to get necessary health care.
Consequently, the data necessary to initiate a pediatric investigation must demon-
strate either an acceptably low risk of the experimental intervention or a sufficient
PDB to justify the risks of the intervention. A major challenge facing the develop-
ment of a new product for the treatment of a pediatric disorder or condition
is bridging this “risk gap” between (a) research involving procedures and/or
interventions that present only a low risk given the absence of sufficient data to
establish the PDB, and (b) the conduct of either “proof of concept” or pivotal trials
for dosing, safety and/or efficacy that offer a sufficient PDB to the enrolled children
to justify exposure to interventions that present greater than low risk.
Fig. 1 FDA algorithm for determining need for pediatric studies using the principle of scientific
necessity/extrapolation
There are several pathways to pediatric licensure of investigational products. If

the product is being developed for a pediatric indication alone (if no comparable
adult indication exists), sufficient preclinical data must be developed to support the
initiation of pediatric clinical trials. In this case, a major hurdle is establishing a
sufficient PDB using a preclinical animal model. If the product is being developed
for an indication that occurs in both children and adults, the goal should be
concurrent licensure unless there are safety concerns that would delay or even
preclude pediatric studies. Adult and pediatric development may proceed either
sequentially or concurrently, depending on the product and factors such as the
anticipated risks to children and availability of alternate treatments. However,
concurrent development still requires sufficient information about PDB in children
to support initiating pediatric trials.
If safety or efficacy results of adult trials are necessary to inform pediatric

development, sequential development may be necessary. Importantly, sequential
development does not necessarily mean that concurrent licensure cannot be
achieved. For example, if a phase 2 study of an antiviral agent showed decreased
viral burden in adult studies, this information may help to provide the proof of
concept necessary to support PDB in children. Dosing and safety studies could then
be performed in children while the pivotal efficacy trial was initiated in adults.
Particularly if the efficacy of the agent was extrapolated to some or all subgroups
of the pediatric population, sufficient pediatric data may be available at the conclu-
sion of the adult phase III studies to support concurrent licensure.
3.1 Component Analysis and Additional Safeguards for Children
For adult subjects, the risks of research participation can be justified either by the
anticipated direct benefits to the subjects or by the importance of the anticipated
knowledge. Investigations involving children that pose more than low risk cannot
be justified by the importance of anticipated knowledge. In pediatric studies, the
allowable risk exposure for an intervention or procedure not offering a PDB must be
restricted to low risk. Thus, the individual research interventions and procedures
that are contained in an investigational protocol must be categorized and assessed
according to whether they do or do not offer PDB – an approach referred to as
“component analysis.”
Component analysis has come under recent criticism for using the norm of
clinical equipoise as the standard for determining the ethical acceptability of
therapeutic interventions or procedures (Miller et al. 2003; Miller and Brody
2007). The concept of clinical equipoise will be discussed more fully below. A
related (albeit unconvincing) criticism of component analysis is directed toward the
manner in which the distinction between therapeutic and non-therapeutic
procedures is made (Wendler and Miller 2007). Wendler and Miller (2007) argue
that the consequences of the intervention are what matters to the determination of
the PDB, rather than the intent of the investigator or the design of the individual
intervention. All parties to the debate agree on the need to avoid the term “thera-
peutic research” which may justify (or offset) the risks of non-beneficial procedures
through the inclusion of unrelated beneficial procedures in the same protocol
(i.e., the fallacy of the “package deal”) (Department of Health Education and
Welfare 1978b; Institute of Medicine 2004; Medical Research Council 2004).
Otherwise a non-beneficial research intervention that presents considerable risk
could be justified by adding unrelated therapeutic components to the protocol, such
as free health care.
The analysis of a proposed clinical investigation can be approached either (1) by
assessing whether or not each intervention or procedure does or does not offer the
PDB, followed by an assessment of the risks of each component, or (2) by assessing
the risks of each intervention and procedure, followed by an assessment of the PDB
for those components that present greater than minimal risk. An intervention or
procedure that presents no more than minimal risk may or may not offer a PDB. We
will discuss the “minimal risk” category under the heading of interventions or
procedures that do not offer the PDB.
3.2 Interventions or Procedures that Do Not Offer the PDB
There is general international consensus that a child’s exposure to risk in pediatric

research must be minimal/low in the absence of direct therapeutic benefit to that
child. Although there are differences in terminology (minimal risk, minor increase
over minimal, low risk, minimal burden, etc.), international regulations share the
ethical commitment to limit a child’s exposure to non-therapeutic risk. General
guidance from European directives is supplemented below by a more detailed
review of the US Code of Federal Regulations (CFR) – exploring the categories
of “minimal risk” and “minor increase over minimal” in the context of no direct
benefit for the individual pediatric participant.
3.2.1 Minimal/Low Risk: No Direct Benefit
For research on non-consenting subjects that does not offer direct therapeutic
benefit, the ICH (1996) E6 Guidelines specify that “the foreseeable risks to the
subjects are low” and that “the negative impact on the subjects’ well-being is
minimized and low.” FDA regulations use the term “minimal risk” (21 CFR
50.51, 2011) and define it as “the probability and magnitude of harm or discomfort
anticipated in the research are not greater in and of themselves than those ordinarily
encountered in daily life or during the performance of routine physical or psycho-
logical examinations or tests” (21 CFR 50.3(k) 2011). This definition appears to
allow for a “relativistic interpretation” indexed to the research participants’ own
experiences as well as provides two comparators for assessing minimal risk (a)
ordinary daily life, and (b) routine physical or psychological examinations or tests
(Institute of Medicine 2004). There is well-documented variability in the interpre-
tation and application of “minimal risk” (Shah et al. 2004; Institute of Medicine
2004; Kopelman 2000).
Three US-based advisory panels – the Institute of Medicine (IOM), The
Secretary’s Advisory Committee on Human Research Protections (SACHRP),
and The National Human Research Protections Advisory Committee – recommend
the international use of a uniform standard for minimal risk (Fisher et al. 2007).
Grounded in the ethical principle of justice as fairness (Institute of Medicine 2004),
this approach indexes minimal risk to the normal experiences of average, healthy
children rather than to risk levels routinely experienced by the research participants.
According to this standard, research interventions and procedures should not
involve potential harm or discomfort beyond that which average, healthy, normal
children may encounter in their daily lives or in routine physical or psychological

examinations or tests (Institute of Medicine 2004). This protects children with a
disorder or condition or children who are at increased risk due, for example, to poor
socioeconomic status from research unrelated to their condition that is considered
greater than minimal risk for a healthy child.
The US-based National Commission listed “routine immunization, modest
changes in diet or schedule, physical examination, obtaining blood and urine
specimens . . .developmental assessments. . . most questionnaires, observational
techniques, noninvasive physiological monitoring, [and] psychological tests and
puzzles” as minimal risk (Department of Health Education and Welfare 1978b).
While not specified here, “obtaining blood” has been understood to mean veni-
puncture in many settings in the USA. Other examples include “obtaining stool
samples, administering electroencephalograms, . . . [and] a taste test of an excip-
ient or tests of devices involving temperature readings orally or in the ear” (Food
and Drug Administration 2001). SACHRP lists a number of physical (e.g.,
measurement of height, weight, and head circumference; assessment of obesity
with skin fold calipers; hearing and vision tests; testing of fine and gross motor
development; non-invasive physiological monitoring) and psychological (e.g.,
child and adolescent intelligence tests; infant mental and motor scales; educa-
tional tests; reading and math ability tests; social development assessment;
family and peer relationship assessments; emotional regulation scales; scales to
detect feelings of sadness or hopelessness) examinations or tests as being no
more than minimal risk (Office for Human Research Protections 2005). Finally,
some limited exposure to radiation from diagnostic procedures may be viewed
as minimal risk (Nelson 2006). However, some of the above procedures may be
considered greater than minimal risk depending on the context of the research
and the specific population to be enrolled (Office for Human Research
Protections 2005).
In assessing for minimal risk, harm or discomfort should be interpreted in
relation to the ages (and developmental status) of the children to be studied
(Institute of Medicine 2004; Department of Health Education and Welfare
1978a). The duration, cumulative risks, and reversibility of harm also impact on
the overall level of risk (Fisher et al. 2007). The use of background risk associated
with daily life as a standard for minimal risk has been the subject of debate (Nelson
2007; Wendler 2009; Wendler and Glantz 2007; Wendler and Miller 2007). Data
about the risks of “daily life” or “routine examinations or tests” contribute to an
informed evaluation of minimal risk, but they alone are not sufficient. The moral
acceptability of the risks of research reflects the obligation of a scrupulous parent to
evaluate and weigh research risks. These risks should be evaluated against the risks
of daily life or routine examinations of a healthy child who is supervised by a
prudent parent (Nelson 2007; Nelson and Ross 2005). Some general risks that
healthy children experience in daily life as part of their growth and development
may be deemed excessive if the risk is introduced only for the purpose of producing
generalizable knowledge (Fisher et al. 2007).
3.2.2 Minor Increase over Minimal Risk: No Direct Benefit
FDA regulations also include a classification of “minor increase over minimal risk”
(21 CFR 50.53, 2011). An intervention or procedure approved under this category
must also involve “experiences to subjects that are reasonably commensurate with
those inherent in their actual or expected. . . situations” and be “likely to yield
generalizable knowledge about the subjects’ disorder or condition that is of vital
importance for the understanding or amelioration of the subjects’ disorder or
condition.” This category has been the most controversial, garnering two dissenting
votes from members of the US National Commission (Department of Health
Education and Welfare 1978b). The justification for this classification has included
that the increased risk is warranted due to scientific necessity (CIOMS 2002;
Institute of Medicine 2004), scrupulous parents can be entrusted with the authority
to evaluate such non-beneficial risk exposures (Nelson and Ross 2005), and that
the absolute difference in risk exposure is meant to be “slight” (Department of
Health Education and Welfare 1978a). The regulations do not, however, define
“disorder or condition,” “vital importance,” “reasonably commensurate,” and
“minor increase over minimal risk.” These concepts are explored below.
The IOM defined “disorder or condition” as a set of “specific physical, psy-
chological, neurodevelopmental, or social characteristics” that scientific evidence
or clinical knowledge has shown to compromise the child’s health or “to increase
risk of developing a health problem in the future” (Institute of Medicine 2004).
Therefore, a child could be healthy, but “at risk” for the condition that is the object
of the research based on scientific and/or clinical evidence. Consistent with
international guidelines, this definition excludes the use of healthy not-at-risk
children from greater than minimal risk research without a PDB (CIOMS 2002;
European Parliament and the Council 2001; ICH 1996). The IOM also understood
the requirement for “vital importance” to be consistent with the principle of
scientific necessity and thus closely tied to the child’s “disorder or condition”
(Institute of Medicine 2004). The overall plan for pediatric product development
should be taken into consideration since information gained from the specific
protocol under consideration may be an important yet intermediate step leading to
further investigations.
The National Commission uses “commensurate” to describe research activities
that are reasonably similar (but need not be identical) to procedures that prospective
research participants may ordinarily experience. The IOM elaborated on this
approach, noting that “although a child might not have experienced a particular
research procedure. . .the procedure could still be described to the child as poten-
tially presenting levels of pain, immobility, anxiety, time away from home, or other
effects that would be similar to those produced by procedures that they have
experienced” (Institute of Medicine 2004). The goal is to make the research
procedures tangible for the child and parents, thereby improving child assent and
parental permission (CIOMS 2002; Department of Health Education and Welfare
1978b).
In assessing whether an intervention or procedure presents no more than a minor

increase over minimal risk, there must be sufficient data that any research-related
pain, discomfort or stress will not be severe and that any potential harms will be
transient and reversible (Fisher et al. 2007). Even if the average risk associated with
an intervention or procedure is thought to be low, if the risk estimate is unknown,
reflects a large degree of variability, or has not been adequately characterized, then
the risks of an intervention or procedure cannot be considered only a minor increase
over minimal risk.
For example, single-dose pharmacokinetic (PK) studies of cough and cold
medicines in children may qualify as presenting only a “minor increase over
minimal risk,” depending on the associated data. PK studies may be necessary to
establish the correct dose to be used in subsequent efficacy studies. However, the
single-dose of a product is unlikely to offer a direct benefit to the child (unless
symptomatic) and is associated with a small, but higher than minimal risk (based on
prior data). Therefore, to be enrolled, children must have a disorder (symptoms) or a
condition (asymptomatic, but at risk based on empiric criteria). A child may be
considered “asymptomatic, but at risk” using a combination of three criteria:
(frequency) >6 infections per year for children 2 to <6, >4 infections per year
for children aged 6 to <12; (crowding) four or more persons living in a home or
three or more people sleeping in one bedroom; and (exposure) another ill family
member in the home or a child in the family who is attending preschool or school
with six or more children per group (Nelson 2010).
Procedures that may present a minor increase over minimal risk (depending on
the research context, the specific population of children and the skill of the investi-
gator) have included: lumbar puncture, bone marrow aspirate with appropriate
procedural sedation (CIOMS 2002; Institute of Medicine 2004), placement of a
blood-drawing peripheral intravenous line for a limited time period, selected
approaches to procedural sedation (Institute of Medicine 2004) and perhaps limited
radiation exposure (Nelson 2006). The risk of a single-dose PK study depends
on both the approach to blood sampling and on the risks of the drug that is being
administered.
Although FDA regulations include this classification of “minor increase over
minimal risk,” EU pediatric regulations do not include such a category of research.
Instead, EU guidance documents refer to research which offers potential direct
benefits to individual research participants and/or to the group (i.e., children
affected by the same disease, or a disease which shares similar features and for
which the product could be of benefit) (European Parliament and the Council 2001).
European regulations that specify direct benefit to the individual are closely aligned
with US regulations that require direct benefit, discussed in the next section. The
“direct benefit to the group” category allows studies to proceed in Europe that
would be approved in the USA under the “minor increase over minimal risk”
category. Thus, while differences in nomenclature exist, the USA and European
approaches are essentially aligned in practice.
In summary, although the ethical importance of restricting risk exposure in
pediatric studies in the absence of direct benefit to the child is widely appreciated,
implementing associated regulations can be challenging and experts have debated

their interpretation. FDA regulations may allow for assessing minimal risk based on
the participants’ routine experiences, however, there are persuasive ethical
arguments for implementing a uniform standard for minimal risk – drawing on
normal experiences of average, healthy children, tempered by the child’s age, risk
duration, cumulative risks, and reversibility of harm. The risks of daily life can also
factor into (rather than determine) the scrupulous parent’s assessment of minimal
risk. In addition, FDA regulation offers the category of “minor increase over
minimal risk” and, with clarification of key concepts, provides guidance for more
challenging evaluations of risk acceptability when there is no direct benefit to
pediatric participants.
3.3 Interventions or Procedures that Offer the PDB
Children should not be placed at a disadvantage by being enrolled in a clinical trial,

either through exposure to excessive risks or by failing to get necessary health care.
Thus, research guidelines worldwide stipulate that persons who cannot provide
informed consent – including children – should be enrolled in clinical trials only
when the risks are low or the research offers a compensating potential for direct
benefit that is comparable to available alternatives (ICH 1996; CIOMS 2002).
Similarly, FDA regulations permit pediatric research involving an intervention or
procedure that presents more than a minor increase over minimal risk only if it
“holds out the PDB for the individual subject” or “is likely to contribute to the
subject’s well-being.” Such interventions or procedures must meet two conditions
(1) “the risk is justified by the anticipated benefit to the subjects”; and (2) “the
relation of the anticipated benefit to the risk is at least as favorable to the subjects as
that presented by available alternative approaches” (21 CFR 50.52, 2011). Research
that offers a PDB includes several key concepts that require interpretation:
PDB/contribution to well-being, justification of risk, and available alternative
approaches.
3.3.1 PDB/Contribution to Wellbeing
Current regulatory frameworks or national and international clinical research

guidelines do not explicitly define “direct” benefits, and the literature offers varying
views on which benefits are direct. King (2000) provided an influential account of
research-related benefits in which she distinguishes between direct (clinical benefits
arising from receiving the experimental intervention), collateral (arising from other
aspects of the protocol, e.g., medical care), and aspirational (social value of
scientific knowledge) benefits. Direct benefit must accrue to the individual research
participant, and result from the specific research intervention or procedure, not
from ancillary benefits such as health care that may be provided in the trial. The
consequences of an intervention cannot be determined a priori, and thus cannot

serve as the basis for an assessment of direct benefit that Wendler and Miller (2007)
suggest. The determination of the “prospect of direct benefit” is based on the design
of the intervention (i.e., choice of dose, duration, method of administration, and so
forth) given the available evidence, and not the investigator’s state-of-mind or
belief in the therapeutic value. The evidence in support of the PDB is generally
based on mechanistic and in vivo studies of the intervention in animal models or
studies in adult humans.
This account does not squarely address the status of diagnostic or monitoring
procedures that are needed to help answer the scientific questions posed by the
study (e.g., additional scans, blood draws, or biopsies). As noted earlier, an appro-
priate balance of risk and potential benefit is required for each of the interventions
and procedures included in the trial. Monitoring procedures may not per se offer a
PDB, yet may be critical in evaluating the safety of other interventions that do offer
a PDB. More recent accounts of direct benefit have explicitly considered these
procedures (Friedman et al. 2010; Nelson et al. 2010; Miller et al. 2003).
Under current US regulations, there are two ways that the risks of such a
monitoring procedure could be evaluated. If the monitoring procedure is made
necessary by the administration of the investigational product, the risks of the
monitoring procedure may be justified by the PDB of the experimental intervention.
Using this approach, the administration of the investigational product and the
monitoring made necessary by that administration could both be considered under
21 CFR 50.52 (greater than minimal risk with PDB). Alternatively, the monitoring
procedure may be viewed as not offering a PDB, and thus considered under either
21 CFR 50.51 (minimal risk) or 21 CFR 50.53 (minor increase over minimal risk).
In addition, monitoring procedures that may impact on clinical care may offer PDB.
For example, if clinical monitoring of blood levels in order to adjust drug dosing
were necessary, the risks of venipuncture would be justified because the blood
levels obtained in this way may affect clinical management.
3.3.2 Justification of Risk
Whether the risks of an experimental intervention are justified by the potential

direct benefits is a complex evaluation, involving a mix of quantitative and qualita-
tive judgments similar to those made in clinical practice (Department of Health
Education and Welfare 1978b; National Commission 1979; CIOMS 2002). There
should be empirical evidence of sufficient direct benefit [i.e., “scientifically sound”
expectation of success (Department of Health Education and Welfare 1978b)] to
justify exposure to the risks. Consistent with component analysis, the risks of an
intervention or procedure can only be justified by the benefits to be expected from
that same intervention or procedure (Department of Health Education and Welfare
1978b). The justification of risk can include: the possibility of avoiding greater
harm from the disease; the provision of important anticipated benefit to the
individual exposed to risk; the severity of the disease (e.g., degree of disability, life-
threatening); and the availability of alternative treatments.
3.3.3 Available Alternative Approaches
The underlying ethical reason for considering “available alternative approaches” is

the view that a child’s health or welfare should not be placed at a disadvantage by
being enrolled in a clinical investigation (Institute of Medicine 2004). The applica-
tion of this general principle hinges to a large extent on the interpretation of
“available.” Some have argued that the other approaches that need to be taken
into consideration include “any other course of action (or non-action)” (Department
of Health Education and Welfare 1978b). However, the modification of “alterna-
tive” by “available” raises the question whether all alternatives need to be con-
sidered, or only those that are “available” to the subjects to be enrolled in the
clinical investigation (Wendler 2008). In other words, should the range of available
alternatives against which the risks and potential benefits of the experimental
intervention are compared be all those that are “universally” available, or should
the alternatives be limited to those that are “locally” available (Lie et al. 2004;
Macklin 2001; London 2000)?
To help address this question, we turn now to selected ethical issues in the design
and conduct of pediatric clinical trials. The topic of clinical equipoise is followed
by a discussion of the choice of an appropriate control group, including the use of a
placebo control in pediatric clinical trials. The alternative of an actively controlled
trial is explored, with special attention to issues of randomized withdrawal and non-
inferiority (NI) designs in the pediatric population. Finally, we pursue the question
of when to initiate first-in-human (FIH) studies in the pediatric population, followed
by two issues related to the conduct of trials: optimal safety-monitoring practices
and compensation in pediatric research.
4 Selected Ethical Issues in the Design and Conduct

of Pediatric Research
4.1 Clinical Equipoise
Clinical equipoise is commonly defined as “genuine uncertainty on the part of the

expert medical community about the comparative therapeutic merits of each arm of
a clinical trial.” Advocates of clinical equipoise argue that it “provides a clear moral
foundation to the requirement that the health care of subjects not be disadvantaged
by research participation” (Canadian Institutes of Health Research 1998; with 2000,
2002 and 2005 amendments; Medical Research Council 2004).
The concept of equipoise combines two separate principles (Miller and Brody
2007). The first principle is the scientific principle of “uncertainty” (i.e., the null
hypothesis between the investigational product and the comparator or control
group). However, this principle is a requirement of all ethical research, and the
specification and application of this principle of “uncertainty” is complex (Veatch
2007). The uncertainty of the individual clinician is not decisive, but rather the
uncertainty of the relevant community. The morally problematic area is where
sufficient data have been developed such that clinical equipoise is disturbed, but
insufficient data exist to justify a scientific (or policy) conclusion (Veatch 2007;
Gifford 2007).
The second principle contained within the concept of equipoise is the ethical
norm that no one enrolled in a trial should receive an inferior treatment (i.e., known
effective treatment should be provided). Here clinical equipoise is seen as a
specification of the “duty of care” (Miller and Brody 2007). From this perspective,
the dispute about the role of equipoise is primarily about whether the “duty of care”
(carried over from the clinical setting based on the fiduciary duty of a physician to
act in a patient’s best interest) should be the ethical framework for clinical research
(Institute of Medicine 2004). Proponents of equipoise may argue in favor of
actively-controlled comparator trials, as such trials may provide more useful clini-
cal information. However, this approach does not solve the tension between having
enough information to make an “individual patient decision” and enough to “war-
rant making a policy decision” (Gifford 2007).
All parties to the debate over equipoise as a guiding principle of clinical research
accept the need for a demarcation between interventions or procedures that either
offer or do not offer a PDB. The regulations of many countries are grounded on this
distinction. The view that no child should be disadvantaged by participation in a
clinical trial bears some resemblance to clinical equipoise. However, an affirmation
of the child-patient’s right to competent medical care and to protection from undue
risk of harm when participating in a clinical investigation does not require nor entail
the principle of clinical equipoise. The patient-subject’s right to competent medical
care should be operationalized in the structure of the investigational protocol
(London 2007). The nature of the scientific uncertainty to be resolved by the
study design should be specified, and the comparability of alternatives – namely,
the ethical and scientific argument in favor of the chosen control group – should be
justified.
4.2 Choice of Control Group and Placebo Controls
The choice of an appropriate control group for a clinical investigation should be

approached from two perspectives – scientific and ethical. From a scientific per-
spective, what is the appropriate comparator to use in order to demonstrate the
safety and/or efficacy of the intervention? The primary focus is on designing the
clinical investigation so that any uncertainty about the research objective(s) is
resolved. From an ethical perspective, does enrollment in a clinical investigation

place subjects at an unreasonable risk (i.e., one that is not compensated by a
sufficient PDB)? Are individuals enrolled in the clinical investigation not receiving
a treatment that they should otherwise receive as part of competent medical care?
Importantly, the enrollment of a subject in the placebo group does not offer that
subject a PDB. No direct medical benefit will be available from the placebo itself,
and the avoidance of exposure to an unknown risk of the experimental intervention
cannot be considered a direct medical benefit. As noted earlier, direct benefits are
limited to desirable clinical effects arising from receipt of the experimental
intervention.
The ethics of the choice of control group has been the subject of much debate,
focused on either the use of placebo controls or on the choice of a local standard
(which may or may not be a placebo) as the control group. The starting point of this
debate is often the Declaration of Helsinki, which currently states that “a placebo-
controlled trial may be ethically acceptable, even if proven therapy is available,
under the following circumstances (1) where no current proven intervention exists;
or (2) where for compelling and scientifically sound methodological reasons the use
of placebo is necessary to determine the efficacy or safety of an intervention and the
patients who receive placebo or no treatment will not be subject to any risk of
serious or irreversible harm” (World Medical Association 2008). The ICH E-10
Choice of Control Group guidance argues that a placebo-controlled trial may be
ethically justified when there would be “no serious harm” from withholding known
effective treatment (2001). Even if there would be a good scientific reason to
withhold a known effective treatment in order to demonstrate the efficacy of a
new treatment, ICH and CIOMS make it clear that withholding proven therapy
would only be ethically acceptable if the use of placebo would not add any risk of
serious or irreversible harm to the subjects, even if the use of an active comparator
would undermine the ability of the clinical investigation to produce scientifically
sound results (ICH 2001; CIOMS 2002).
Arguably, the clarification of when a placebo control may be used in place of
proven effective treatment remains consistent with clinical equipoise. From this
perspective, a placebo is acceptable when “patients have provided an informed
refusal of standard therapy for a minor condition for which patients commonly
refuse treatment and when withholding such therapy will not lead to undue
suffering or the possibility of irreversible harm of any magnitude” (Canadian
Institutes of Health Research 1998; with 2000, 2002 and 2005 amendments).
However, whether or not subjects would commonly refuse standard therapy for a
minor condition is not relevant to the ethical justification of the use of a placebo in
the absence of “any risk of serious or irreversible harm to the subjects.” The
withholding of a known effective treatment from children enrolled in a clinical
investigation may appear to violate the principle of clinical equipoise. Neverthe-
less, such a violation may be ethically justified if the risk exposure is limited to low
risk (Institute of Medicine 2004). In effect, the risk exposure must be limited to that
same level of risk that would be acceptable for an intervention or procedure that
does not offer a PDB. Thus, the risk related to withholding a known effective
treatment from children enrolled in the placebo arm of a study, for example, must
be limited to no more than a minor increase over minimal risk because the placebo
arm of a study does not offer a PDB.
A variant of the discussion about placebo (or no treatment) controls concerns
the use of “local” versus “universal” standards to determine the appropriate
control group. In other words, should “proven effective therapy” only refer to
treatments that are actually available in the location where the clinical investi-
gation is being conducted? Some argue that the purpose of a clinical investiga-
tion is to alter clinical practice. Thus, “it is crucial. . . to take the study context
into account when designing and conducting such studies.” Simply, the appro-
priate control group (or comparator) should be drawn from actual clinical
practice in that setting (Weijer and Miller 2004). However, others argue that
the withholding of known effective treatment based on the underlying inequities
in the distribution of medical care is unjust and exploits those less fortunate
(Shaddy and Denne 2010). A middle ground in this debate requires that the
proposed study provide valuable and timely information about a health care need
important to the local population, such that there is a reasonable likelihood that
the local population could benefit from the research (World Medical Association
2008).
4.3 Alternatives to Placebo Controlled Trials
If a classical placebo-controlled trial is not ethical or practical, there are several

alternatives that may reduce or eliminate the exposure to placebo. In a rando-
mized withdrawal trial, all eligible patients with a particular disease are initially
treated with the experimental drug. Patients that have a successful initial response
are then randomized in a double-blind fashion to remain on the drug or be
switched to placebo (or lower doses). The primary study endpoint is time to
relapse, usually defined as the duration of time before which clinical signs and/or
symptoms of the disease recur. These designs are useful when a trial of medica-
tion withdrawal or change in therapy may be clinically indicated, particularly if
the experimental drug is similar to those already marketed (Balfour-Lynn et al.
2006). Any child that relapses may immediately be provided with “rescue”
medication to reduce the harm or discomfort to no more than a minor increase
over minimal risk.
If any exposure to placebo is unacceptable, actively controlled trials may be an
alternative. These trials can be designed to test either superiority or non-inferiority
(NI) of the experimental intervention relative to the control. Superiority trials
generally pose few ethical or interpretational difficulties, provided that the dose
of the control product is not artificially low. However, NI designs can pose ethical
dilemmas under certain circumstances and deserve further comment.
Non-inferiority trials are intended to show that the effect of a new treatment is
not worse than that of an active control by more than a specified margin (Snapinn
2000). The design and interpretation of NI trials is not straightforward. For the NI
trial to be valid, one must have historical studies that provide reliable and precise
estimates of the effect of the active control regimen relative to placebo (ICH 2001).
Further, NI trials do not assure that the experimental agent is “at least as effective”
as the active regimen unless superiority of the experimental agent is demonstrated.
An experimental intervention may be inferior to the active control and still demon-
strate non-inferiority.
Therefore, the primary ethical question is whether it is appropriate to use an NI
design for pediatric trials where the inferior performance of the experimental
intervention may be associated with serious morbidity or mortality in children.
For example, suppose a new antibiotic were tested for life-threatening infections.
Even if the experimental drug were shown to be non-inferior, more children may
still be at risk of dying due to inferiority of the experimental drug. The ethical
acceptability of this design depends on a variety of factors. There may be times
when the new treatment offers a potential benefit in lower toxicity or improved
usability that may justify using the new treatment in a given population even if it
were shown to be slightly inferior to standard care. However, the burden of proof
should be on the advocates of the NI study to present convincing evidence that the
benefits of the new product outweigh the potential inferiority such that the trial
should be allowed to proceed.
4.4 Special Concerns in FIH Pediatric Clinical Trials
An FIH trial is a clinical investigation in which a therapeutic intervention, previ-

ously developed and assessed through in vitro or animal testing, or through mathe-
matical modeling, is tested on human subjects for the first time. FIH studies are
heterogeneous in design, ranging from dose escalation studies testing conventional
oncology drugs to gene transfer trials or monoclonal antibodies that target newly
discovered biological pathways. A major ethical question concerning the conduct of
FIH trials is whether or not an FIH experimental intervention offers a PDB to the
enrolled child. Some take the view that such research can offer a PDB, contending
that it should be seen as “therapeutic research” (Ackerman 1995) or arguing for
a “relativistic understanding of prospect of benefit” (Kodish 2003). Others believe
that the objective of FIH is not to produce clinical benefits, and that promoting PDB
to participants fosters a therapeutic misconception (Ross 2006; Sankar 2004; Miller
2000). A middle ground requires the recognition that a key ethical dilemma
concerning FIH trials is not simply about whether or not they offer a PDB, but
whether the PDB is of sufficient likelihood, magnitude, and type to justify the
anticipated risks of the experimental intervention (King 2000). Understanding
PDB as an empirical matter laden with uncertainty places the focus on assessing
the strength of evidence – particularly nonclinical evidence – that provides the
scientific rationale for undertaking an FIH trial. There is no consensus, however, on

the quantity or quality of nonclinical or adult human evidence necessary to justify
a pediatric FIH study.
We propose a “sliding threshold” evidentiary approach, arguing that data
(whether animal or adult human) necessary to establish sufficient PDB to justify
the risks of the experimental intervention varies with the severity of the disease and
the adequacy of alternate treatments. The sliding threshold is hierarchical in
character: evidence about structure (design) is considered weaker than evidence
about function (mechanism of action, e.g., molecular targets, biomarkers, physio-
logic pathways), which in turn is considered weaker than evidence related to a
clinical disease model (surrogate or clinical endpoints). Kimmelman’s principle of
“modest translational distance” similarly tries to establish an evidentiary basis for
PDB in FIH studies through a critical examination of the assumptions linking
nonclinical and clinical models (2009, 2010).
A critical issue in the design of many FIH trials is the question of starting dose.
Currently the estimation of a maximum recommended starting dose (MRSD) in an
FIH study often is based on the “no observed adverse effect level” (NOAEL), as
determined in toxicity studies in relevant animal species. The starting dose for human
intervention is then reduced by a substantial safety margin. While this approach may
be acceptable in adults, using a very low dose in children may eliminate any PDB
from the intervention. Dosing studies in animal models using an appropriate bio-
marker or physiologic endpoint may therefore be particularly important for
establishing a dose in children that is likely to have some biological effect.
4.5 Data and Safety Monitoring in Pediatric Clinical Trials
Data Monitoring Committees (DMC) are advisory to the sponsor, and charged with
conducting periodic reviews of accumulated data from ongoing clinical trials to
assess for substantial evidence of benefit, harm, or futility of collecting additional
data (U.S. Department of Health and Human Services FDA 2006). While all
pediatric clinical trials require careful safety monitoring, they do not uniformly
require a formal DMC. The only mandatory use of a DMC in US regulations is for
research studies in emergency settings in which the informed consent requirement
has been waived [21 CFR 50.24(a)(7)(iv) 2011].
However, a DMC is recommended in additional circumstances: large, multi-
center studies of long duration; strong a priori safety concerns, potential serious
toxicity related to study product use; and populations at elevated risk of death/
serious morbidity or in populations deemed potentially fragile (U.S. Department of
Health and Human Services FDA 2006). Current guidance from the American
Academy of Pediatrics recommends DMCs for all pediatric trials (Shaddy and
Denne 2010). In practice, however, DMCs may not be warranted in trials with
few or well-characterized risks or at early stages of product development when
studies have few participants and are not blinded.
4.6 Compensation for Pediatric Research
Compensation for participation in research is a common practice for research studies

that involve both children and adults. A number of different types of compensation
are used in clinical studies, including material or monetary compensation such as
reimbursement for travel, parking, or inconvenience. The amount paid to study
subjects can vary from site to site as well as study to study, even at the same
institution for similar tasks (Shaddy and Denne 2010). The American Academy of
Pediatrics recommends the giving of gifts instead of money to children as a token of
appreciation after the child has completed (or withdrawn from) the trial (1995). While
this model may be appropriate for younger children, remuneration using a wage
model based on time or effort (e.g., a percentage of trial visits or procedures that have
been completed) may be appropriate for older adolescents (Bagley et al. 2007).
Offering payment in studies that enroll children requires parents, investigators,
and IRBs to weigh the importance of several competing values (Bagley et al. 2007).
Incentive payments may be essential to the recruitment and retention of pediatric
study subjects. The obligation to treat all patients fairly might include compensat-
ing them for their time, effort, and discomfort and for their contribution to the social
good. However, payments to parents for their child’s research participation could
potentially influence parents to decide in favor of participation without regard for
the child’s wishes, because there is no personal risk to them (Shaddy and Denne
2010). Some foreign countries prohibit inducements in pediatric trials, either for the
parents, legal representatives or children (Federal Agency for Medicines and Health
Products (Belgium) 2004). In other instances, parents/legal representatives can only
be compensated for their time and expenses (European Union 2008). These
concerns must be carefully weighed to ensure that pediatric research can continue
without unduly influencing a parent to enroll a child in a research protocol that is
not consistent with the best interests of the individual child (Bagley et al. 2007;
Institute of Medicine 2004). The exposure of children to excessive risk due to undue
influence may be avoided if pediatric trials are designed with an appropriate
balance of risk and potential direct benefit.
We now consider a final protection for children in research: parental permission
and the assent of children. We also explore conditions under which parental
permission may no longer be needed under the applicable law of the jurisdiction
in which research is being conducted.
5 Child Assent and Parental Permission
5.1 The Assent Requirement
The requirement for child assent emerged in a 1978 report by The National
Commission (1978b). William Bartholome defined four fundamental elements of
child assent (1) a developmentally appropriate understanding of the nature of the

condition; (2) disclosure of the nature of the proposed intervention and what it will
involve; (3) an assessment of the child’s understanding of the information provided
and the influences that impact on the child’s evaluation of the situation; and (4) a
solicitation of the child’s expression of willingness to accept the intervention
(Bartholome 1996). Considerable disagreement among experts remains about
many fundamental components of assent, including: the definition of assent, the
age at which investigators should solicit assent from children; who should be
involved in the assent process; how to resolve disputes between children and their
parents; the relationship between assent and consent; the quantity and quality of
information to disclose to children and their families; how much and what informa-
tion children desire and need, the necessity and methods for assessing both
children’s understanding of disclosed information and of the assent process itself;
and what constitutes an effective, practical, and realistically applicable decision-
making model (Unguru et al. 2008; Carroll and Gutmann 2010; National Commis-
sion 1979).
Children must affirmatively agree to participate in research unless the assent
requirement is waived. The absence of dissent does not qualify as assent (21 CFR
50.3(n) 2011). US regulations allow the assent requirement to be waived only when
the research holds out the possibility of direct benefit that is available only in the
research context, or if the child is judged incapable of assent (Department of Health
Education and Welfare 1983). Evaluating the capacity of a child to assent to
research participation presupposes an understanding of what the giving of assent
means. If we expect the child to make an adult-like judgment of the risks and
possible benefits of the research, such a capacity may not develop until mid-
adolescence. However, if a child simply needs to agree based on their own
perspective on the acceptability of the experience (e.g., the pain of having a
blood test), a younger child would be capable of assent. While not specifying the
elements of assent as Bartholome did (1996), The National Commission opined that
children as young as 7 years of age are capable of assent (Department of Health
Education and Welfare 1978b).
The criteria are found in US regulations are similar to those in international
regulations on child assent and participation in research. For example, the EU
Directive 2001/20/EC states that the following conditions must be met for any
pediatric clinical trial: “(a) consent must represent the minor’s presumed will and
may be revoked at any time, without detriment to the minor; (b) the minor has
received information according to its capacity of understanding regarding the trial,
the risks and the benefits; and (c) the explicit wish of a minor who is capable of
forming an opinion and assessing this information to refuse participation or to be
withdrawn from the clinical trial at any time is considered by the investigator”
(European Parliament and the Council 2001). Specific guidance on age
requirements and assent procedures is again not included.
5.2 Parental Permission
Since children are unable to provide informed consent, pediatric research relies on
parental permission to authorize the enrollment of children in research. There is
wide international agreement on this requirement of surrogate (usually parental)
consent. A parent is generally defined as a child’s biological or adoptive parent, and
a guardian is defined as an individual who is authorized under applicable state or
local law to consent on behalf of a child to general medical care. The parental
permission requirement is intended to protect the child from assuming unreasonable
risks (Rossi et al. 2003).
However, the feasibility of obtaining parental permission may be a problem in
certain circumstances. For example, great distances, lack of communication infra-
structure, social dislocation, or high parental mortality (e.g., HIV affected
populations) may serve to make parents unreachable. US regulations governing
Health and Human Services-funded research at (45 CFR 46.408(c) 2011) allow for
a waiver of the requirement for parental or guardian permission if a research ethics
committee determines that the requirement is unreasonable. However, FDA
regulations for the protection of children (21 CFR 50, Subpart D 2011) do not
include this waiver. Thus, for the majority of FDA-regulated research, parental
permission is required for the enrollment of children. The exception from informed
consent allowed under (21 CFR 50.24, 2011) for research conducted in emergency
settings applies to children as well as adults.
5.3 The Definition of a Child
Children are defined in FDA regulations as “persons who have not attained the legal
age for consent to treatments or procedures involved in clinical investigations,
under the applicable law of the jurisdiction in which the clinical investigation
will be conducted” (21 CFR 50.3(o) 2011). In effect, whether or not an individual
subject is considered a child for the purposes of the application of Subpart D
depends on how the age of majority is defined by state law. State law also defines
certain conditions under which a child who is younger than the age of majority may
be considered emancipated (i.e. not under the control of a parent or guardian) and
thus effectively an adult. These conditions generally include marriage, military
service, or a court order, but vary considerably from state to state. FDA regulations
would allow a minor who meets one of these conditions to be considered an adult
for the purposes of research. In addition, state law may allow a minor to consent for
certain interventions and procedures such as treatment for sexually transmitted
diseases and drug abuse. If the clinical investigation involves one of these con-
ditions, a minor may be considered an adult for the purposes of obtaining informed
consent (absent parental permission). Such a determination would be made by the
local research ethics committee in consultation with legal counsel.
International regulations do not define the pediatric population according to the

age of consent to specific interventions or procedures. For instance, both the
European Commission (2008), and ICH E11 (2000) refer to the pediatric population
as birth to 18 years. The policy of using local judicial or legal procedures to either
appoint a guardian or establish that an adolescent is legally able to consent to the
interventions and procedures included in the research is more defensible than
relying on the interpretation of particular permission guidelines by individual
research ethics committees. The use of established, transparent, and fair judicial
procedures to establish the right of an adolescent to consent to research participa-
tion under the applicable laws of the appropriate jurisdiction respects the differing
moral and legal views of local communities while affirming a liberty interest of
parents to raise their children as they see fit (Nelson et al. 2010).
6 Summary
In recognition of the benefits of pediatric research, research ethics has evolved from
a position of excluding children to one of cautious advocacy – acknowledging the
critical role of pediatric research, but accompanied by careful consideration of the
scientific context, evaluation of risks and benefits, and protection to participants.
Many countries have adopted regulations or guidelines to protect children in
research. Typically, this requires a careful analysis of the risk associated with
each intervention and/or procedure, an evaluation of potential benefits, provisions
for child assent, and ensuring adequate parent/guardian permission. The regulatory
agencies overseeing pediatric research need to make a careful ethical assessment
weighing sometimes complex trade-offs so as to protect children’s welfare and
prevent undue risk of harm while generating scientifically valuable information to
answer important questions concerning the health and welfare of children.
References
21 CFR 50, Subpart D. http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?

CFRPart¼50&showFR¼1&subpartNode¼21:1.0.1.1.19.4. Accessed 3 Jan 2011
21 CFR 50.3(k). http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr¼50.3.
Accessed 3 Jan 2011
21 CFR 50.3(n). http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr¼50.3.
Accessed 3 Jan 2011
21 CFR 50.3(o). http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr¼50.3.
Accessed 3 Jan 2011
21 CFR 50.24. http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?fr¼50.24.
Accessed 3 Jan 2011
21 CFR 50.24(a)(7)(iv). http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?
fr¼50.24. Accessed 3 Jan 2011

Accessed 3 Jan 2011
Accessed 3 Jan 2011
Accessed 3 Jan 2011
21 CFR 56.111(a)(1). http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?
21 CFR 56.111(b). http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRSearch.cfm?
21 CFR Part 50. http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/CFRsearch.cfm?
CFRPart¼50. Accessed 3 Jan 2011
21 CFR Part 56. http://www.accessdata.fda.gov/scripts/cdrh/cfdocs/cfcfr/cfrsearch.cfm?
cfrpart¼56. Accessed 3 Jan 2011
45 CFR 46.408(c). http://www.hhs.gov/ohrp/humansubjects/guidance/45cfr46.htm#46.408.
Accessed 3 Jan 2011
Ackerman TF (1995) Phase I pediatric oncology trials. J Pediatr Oncol Nurs 12(3):143–145
Ad hoc group for the development of implementing guidelines for Directive 2001/20/EC (2008)
Ethical considerations for clinical trials on medicinal products with the paediatric population.
Ad hoc group for the development of implementing guidelines for Directive 2001/20/
EC relating to good clinical practice in the conduct of clinical trials on medicinal products
for human use. http://ec.europa.eu/health/files/eudralex/vol-10/ethical_considerations_en.pdf.
Accessed 10 Dec 2010
American Academy of Pediatrics (1977) Committee on drugs. Guidelines for the ethical conduct
of studies to evaluate drugs in pediatric populations. Pediatrics 60(1):91–101
American Academy of Pediatrics (1995) Committee on drugs. Guidelines for the ethical conduct
of studies to evaluate drugs in pediatric populations. Pediatrics 95(2):286–294
Bagley SJ, Reynolds WW, Nelson RM (2007) Is a “wage-payment” model for research participa-
tion appropriate for children? Pediatrics 119(1):46–51. doi:10.1542/peds.2006-1813
Balfour-Lynn IM, Lees B, Hall P, Phillips G, Khan M, Flather M, Elborn JS (2006) Multicenter
randomized controlled trial of withdrawal of inhaled corticosteroids in cystic fibrosis. Am
J Respir Crit Care Med 173(12):1356–1362. doi:200511-1808OC [pii] 10.1164/rccm.200511-
1808OC
Bartholome W (1996) Ethical issues in pediatric research. In: Vanderpool HY (ed) The ethics of
research involving human subjects. University Publishing Group, Fredrick, MD
Canadian Institutes of Health Research (1998; with 2000, 2002 and 2005 amendments) Tri-council
policy statement: ethical conduct for research involving humans. Canadian Institutes of Health
Research – Natural Sciences and Engineering Research Council of Canada and Social Sciences
and Humanities Research Council of Canada. http://www.pre.ethics.gc.ca/english/
policystatement/introduction.cfm. Accessed 10 Dec 2010
Carroll TW, Gutmann MP (2010) The limits of autonomy: the Belmont report and the history of
childhood. J Hist Med Allied Sci 60(1):82–115. doi:10.1093/jhmas/jrq021
CIOMS (2002) International ethical guidelines for biomedical research involving human subjects.
Council for International Organizations of Medical Sciences (CIOMS) in collaboration with
the World Health Organization (WHO). http://www.cioms.ch/publications/layout_guide2002.
pdf. Accessed 10 Dec 2010
Department of Health Education and Welfare (1973) Protection of human subjects: policies and
procedures. Fed Regist 38(221):31738–31749
Department of Health Education and Welfare (1978a) Notice of proposed rule-making: subpart
D – additional protections for children. Fed Regist 43:31785
Department of Health Education and Welfare (1978b) Research involving children: report
and recommendations of the national commission for the protection of human subjects of bio-
medical and behavioral research. Fed Regist 43(9):2083–2114
Department of Health Education and Welfare (1979) Protection of human subjects; proposed
establishment of regulations. Fed Regist 44(80):24106–24111
Department of Health Education and Welfare (1983) Subpart D: additional protections for children
involved as subjects in research. Fed Regist 48:9818–9820
European Parliament and the Council (2001) Directive 2001/20/EC of the European Parliament
and the Council on the approximation of the laws, regulations, and administrative provisions of
the Member States relating to the implementation of good clinical practice in the conduct of
clinical trials on medicinal products for human use. Off J Eur Commun 121:34
European Union (2008) Ethical considerations for clinical trials on medicinal products conducted
with the paediatric population. Eur J Health Law 15(2):223–250
Federal Agency for Medicines and Health Products (Belgium) (2004) Law of May 7th 2004: unof-
ficial consolidated version. http://www.fagg-afmps.be/en/human_use/medicines/Medicines/
research_development/clinical_trials/index.jsp. Accessed 10 Dec 2010
Fisher CB, Kornetsky SZ, Prentice ED (2007) Determining risk in pediatric research with no
prospect of direct benefit: time for a national consensus on the interpretation of federal
regulations. Am J Bioeth 7(3):5–10. doi:10.1080/15265160601171572
Food and Drug Administration (2001) Additional safeguards for children in clinical research. Fed
Regist 66(79):20589–20600
Food and Drug Administration (2007) Food and Drug Administration Amendments Act of 2007 –
Pediatric Research Equity Act (reauthorization), 110th Congress ed: H.R. 3580, Public Law
110-85
Food and Drug Administration Amendments Act of 2007. Title VI: Pediatric Research Equity Act
of 2007. Pub. L. no. 110-85, 121 Stat 823 (2007)
Fost N (1998) Ethical dilemmas in medical innovation and research: distinguishing experimenta-
tion from practice. Semin Perinatol 22(3):223–232
Friedman A, Robbins E, Wendler D (2010) Which benefits of research participation count as
‘Direct’? Bioethics. doi:BIOT1825 [pii] 10.1111/j.1467-8519.2010.01825.x
Gifford F (2007) So-called “clinical equipoise” and the argument from design. J Med Philos
32(2):135–150. doi:777158743 [pii] 10.1080/03605310701255743
ICH (1996) International Conference on Harmonisation E6(R1): guideline for good clinical
practice. http://www.ich.org/LOB/media/MEDIA482.pdf. Accessed 10 Dec 2010
ICH (2000) International Conference on Harmonisation Guidance on E11 clinical investigation of
medicinal products in the pediatric population. Available via HSR. http://www.fda.gov/
downloads/RegulatoryInformation/Guidances/ucm129477.pdf. Accessed 10 Dec 2010
ICH (2001) International Conference on Harmonisation E10: choice of control group and related
issues in clinical trials available via HSR. http://www.fda.gov/RegulatoryInformation/
Guidances/ucm125802.htm. Accessed 10 Dec 2010
Institute of Medicine (2004) IOM committee on clinical research involving children: ethical
conduct of clinical research involving children. National Academies Press, Washington, DC,
2010/07/30 edn
Kimmelman J (2009) Ethics of cancer gene transfer clinical research. Methods Mol Biol
542:423–445
Kimmelman J (2010) Gene transfer and the ethics of first-in-human research: lost in translation, 1st
edn. Cambridge University Press, Cambridge, UK
King NM (2000) Defining and describing benefit appropriately in clinical trials. J Law Med Ethics
28(4):332–343
Kipnis K (2003) Seven vulnerabilities in the pediatric research subject. Theor Med Bioeth
24(2):107–120
Kodish E (2003) Pediatric ethics and early-phase childhood cancer research: conflicted goals and
the prospect of benefit. Account Res 10(1):17–25
Kopelman LM (2000) Children as research subjects: a dilemma. J Med Philos 25(6):745–764
Lie RK, Emanuel E, Grady C, Wendler D (2004) The standard of care debate: the Declaration of
Helsinki versus the international consensus opinion. J Med Ethics 30(2):190–193
London AJ (2000) The ambiguity and the exigency: clarifying ‘standard of care’ arguments in
international research. J Med Philos 25(4):379–397
London AJ (2007) Two dogmas of research ethics and the integrative approach to human-subjects
research. J Med Philos 32(2):99–116. doi:10.1080/03605310701255727
Macklin R (2001) After Helsinki: unresolved issues in international research. Kennedy Inst Ethics
J 11(1):17–36
Medical Research Council (2004) Medical research involving children. Medical Research Coun-
cil, London
Miller FG, Brody H (2007) Clinical equipoise and the incoherence of research ethics. J Med Philos
32(2):151–165. doi:777158978 [pii] 10.1080/03605310701255750
Miller FG, Wendler D, Wilfond B (2003) When do the federal regulations allow placebo-
controlled trials in children? J Pediatr 142(2):102–107. doi:S0022-3476(02)40245-4 [pii]
10.1067/mpd.2003.43
Miller M (2000) Phase I cancer trials. A collusion of misunderstanding. Hastings Cent Rep
30(4):34–43
National Commission (1979) The Belmont Report: ethical principles and guidelines for the
protection of human subjects of research from the National Commission for the Protection of
Human Subjects of Biomedical and Behavioral Research. National Commission, Washington,
DC
Nelson R (2006) Issues in the Institutional Review Board Review of PET scan protocols. In:
Charron M (ed) Practical pediatric PET imaging. Springer, New York
Nelson RM (2007) Minimal risk, yet again. J Pediatr 150(6):570–572. doi:10.1016/j.
jpeds.2007.03.040
Nelson RM (2010) The scientific and ethical path forward in pediatric product development.
http://www.bioethics.nih.gov/hsrc/slides/Nelson%20-%20NIH%20HSP%20Course%2010-
20-2010.pdf. Accessed 10 Dec 2010
Nelson RM, Lewis LL, Struble K, Wood SF (2010) Ethical and regulatory considerations for the
inclusion of adolescents in HIV biomedical prevention research. J Acquir Immune Defic Syndr
54(Suppl 1):S18–S24. doi:10.1097/QAI.0b013e3181e2012e
Nelson RM, Ross LF (2005) In defense of a single standard of research risk for all children.
J Pediatr 147(5):565–566. doi:10.1016/j.jpeds.2005.08.051
Office for Human Research Protections (2005) Appendix B: Secretary’s Advisory Committee on
Human Research Protections (SACHRP) – Chair Letter to HHS Secretary Regarding
Recommendations. http://www.hhs.gov/ohrp/sachrp/sachrpltrtohhssecApdB.html. Accessed
10 Dec 2010
Ross L (2006) Phase I research and the meaning of direct benefit. J Pediatr 149(1 Suppl):S20–S24.
doi:S0022-3476(06)00372-6 [pii] 10.1016/j.jpeds.2006.04.046
Rossi WC, Reynolds W, Nelson RM (2003) Child assent and parental permission in pediatric
research. Theor Med Bioeth 24(2):131–148
Sankar P (2004) Communication and miscommunication in informed consent to research. Med
Anthropol Q 18(4):429–446
Shaddy RE, Denne SC (2010) Clinical report – guidelines for the ethical conduct of studies to
evaluate drugs in pediatric populations. Pediatrics 125(4):850–860. doi:peds.2010-0082 [pii]
10.1542/peds.2010-0082
Shah S, Whittle A, Wilfond B, Gensler G, Wendler D (2004) How do institutional review boards
apply the federal risk and benefit standards for pediatric research? JAMA 291(4):476–482.
doi:10.1001/jama.291.4.476
Snapinn SM (2000) Noninferiority trials. Curr Control Trials Cardiovasc Med 1(1):19–21
U.S. Department of Health and Human Services FDA (2006) Guidance for clinical trial sponsors:
establishment and operation of clinical trial data monitoring committees. http://www.fda.gov/
downloads/RegulatoryInformation/Guidances/ucm127073.pdf. Accessed 10 Dec 2010
Unguru Y, Coppes MJ, Kamani N (2008) Rethinking pediatric assent: from requirement to ideal.
Pediatr Clin North Am 55(1):211–222. doi:10.1016/j.pcl.2007.10.016, xii
Veatch RM (2007) The irrelevance of equipoise. J Med Philos 32(2):167–183. doi:777159077

[pii] 10.1080/03605310701255776
Weijer C, Miller PB (2004) When are research risks reasonable in relation to anticipated benefits?
Nat Med 10(6):570–573. doi:10.1038/nm0604-570
Wendler D (2008) Is it possible to protect pediatric research subjects without blocking appro-
priate research? J Pediatr 152(4):467–470. doi:S0022-3476(07)00887-6 [pii] 10.1016/j.jpeds.
2007.09.027
Wendler D (2009) Minimal risk in pediatric research as a function of age. Arch Pediatr Adolesc
Med 163(2):115–118. doi:10.1001/archpediatrics.2008.524
Wendler D, Glantz L (2007) A standard for assessing the risks of pediatric research: pro and con.
J Pediatr 150(6):579–582. doi:10.1016/j.jpeds.2007.02.018
Wendler D, Miller FG (2007) Assessing research risks systematically: the net risks test. J Med
Ethics 33(8):481–486. doi:10.1136/jme.2005.014043
World Medical Association (2008) Declaration of Helsinki – ethical principles for medical
research involving human subjects. http://www.wma.net/en/30publications/10policies/b3/
index.html. Accessed 10 Dec 2010
Pediatric Regulatory Initiatives
Steven Hirschfeld and Agnes Saint-Raymond
Contents
1 Regulatory Part 1: United States Federal Pediatric Initiatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
1.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 246
1.2 Brief Regulatory History . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 247
1.3 Early Efforts to Address Pediatric Therapeutics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 248
1.4 First Generation of Coordinated Federal Pediatric Initiatives . . . . . . . . . . . . . . . . . . . . . 249
1.5 Second Generation of Pediatric Initiatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 251
1.6 Use of Extrapolation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 253
1.7 Comparison and Interaction of the Pediatric Regulatory Initiatives . . . . . . . . . . . . . . . 254
1.8 Extension of Human Research Subject Protections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
1.9 Interim Results of the Pediatric Regulatory Initiatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 255
1.10 Third Generation of Pediatric Initiatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 256
1.11 International Harmonization and Other Trends . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 257
2 Regulatory Part 2: The European Regulation and Pediatric Medicines . . . . . . . . . . . . . . . . . . . 258
2.1 European Legislation and Pharmaceutical Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 259
2.2 The European Pediatric Regulation: A Concise History . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
2.3 Major Aspects of the Pediatric Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 261
2.4 The Paediatric Committee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
2.5 The Paediatric Investigation Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 262
2.6 Waivers and Deferrals of the Pediatric Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 263
2.7 Characteristics of the European Pediatric Initiative . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
2.8 Further Research on Pediatric Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 264
2.9 International Collaboration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
2.10 Rewards and Incentives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 265
2.11 Transparency Measures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
2.12 Pharmacovigilance and Long-Term Safety Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . 266
S. Hirschfeld (*)
National Children’s Study Eunice Kennedy Shriver, National Institute of Child Health and Human
Development, 31 Center Drive, Room 2A03, MSC 2425, Bethesda, MD 20892, USA
e-mail: hirschfs@mail.nih.gov
A. Saint-Raymond
Scientific Advice, Paediatrics, and Orphan Drug Sector, European Medicines Agency, 7 Westferry
Circus, Canary Wharf, London E14 4HB, United Kingdom

246 S. Hirschfeld and A. Saint-Raymond
2.13 The Network of Pediatric Research . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267

2.14 Priority for and Funding of Pediatric Development of Off-Patent Medicines . . . . 267
2.15 Survey of all Pediatric Uses of Medicines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
2.16 Reporting on benefits and infringements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 267
2.17 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 268
Abstract A series of government actions have evolved since the 1990s to facilitate
the development of medicinal products for pediatric use using a combination of
incentives and mandates. The initiatives have been successful in stimulating activity
and interest in products developed for pediatric use. The initiatives continue to evolve
as experience accumulates and regulatory agencies develop robust cooperative
programs. A multidimensional program is necessary to achieve the necessary goal
of aligning pediatric therapeutics with adult therapeutics and providing children the
most favorable opportunity to benefit and minimize risk to vulnerable populations.
Keywords Pediatric medicines • Therapeutic orphans • ICH E11 guidelines •

United States Federal Pediatric Initiatives • European Pediatric Regulation •
Written request • Pediatric rules • Pediatric investigation plan • Waivers • Deferrals
1 Regulatory Part 1: United States Federal Pediatric Initiatives
1.1 Introduction
A quotation from Vice President Hubert Humphrey, who trained as a pharmacist, is

inscribed in wall of the lobby of the building named after him in Washington, DC,
which is the headquarters of the United States Department of Health and Human
Services. The inscription reads “The moral test of a government is how it treats
those who are at the dawn of life, the children; those who are in the twilight of life,
the aged; and those who are in the shadow of life, the sick, the needy, and the
handicapped (1976).”
Protections for animals have existed since the nineteenth century, but legal
protections and rights for human children have been a twentieth century develop-
ment. The early part of the twentieth century saw the emergence of specialists in the
diseases of children and the establishment of professional societies.
The United States is governed by a federal system where each of the individual
states govern, regulate, and license commerce and other services within their own
border, and a federal government governs and regulates commerce only between
states and establishes national standards. The foundation of United States law is the
Constitution and its amendments. The Federal government has three branches – one
to generate law (Legislative Branch with two houses of Congress), one to enact and
enforce law (Executive Branch with the President and the Departments and
agencies), and one to judge the law based on the principles in the Constitution
(Judicial Branch or the Supreme Court). When a law is passed by both Houses of
Pediatric Regulatory Initiatives 247
the Congress and signed by the President, it becomes effective. The term “Law” is
synonymous with the term “Act.” Once a law is in effect it becomes part of the
United States Code. The Executive Branch has the authority to issue Regulations
(or Rules) to further clarify the law. Regulations are not voted on but are vetted for
public comment before they become finalized. A Final Rule or Regulation is
published in the Code of Federal Regulations. Regulations are enforceable, but
can be challenged in a Federal court.
1.2 Brief Regulatory History
The general regulation of biologics and medicines in the United States began in the
early twentieth century with a series of laws triggered by several widely publicized
events involving the administration of tainted products causing the deaths of
children. The establishment of laws to regulate the medicinal products began in
1902 when the use of an equine tetanus antitoxin that was not properly purified and
resulted in fatalities among those who received it was widely circulated as a news
story. The United States Congress passed the Biologics Control Act in 1902 to
regulate the purity and safety of serums, vaccines, and other biologics. In 1906,
deaths among infants given a colic syrup containing morphine contributed to the
passage of the Food and Drug Act that required the ingredients of products to be
listed. The authority of the federal government to regulate interstate commerce for
medicinal products was challenged in the courts and upheld in 1912. A subsequent
amendment to the Food and Drug Act known as the Sherley Amendment confirmed
the federal government’s authority.
Over 100 deaths due to a preparation of the antibiotic sulfanilamide containing
diethylene glycol in 1937 triggered debate that led to the Food Drug and Cosmetic
Act of 1938, establishing a legal requirement to demonstrate safety of regulated
medicinal products prior to marketing. The law was amended in 1962 following
deaths and malformations associated with the use of thalidomide to include a
requirement for establishing effectiveness through investigations. Subsequent
regulations clarified the intent to state that the investigations must be adequate
and controlled studies with descriptions of the characteristics of such studies.
The last major principle to be enacted into law was the authority of the federal
government to grant incentives for certain classes of products through the Orphan
Drug Act of 1983. Support for the law came from reports of children with rare
diseases unable to find any available therapy in the United States and traveling to
other countries to seek treatment.
Due to different legal definitions for different types of products, the Food and
Drug Administration (FDA) operates under the authority of many laws and
regulations. Administratively the FDA is organized into different centers based
on the type of product. For example, the Center for Biologics Evaluation and
Research, the Center for Devices and Radiological Health, and the Center for
Drug Evaluation and Research each operate under and apply different sets of
laws and regulations, and other FDA Centers each have their own specific legal
framework and responsibilities. The entire agency is under the direction of a

Commissioner. A license for marketing authorization for the use of product that
is classified as a drug is termed a New Drug Application (NDA) and the
corresponding license for a product classified as a biological is a Biologics License
Application (BLA).
Research programs directed to children began to emerge following World
War II, particularly in the field of pediatric leukemia but also to study infectious
diseases, effects of radiation, and nutrition. While some studies were initiated and
supported by the federal government, others were not. Public media reports and the
academic medical literature began to describe inconsistencies and harm to
participants, particularly children, in research studies. Consequently, a National
Commission was established by the United States Congress through the National
Research Act of 1974 to examine human research practices and make
recommendations. The general principles, as summarized in the Belmont Report
published in 1979, are that research should be conducted with respect for person,
beneficence, and justice. Regulations to protect research participants were
published in the late 1970s. The legal inability of children to formally consent to
participate in research and recognition of the need for specific oversight resulted in
an additional section of the regulations, Title 45 Code of Federal Regulations, Part
46 Subpart D, published in 1983, that specifically outlines the expectation and
responsibilities for research enrolling children. The regulations apply to research
that is funded by the U.S. federal government. The regulations were revised for
consistency and adopted by a total of 16 federal agencies in 1991.
1.3 Early Efforts to Address Pediatric Therapeutics
The term “therapeutic orphan” was invented in 1968 to describe the status of sick
children who lacked appropriate medications. The American Academy of Pediat-
rics published a White Paper in 1974 outlining expectations for research enrolling
infants and children. Concurrently awareness of the need for adequate information
to treat children with medicinal products led to several analyses of product package
inserts of FDA-approved products that showed 78% had no information pertaining
to pediatric use other than, in some cases, a disclaimer that the product is not for use
in children.
The FDA began to specifically address the needs of children with a regulation
establishing a Pediatric Use section for the product package insert, also known as
the product label, in 1979. The FDA subsequently encouraged voluntary develop-
ment of products for pediatric use through the potential use of extrapolation of
adult efficacy under certain conditions in a regulation known as the Pediatric Rule
of 1994. The result of the initiative, despite a new regulation and FDA staff
writing hundreds of letters to companies and promoting the opportunity, was
that the most common response was a statement that a product is not intended
for use in children.
1.4 First Generation of Coordinated Federal Pediatric Initiatives
The enactment of the Prescription Drug User’s Fee Act of 1992 provided the FDA
with additional resources and the Food and Drug Administration Modernization
Act of 1997 (FDAMA) followed with FDA review performance standards and a
section (Section 111) that introduced an incentive for pediatric use of medicinal
products. The principle of providing an incentive that first appeared in the Orphan
Drug Act was now extended not just to products intended to treat diseases or
conditions that met the definition of a rare disease, but to most medicinal products
classified as drugs, with a few exceptions, independent of intended use. Biologics
and some antibiotics were not included in the program. The intent was to enhance a
voluntary program with a financial incentive.
The specific incentive was a 6-month extension of patent life or marketing
exclusivity for all indications, doses, and dosage forms of a product from a sponsor
that use the same chemical moiety as its active ingredient. A patent in the United
States is issued by the Patent and Trademark Office of the Department of Commerce
to protect intellectual property. Marketing exclusivity is a license granted by the FDA
in the form of an NDA to provide product innovators with a period of time without
competition in the market place to sell a product for its claimed use. The initial
standard exclusivity period is 5 years and exclusivity for Supplements (known in
other regions of the world as Variations) is for 3 years. A product approved for an
orphan indication receives 7 years of exclusivity. The result of receiving a 6-month
exclusivity extension for a product was 5½ years of exclusivity for a new product,
3½ years for a Supplement, and 7½ years for a product with orphan designation.
When marketing exclusivity expires, other manufacturers may sell a similar
product if they either have intellectual property rights under license from an active
patent holder or the patent has expired, in which case no license is required. The
new manufacturer must make the product within legal specifications as determined
by federal regulations and register the product through an Abbreviated New Drug
Applications (ANDA) with the FDA in order to market it. A 6-month extension
blocks other manufacturers from entering the market place until the extension
expires. The general expectation is that when marketing exclusivity expires, the
price of a product will decrease due to competition from other manufacturers. The
potential economic impact of a delay caused by an exclusivity extension on the US
health care system costs as well as the potential economic benefit to a product
innovator was considered in the selection of the 6-month time frame.
The incentive process is initiated by a formal pediatric Written Request from the
FDA. The rationale for requiring a pediatric Written Request from the FDA to
perform studies that could qualify for an incentive was to ensure that the studies
were of sufficient quality, design and public health need to justify the potential risks
to children, and avoid the perception of exploitation of a vulnerable population for
financial gain.
The specific model was that the FDA would issue a Written Request to the
product sponsor stating a general framework for the type of pediatric information
expected and an outline of the types of studies, both nonclinical and clinical, to be
performed and a due date. The types of studies could include dose finding studies in
various pediatric populations, safety studies, pharmacokinetic, or pharmacody-
namic studies in various pediatric populations, or a demonstration of clinical
benefit. The specific diseases or conditions and the relevant pediatric populations
were independent of whatever use the product may have for adults and determined
by the public health needs. The due date was determined by a reasonable estimate of
the time and resources needed to generate the requested information and was not
influenced by expiration dates for a marketing license or patent.
The deliverable from a pediatric Written Request was a report describing how
the sponsor responded to the terms of the Written Request by the due date.
A sponsor or a third party could send to the FDA a Proposed Pediatric Study
Request outlining a proposal. The FDA then had the option to utilize or modify the
proposal in developing a formal Written Request. The FDA also had the option to
issue a Written Request without an external proposal.
Proposed Pediatric Study Requests and the study reports in response to a
pediatric Written Request were reviewed in the various review divisions within
the Center for Drug Evaluation and Research to provide the most specific subject
matter expertise. The review divisions would then submit the draft Written
Requests to a centralized multidisciplinary Pediatric Implementation Team to
provide consistency and additional expertise. Following secondary review and
discussion by the Pediatric Implementation Team, the Written Request would be
issued by the appropriate FDA Office Director.
The study reports in response to a Written Request were submitted to the issuing
FDA review division for initial review. Subsequently, the review division would
present a summary and recommendations as to the adequacy of the response to a
multidisciplinary Pediatric Exclusivity Board. The adequacy of the response was
evaluated on the basis of the data quality, information content, and adequacy to
inform pediatric use. It was not based on whether the requested studies
demonstrated efficacy or suggested effectiveness in children. The major principle
was to obtain high-quality information to guide pediatric use, regardless of the
potential for clinical benefit. The knowledge that a product is not effective in a
particular population has value in avoiding risk and unnecessary exposure. The
Pediatric Exclusivity Board then made a determination that was subsequently
communicated to the sponsor. The establishment of the Pediatric Implementation
Team and the Pediatric Review Board provided a uniform framework for pediatric
needs and product assessment.
The entire pediatric incentive program was developed on a time-limited basis of
5 years after inception and scheduled to expire in the year 2002. The rationale was
that if the program were successful, it could be renewed and even improved, and if
it were not successful, other approaches would have to be developed.
In 1998, the FDA published a regulation known as the Pediatric Rule of 1998
that was intended to be a mandate to complement the incentive program in the
FDAMA. The Pediatric Rule targeted products where the disease or condition that
the product was intended to be used for in adults also existed in a pediatric
population. All products with a new active ingredient, new indication, new dosage
form, new dosing regimen, or new route of administration that were likely to be
used in children either due to their potential meaningful therapeutic benefit that
would be considered an advance over currently existing therapy in a limited
population or the product had the potential for widespread use in the pediatric
population were included. Widespread use was calculated use by greater than
50,000 children using the assumption that the threshold for an orphan indication
was a prevalence of less than 200,000 in the United States and that children are
about one quarter of the population; therefore, an adjusted threshold could be used.
In contrast to the incentive program that only applied to medicinal drugs, the
mandate program applied to both drugs and biologics. It did not, however, apply
to products with orphan designation for the orphan indication. The contemplated
penalty for noncompliance was that a product could be considered to be
misbranded, meaning that the product had a use that was intended but not included
in the language of the product package insert or label. A product that is misbranded
can be subject to injunction (legal blockage of production or distribution) and
product seizure.
The 1998 Pediatric Rule had provisions for waivers of the requirement for some
or all pediatric subpopulations on the basis that the disease or condition did not exist
in children or that pediatric studies would not be practical. In addition, sponsors
could request a deferral for compliance so that licensing and marketing a product
for adult use would not be compromised if the pediatric data were not yet available.
Waivers and deferrals had to be requested from the FDA, and deferrals would be
granted with a due date for when the pediatric data would be submitted for review to
the FDA. A full waiver referred to all children and a partial waiver would refer to
only a pediatric subpopulation, usually defined on the basis of age.
The incentive program and the mandate were intended as complementary
regulatory tools in a comprehensive program to advance the need for adequate
information to manage the risks and provide the benefits that medicinal products
can provide to children. As early as 1998, discussions on the pediatric initiatives
between the FDA and other regulatory authorities began, built partially on the
successful experience of developing orphan drug programs in other regions based
on the experience of the US Orphan Product program. In December 2000 under the
French presidency of the European Union, with the FDA consulting on the prepa-
ration of documents, the European Council of Health Ministers adopted a resolution
requesting the European Commission to develop a program for pediatric therapeu-
tics. Further details and elaboration are given in the next section on the European
Regulation.
1.5 Second Generation of Pediatric Initiatives
The initial experience with the FDAMA incentive program was favorable, so in
January 2002, the pediatric incentive program was renewed for another 5 years
when the Best Pharmaceuticals for Children Act (BPCA) became law and included
some new provisions including the study of off-patent medications in partnership
with the National Institutes of Health (NIH), establishment of pediatric specific
FDA advisory committees, enhanced safety reviews, and publication of FDA
clinical and pharmacology reviews on the FDA Web site.
The 1998 Pediatric Rule was challenged in court under the premise that if a
sponsor did not intend to market a product for a particular use, the federal govern-
ment lacked authority to force a sponsor to develop a product for an unintended use.
In October 2002, a federal court in Washington, DC, heard the case and ruled
against the 1998 Pediatric Rule partially on the basis that the US Congress did not
intend to give the FDA the authority to compel a manufacturer to study medicinal
products in children. The court opinion was based in part on the recent renewal
of the pediatric incentive program in BPCA using the argument that Congress
had an opportunity to contemplate pediatric therapeutics and chose an incentive
mechanism.
Rather than challenge the court decision, the Department of Health and Human
Services waited until 2003 when the Pediatric Research Equity Act (PREA) became
law and gave the FDA the authority to enforce the development of therapeutic
products for children under the same conditions as in the 1998 Pediatric Rule –
when the disease or condition was similar in adults and children and when the
product was either a meaningful therapeutic advance or would be widely used. As
in the original 1998 Rule, options to request waivers and deferrals were included
and orphan products were excluded.
The PREA required that products develop a Pediatric Assessment and Plan. The
specific language is that all applications (or supplements to an application) submit-
ted under section 505 of the Act (21 U.S.C. 355) or section 351 of the Public Health
Service Act (PHSA) (42 U.S.C. 262) for a new active ingredient, new indication,
new dosage form, new dosing regimen, or new route of administration to contain
a pediatric assessment unless the applicant has obtained a waiver or deferral
(section 505B(a) of the Act). It also authorizes FDA to require holders of approved
NDAs and Biologic Licensing Applications for marketed drugs and biological
products to conduct pediatric studies under certain circumstances (section 505B
(b) of the Act). The PREA applied to all products that received marketing authori-
zation since April 1, 1999, because that was the date the 1998 Pediatric Rule
became effective.
If a product did not meet the criteria for compliance with the need for
pediatric studies, then the Pediatric Assessment and Plan would be to request a
waiver. Nonetheless, the potential use of a product in children must be
contemplated by every sponsor wishing to file a product use claim for marketing
authorization.
Waivers are considered for three general circumstances:
• Studies are not practical due, for example, to the rarity of the disease or condition
in children.
• The product is likely to be unsafe or ineffective in children.
• The product is considered neither a meaningful therapeutic advance nor is likely

to have widespread use.
Generic products that are licensed under ANDA are generally exempt, but
ANDAs submitted under an approved suitability petition under section 505(j)(2)
(C) of the PHSA for changes in dosage form, route of administration, or new active
ingredient in combination products are subject to the pediatric assessment
requirements that PREA imposes. If clinical studies are required under PREA for
a product submitted under an approved suitability petition and a waiver is not
granted, that application is no longer eligible for approval under an ANDA.
PREA requires development of age-appropriate pediatric formulations with a
waiver possible if the applicant can demonstrate that reasonable attempts to pro-
duce a pediatric formulation necessary for that age group have failed.
The off-patent program in partnership between the FDA and the NIH was guided
by a process to determine priorities for products to study based on chemical entities
that were ranked on the basis of discussion at public meetings by subject matter
experts. The results of the prioritization process were published annually in the
Federal Register.
1.6 Use of Extrapolation
The FDA organized a pediatric extrapolation working group that presented a

framework in 2003 for using nonpediatric data in supporting pediatric efficacy. In
order to define the nature of the evidence used to extrapolate adult clinical data to a
pediatric population, applications from 34 drugs in 23 indications that were granted
Pediatric Exclusivity under the 1997 FDAMA were reviewed for the approaches
used to relate diseases or conditions found in both adult and pediatric populations.
Multiple sources of data were used. Clinical indications approved for adults for
each drug were analyzed with respect to pathophysiology, nonclinical data, phar-
macokinetics, exposure–response relationships, clinical signs and symptoms, labo-
ratory and surrogate measures, natural history and response to therapy, and then
compared to the pediatric condition. Components important in determining
relationships between adult and pediatric conditions were identified and classified
into four categories: (1) nonclinical data, (2) pathophysiology, (3) natural history,
or (4) response to therapy. Analysis showed that similarity of pathophysiology was
the most common basis for supporting extrapolation, followed by similar response
to therapy.
An algorithm on the use of extrapolation was published in an FDA Guidance
Document on “Exposure–Response Relationships – Study Design, Data Analysis
and Regulatory Applications” (2003) that outlined the need for pediatric studies
using available data. http://www.fda.gov/downloads/Drugs/GuidanceCompliance
RegulatoryInformation/Guidances/UCM072109.pdf
Pediatric Study Decision Tree

Reasonable to assume (pediatrics vs adults)
similar disease progression?
similar response to intervention?
NO YES TO BOTH
Conduct PK studies Reasonable to assume similar

Conduct safety/efficacy trials* concentration- response (C-R)
in pediatrics and adults?
NO NO YES
Is there a PD measurement** Conduct PK studies to

that can be used to predict achieve levels similar to adults
efficacy? Conduct safety trials
YES
Conduct PK/PD studies to get Conduct safety trials
C-R for PD measurement
Conduct PK studies to achieve
target concentrations based on C-R
The FDA continues to refine the use of extrapolation through a multidisciplinary

extrapolation working team.
1.7 Comparison and Interaction of the Pediatric Regulatory

Initiatives
A comparison of the pediatric mandate and incentive programs is outlined in

Table 1.
With both the incentive and the mandate for pediatric product research in law,
the interaction between the opportunity to qualify for an incentive and the need to
comply with the mandate required clarification. The FDA issued a draft Guidance
Table 1 Comparison of major features of US Pediatric Initiative Programs

US Pediatric Mandate Program (PREA) US Pediatric Incentive Program (BPCA)
Applies to all drugs and biologicals except orphan Biologicals and some drugs excluded but
designation includes orphan designation
Only applies to the drug product and indication Applies to all products with same active
under review moiety
Only applies if an approved or pending indication Eligible indications for study must occur in
occurs in adults and children pediatric populations
Only applies if there is a meaningful therapeutic Only applies when there is underlying patent
advance or widespread use or exclusivity protection
May be used as often as public health need arises May only be used once in a product lifetime
Mandatory – compliance expected Voluntary – no compliance expected
document in 2005 to address the question. A Guidance document is a nonbinding

public statement from a regulatory agency that reflects current thinking and
represents a framework for discussion and interaction.
The FDA Guidance notes that the FDA cannot issue a Written Request for
studies that have already been submitted to the agency. Thus, a sponsor that wishes
to qualify for the incentive must obtain a Written Request under BPCA prior to
submitting studies that are mandated under PREA. Studies performed to address
PREA requirements may not be adequate to address a BPCA Written Request
because the Written Request can have a broader scope. PREA is limited to
conditions where the adult and pediatric diseases are considered similar, while a
Written Request is based on public health needs that could extend to any potential
pediatric use, including diseases or conditions that are not found in adults.
The opportunity for a sponsor to address the mandate and qualify for the
incentive is therefore time limited and context dependent. In addition, the timing
of the receipt of a Written Request and the submission of pediatric study data are
critical. The interaction between the incentive and the mandate when the two are
separate programs under separate laws has been approached by the European
pediatric initiatives in a combined program.
1.8 Extension of Human Research Subject Protections
The US regulations in the Code of Federal Regulations Title 45 Part 46 that pertain
to human research protection developed during the 1970s and 1980s and revised in
the 1990s apply to research that is funded by the federal government. Research not
funded by the federal government but regulated by the FDA is covered under
regulations in Title 21 Part 50. In 1996, the FDA published the International
Conference on Harmonization of Technical Requirements for Registration of
Pharmaceuticals for Human Use (ICH) E6 Guidelines, also known as the Good
Clinical Practice Guidelines as a Guidance Document. In 2000, the FDA published
ICH E11 on Clinical Investigation of Medicinal Products in the Pediatric Popula-
tion as a Guidance Document. Guidance documents, however, are not legally
binding, so in order to provide the same level of protection to children who
participate in nonfederal government funded research as provided to children who
participate in federally funded research, the FDA adapted the provisions in Title 45
Part 46 Subpart D that pertain to children to Title 21 Part 50 in 2003.
1.9 Interim Results of the Pediatric Regulatory Initiatives
The BPCA and the PREA were scheduled to expire in 2007. By the end of March
2007, under the incentive programs in FDAMA and BPCA, the FDA had issued
about 340 Written Requests, granted the incentive for 136 products representing
129 active chemical moieties, and revised 118 product package inserts with new
pediatric information. The total number of submissions for an incentive was 149, so
the favorable determination rate was about 91%. Under the mandate program for
PREA, the FDA revised 55 product package inserts with new pediatric information.
The total for both programs was 173 products with new pediatric information.
Of products that received the incentive, 73 had FDA medical or pharmacology
reviews or both posted on the FDA Web site by March 2007.
An analysis of these reviews showed that there were 195 individual pediatric
studies across 33 drug classes in 12 disease categories. The average number of
studies per product was about 3 with a range from 1 to 9 and the average number of
patients per product was about 360 with a range from 11 to 1,550. The total number
of pediatric patients enrolled for all products was about 25,000.
Studies could be classified into four types – pharmacokinetic only (19%),
pharmacokinetic and pharmacodynamic (17%), pharmacodynamic only (conven-
tionally referred to as proof of concept or Phase 2 studies) (32%), and efficacy
studies (32%). An efficacy study was defined as a study with a clinically relevant
outcome measure and with adequate statistical power to formally establish efficacy.
All studies were considered to varying degrees to be safety studies. About one third
of all studies had a formal pharmacokinetic component, underlying the importance
of dose determination in different pediatric subpopulations. A common theme in
many of the studies was the need for dose adjustments in 3- to 5-year-old children.
1.10 Third Generation of Pediatric Initiatives
The Food and Drug Administration Amendments Act of 2007 (FDAAA) renewed
the BPCA as Title V of FDAAA with some modifications and the PREA for an
additional 5 years. The major modifications in the BPCA are as follows:
• Listing of off-patent drug prioritization process.
• Prioritization of off-patent products to be studied framed by public health needs
based on diseases and conditions rather, as in the prior version of the BPCA,
based on specific products.
• Flexibility in funding mechanisms that the NIH may use for pediatric studies
related to either off-patent drugs or on-patent drugs in the case of the sponsor
declining a Written Request.
• Enhanced program for training in pediatric pharmacology.
• Description of the role and responsibilities of the Pediatric Committee (PeRCO)
at the FDA to review Written Requests, review pediatric study reports, and track
and make public pediatric activity.
The PREA was renewed as Title IV of FDAAA and a new law, Title III – The
Pediatric Medical Device Safety and Improvement Act, was added. The Pediatric
Medical Device Safety and Improvement Act has provisions for:
1. Requirement to perform pediatric studies in relevant populations for medical

devices that are either under development or will be licensed for marketing.
2. Applicability of the law to “patients” who “suffer from” a disease or condition.
3. Definition of a “pediatric patient” as “patients who are 21 years of age or
younger at the time of the diagnosis or treatment.”
4. Specific safety monitoring requirements.
5. Funding of demonstration projects.
6. Development of a federal pediatric medical device plan.
7. Designation of a pediatric medical device point of contact at the NIH.
The demonstration projects for pediatric medical device development have been
funded in 2009 and are under the direction of the FDA Office of Orphan Products
with scientific input from the NIH and consist of a consortium of three university-
based centers in different geographic regions of the United States.
As of mid-2009, about 370 drugs had been issued Written Requests under
the pediatric incentive, about 160 drugs had been granted an incentive based on
pediatric data, and about 160 product package inserts had been changed. The
pediatric mandate resulted in about 80 product package insert changes for a total
of about 240 products with new pediatric information as a result of the pediatric
initiatives.
1.11 International Harmonization and Other Trends
The near term future of the US pediatric initiatives includes the harmonization and
coordination of a fragmented and diverse clinical research infrastructure. The NIH
are supporting several programs designed to augment current clinical research
efforts and transform the culture of research to one of stability, cooperation, and
collaboration. The most comprehensive is the Clinical and Translational Science
Awards Consortium administered by the National Center for Research Resources to
build a national infrastructure for translational and clinical research with a man-
dated pediatric component. Additional programs from other institutes and centers
are coordinating with the Clinical and Translational Science Awards program as
they evolve their own programs.
A major operational principle of all the efforts is the concept of interoperability –
the capacity to integrate technical and scientific functions on multiple levels.
Examples include standards for data acquisition, data transmission and data archiv-
ing, agreement on terminology and harmonization of definitions, and assessments
of outcome measures. The technical and scientific alignment in several domains has
been a priority for the pharmaceutical and biotech industries for over a decade and
is actively supported by and has participation of the FDA.
In the United States, most pediatric patients enrolled in clinical research studies
are referred and evaluated by academic investigators. A series of workshops and
meetings over the last decade have addressed the expectations of commercial
sponsors and regulatory authorities with academic investigators to facilitate the

operations and compliance of pediatric clinical research. As a consequence of the
federal pediatric initiatives, many pharmaceutical companies now have pediatric
investigators and pharmacologists on staff. The interactions between pediatric
investigators in the regulated industry and academic pediatric investigators are a
basis to facilitate pediatric product development.
The FDA has been engaged in formal interactions with international partners for
the past 20 years and with attention to pediatric issues for the past decade.
Structured and scheduled interactions occur monthly between the FDA and the
European Medicines Agency and less frequent, but substantive interactions occur
between other international partners and the FDA and other US agencies.
In combination with the European pediatric initiatives, a culture change has
occurred in medicinal product development that has extended from the heads of
companies to the lecture halls and clinics where specialists are trained to anticipate
and plan for a pediatric component in all development plans.
Co-funding between public and private sources for pediatric projects had its
origins in the Orphan Drug program and became formalized with the BPCA.
Federal funding agencies now work routinely with foundations and other nonprofit
partners as well as commercial partners and have dedicated staff and a legal
framework to function in. As an example, a public–private partnership to develop
biomarkers, The Biomarkers Consortium, has the FDA, the NIH, and other Federal
partners along with academic and industry partners and an expectation to examine
the pediatric implications for each project the Consortium supports. Other examples
of public–private partnerships that involve the FDA are the Critical Path Institute
and the Reagan-Udall Foundation.
Coordination of technical and harmonization efforts at the interface of pediatric
clinical research, medicinal product development, and regulatory practice has
begun with information sharing and future efforts will address resource sharing
along with specific technical standards in terminology, outcome assessments, data
standards, data sharing, registries, and analyses. Related and parallel international
activities to harmonize human research subject protections and ethical and regu-
latory review are also in progress.
The integrated effect of these initiatives will bring the global community into
alignment with the goals and principles described by Hubert Humphrey in 1976.
2 Regulatory Part 2: The European Regulation and Pediatric

Medicines
As presented in the first section of this chapter on US initiatives, European

pediatricians and authorities also identified the lack of appropriate medicines for
children and relevant data. Although most catastrophes with medicines affected
children, they led to changes in regulatory requirements for the development of
medicines intended for adults.
The adoption of legislation took more time in Europe than in the USA. Despite
European publications and active lobbying by pediatricians as early as the 1980s,
the first initiative was in 1997 with the organization of a roundtable by the European
Commission; the need for legislation was identified, but more time elapsed before
the legislative initiative.
In the meantime, Europe with the USA and Japan adopted a guideline on the
development of pediatric medicines through the ICH process. This guideline was a
follower to the 1997 European guideline. This new guideline, named Clinical
Investigations of Medicinal Products in the Pediatric Population, ICH E11, became
effective in 2000 in the European Union (EU).
2.1 European Legislation and Pharmaceutical Regulation
Made of six countries in 1957, the European Union includes an expanding number
of countries. These Member States have over the years signed various successive
Treaties creating a specific supranational environment of free circulation of
citizens, goods, and capital. The Union has progressively accumulated laws to
harmonize the internal market. To date, the EU includes 27 Member States: Austria,
Belgium, Bulgaria, Cyprus, Czech Republic, Estonia, Finland, Denmark, France,
Germany, Greece, Hungary, Ireland, Italy, Latvia, Lithuania, Luxembourg, Malta,
Poland, Portugal, Romania, Slovakia, Slovenia, Spain, Sweden, The Netherlands,
and the UK. Several countries are candidate to accession (Croatia, Former
Yugoslavian Republic of Macedonia, Turkey, and Iceland). Three more countries
from the European Economic Area/European Free Trade Area are associated with
the work of the European Union without having formally joined: Norway,
Liechtenstein, and Iceland (which has now requested accession). They apply the
same regulation of medicinal products and participate in the work of the European
Agency. The EU has currently 23 official languages (not including Norwegian and
Icelandic) among 60 regional or minority languages. All approval decisions
concerning medicines are issued in all official languages.
The European Parliament, representing the people of Europe, in consultation
with the European Council of Ministers, representing governments, usually adopt
European legislation through a co-decision procedure, but a legislative initiative is
under the sole responsibility of the European Commission. Two sets of laws can be
adopted in the European Union: Regulations and Directives. A Regulation is a law
directly applicable to Member States; a Directive is a more flexible framework,
which requires to be transposed into national law in a given timeframe. A Regula-
tion has clearly a different meaning in the USA and in the EU.
Since 1965, the EU issued various Directives regulating the authorization and
pharmacovigilance of medicines (i.e., medicinal products encompassing
biologicals, vaccines, and chemicals), medical devices, and clinical trials. In
1993, a Regulation created a European Medicines Evaluation Agency (EMEA),
since 2004 the European Medicines Agency (EMA), and established a Community
procedure of authorization valid across the EU. In 2004, a codification exercise of

all pharmaceutical legislation consolidated the various texts and took account of
innovation in this area.
Two major laws are framing the regulation of medicinal products in the EU,
Regulation (EC) No 726/2004, which covers the Community procedures and the
Agency, and Directive 2001/83/EC, which covers the marketing authorization of
medicinal products, the content of an application, and “decentralized” (or national)
and referral procedures. Both laws have already been amended several times and
complemented by the Regulation on medicinal products for paediatric use in 20061
(Regulation (EC) No 1901/2006, hereafter the Pediatric Regulation) and the Regu-
lation on Advanced Therapies (Regulation (EC) No 1394/2007).
Additionally, a Directive (2001/20/EC) sets the framework for interventional
clinical trials using medicinal products, and several Directives cover the supervi-
sion of medical devices. The European Medicines Agency is coordinating activities
relating to authorization and supervision of medicinal products in collaboration
with National Medicines Authorities, but both the authorization of clinical trials
and that of medical devices remain activities of national authorities.
The European Commission is the decision-making body for Community
procedures once the Agency has given a positive scientific opinion on the quality,
safety, and efficacy of the product through its Committees. National Authorities
grant authorizations for national marketing authorization procedures only. The
choice of using the Community instead of a national procedure depends on the
nature of the medicine or its intended indication. Biologicals, orphan medicines,
and medicines intended for the treatment of cancer, diabetes, HIV, neurodegenera-
tive diseases, viral diseases, and autoimmune diseases must go through the Com-
munity procedure. The Community procedure is optional for other medicines, but
in practice all new medicines are now using the Community procedure, whereas
many generics use the national procedures. Once authorized, a medicinal product is
protected by 10 years of data protection, during which no generic can be authorized.
Since the implementation of the Regulation on orphan medicinal products in 2000,
designated orphan medicines receive 10 years of market exclusivity protecting not
only against generic competition, but also against similar medicines, therefore
receiving wider protection. In Europe, similar to the Pediatric Exclusivity of the
US BPCA, medicines developed for children can receive 6 months of extension of
the patent [under the form of an extension of the Supplementary Protection Certifi-
cate (SPC)], provided they meet all necessary requirements.
Scientific opinions to support various regulatory activities on medicines are
given by the Scientific Committees of the European Medicines Agency. These
committees include experts from all Member States, and in most Committees also
include patients’ representatives as full members. The Agency has six permanent
Committees, generally referred to by their acronym: the approval Committee
1
Please note that American English spelling is used except where specific terms are referred to, as
British English spelling is generally used in Europe.
(Committee for Medicinal Products for Human Use, CHMP), the Committee for
Orphan Medicinal Products (COMP), the Committee on Advanced Therapies
(CAT), the Committee on Herbal Medicinal Products (HMPC), and the Paediatric
Committee PDCO. The sixth one is a Committee on veterinary medicines (CVMP).
Most Committees have set up and delegated preparatory work (e.g., guidelines) to
expert groups, the Working Parties. One is of particular relevance for the pediatric
development of medicines, the Scientific Advice Working Party, which advises
companies on their proposed development. For orphan and pediatric medicines, the
Agency staff has a direct complementary role in the evaluation. For other proce-
dures, the Agency has only a coordination role, as the evaluation is performed by
experts and regulators working in the Member States and finalized by the relevant
Committee.
Following the receipt of an Agency opinion, the European Commission takes all
administrative decisions (e.g., orphan designation) except on Paediatric Investiga-
tion Plans (PIP), which are signed into Decisions by the Executive Director of the
Agency.
2.2 The European Pediatric Regulation: A Concise History
The French Presidency of the EU of 2000 submitted a memorandum to the European

Council of Ministers on the need for pediatric medicines. As a consequence, the
Council adopted unanimously a resolution urging the Commission to initiate legisla-
tion on medicines for children. Between 2000 and 2004, the European Commission
went through a long exercise of consultation of stakeholders, of drafting proposals,
and analyzing the potential impact of such legislation. The existing US model was
scrutinized to take account of its successes and limitations. In September 2004, a first
draft of a Regulation was submitted to the European Parliament and to the Council.
The Pediatric Regulation was adopted by the end of 2006 (Regulation (EC) 2006)
after two readings and substantial amendments. The most significant amendment
introduced by the Parliament was the transparency of pediatric clinical trials.
The Regulation took effect on 26 January 2007, but some obligations were
deferred; this was intended to give time to the pharmaceutical industry to prepare
to what is a dramatic and sweeping change of the regulatory framework for
medicines, affecting not just Europe. At the difference of the US Acts described
in the first section of this chapter, this legislation does not have a sunset clause, but
the Commission must report on its impact after 6 and 10 years of operation.
2.3 Major Aspects of the Pediatric Regulation
The Pediatric Regulation is extremely complex and affects many other regulatory
procedures. It creates not only rewards or incentives, but also obligations for
pharmaceutical companies developing medicinal products. The development of

medicines for children becomes the rule rather than the exception. An expert
Committee, the PDCO at the Agency, must agree the pediatric development
presented in a PIP, including for national authorization procedures, or when the
medicine was intended for an adult indication only. The Agency Decision on a PIP
is binding for the company, and compliance with its content is necessary for the
submission of applications at Agency or national level. The main other measures of
the Regulation include strengthened measures for pediatric pharmacovigilance,
transparency measures, the creation of a network of pediatric research, and the
funding of off-patent medicines.
2.4 The Paediatric Committee
The PDCO consists of one expert member per Member State, including five
holding simultaneous membership of the approval Committee (CHMP). In addi-
tion, there are three patients’ representatives and three health professionals;
Norway and Iceland are represented (Liechtenstein has no representative). Each
member has an alternate, so currently the full Committee includes 33 members,
plus the 2 Norwegian and Icelandic members, and 35 alternates. The scope of
expertise of the Committee members is defined by the Regulation. The Committee
was established in July 2007 with a Chair elected for 3 years (renewable once). The
Committee meets once a month for 4 days and its main activity is to issue scientific
opinions on PIP and compliance; it can also provide pediatric expertise to the other
Committees of the Agency, or to the Member States.
2.5 The Paediatric Investigation Plan
A PIP or a request for a Waiver must be proposed at an early stage by any company
intending to apply for marketing authorization, i.e., around the end of phase 1 in
adults, and must be agreed by the PDCO. The development must aim at a full
pediatric indication including an age-appropriate formulation and timelines, and
cover all pediatric age groups, i.e., from birth to 17 years inclusive. The least
studied subset of the pediatric population, the neonate, should always be included
in the development where relevant. The scope relates to the potential pediatric use
generally close to the condition developed for adults, or the proposed pediatric
indication when adults are not affected. This is mandatory for new medicines
(biologicals, vaccines, and chemicals are all regulated by the same laws in the
EU), and when the company applies for a new indication, new route of administra-
tion, and/or a new pharmaceutical form for an active substance covered by a SPC or
by a patent, which qualifies for an SPC. The SPC is a European extension of the
patent to compensate for the unusually long development phase of medicinal
products compared to other industrial products; it is variable in length, up to 5 years

maximum.
Orphan medicines must also submit a PIP; however, generics, biosimilars,
traditional herbal, and homeopathic medicines are excluded. Off-patent medicines
can follow a voluntary procedure to be developed according to an agreed PIP, and,
if successful, approved via a specific authorization covering exclusively the
pediatric indication(s), the so-called Paediatric Use Marketing Authorization
(PUMA)
PIPs are submitted to the Agency in electronic format (xml file) and entered
directly into an administrative and scientific database, which will determine and
monitor timelines, generate a number of documents automatically, and allow
tracking the scientific content of applications. The Agency pediatric staff and
two members (or alternates) of the PDCO assess sequentially but independently
the plan over 60 days. The outcome is discussed by the PDCO, which can require
modifications from the company. The PIP assessment is then completed over a
second period of 60 days followed by a month (or less) of decision-making. The
Decision is issued in English and, on request, in the official language of the
applicant. The procedure is free of charge. The PIP Decision specifies the key
elements (e.g., design, end points, and comparator timelines) of each study, trial,
and/or pediatric formulation required by the PDCO. This is close to a Written
Request. However, an agreed PIP or a Waiver is required to validate the
marketing authorization application. A company can apply for Modifications of
an agreed PIP if and when they encounter difficulties to perform the plan, or
there is a change in the state of the art; this procedure takes a maximum of
60 days.
Decisions on PIP or Waivers and Modifications and Opinions on compliance are
available on the Agency pediatric webpage (Decisions on PIP or Waivers 2010).
2.6 Waivers and Deferrals of the Pediatric Development
Similar to the USA, waivers can be obtained where pediatric development is not
necessary, but the legal basis is not identical. In the EU, the pediatric development
can be waived if the disease does not occur in children, if the product is likely to be
unsafe or ineffective in children, and/or if the product does not bring significant
therapeutic benefit, which means that the medicine would not meet an unmet
pediatric need. Development in rare conditions is not waived (unless a study
would not be feasible). In addition, systematic waivers can be issued by the
PDCO to avoid repeated administrative procedures; these are published on the
Agency pediatric webpage and can be referred to without applying to the PDCO
(Class waivers).
Although the PIP must be agreed early, the performance of studies and trials in
children can be deferred until it is safe to do so, consistent with the ICH E11
guideline.
2.7 Characteristics of the European Pediatric Initiative
Main elements of the Regulation

• Paediatric Committee
• Pediatric Development (PIP) or Waiver to be agreed with the Committee
• Applies to all medicinal products (chemicals, vaccines, and biologicals, orphan
medicines)
• Early submission of PIP
• All subsets from birth to 18 years to be covered by PIP
• Waiver of the pediatric development if the condition only occurs in adults, if the
product is likely to be ineffective or unsafe, or if product does not represent
significant therapeutic benefit
• Obligations continue to apply once reward has been obtained
• Reward can be obtained only once
• Transparency of clinical trials
• Transparency of PIP Decisions
• Network of pediatric research networks
• Community funding for priority research into off-patent medicines
2.8 Further Research on Pediatric Development
The PDCO has issued or contributed to several guidelines on drug development,

including one in neonates. Working groups were set up to ensure consistency and to
progress the scientific knowledge on specific aspects of pediatric development such
as pediatric formulations, juvenile animal studies, and the extrapolation of efficacy.
Limiting unnecessary investigations in the vulnerable pediatric population is an
ethical duty, but little is known on how or when extrapolation of efficacy is
legitimate, and, for example, what could be “similar” conditions in adults and
children, or in different pediatric subsets. Gaps in knowledge, once identified by
the PDCO, are discussed with the relevant learned pediatric societies with a view to
stimulating further research.
During the legislative discussion, the European Parliament requested to set up
the ethical framework for the protection of children involved in clinical trials, based
on the legal principles of Directive 2001/20/EC on good clinical practice for
clinical trials. This led to the publication of Ethical Considerations for clinical
trials with the paediatric population.
As pediatric development is complementary to adult development and to avoid
divergences between different Committees, collaboration between the PDCO, the
CHMP, and the Scientific Advice Working Party is ensured. Scientific Advice for
pediatric issues is free of charge at the Agency (in contrast to adult development
requests).
As of December 2009, after less than 2.5 years of operation more than 620
applications for PIP or a Waiver covering more than 960 conditions have been
received by the Agency. The Committee has finalized more than 200 PIP opinions
and the pediatric development has been completed for 14 medicines. The product
information for these medicines is being updated after assessment, and the first
companies can now claim the patent extension.
2.9 International Collaboration
The vast majority of pharmaceutical companies develop medicines at the global

level; it is therefore important to consider not just EU but other regions’
expectations or plans for pediatric development as well. As mentioned in the first
section of this chapter, under the umbrella of the Confidentiality Arrangements (in
place since 2003 between EU and the US), monthly teleconferences are held
between the Agency and the FDA; the Japanese authorities have recently joined
as observers; PIP’s and Written Requests are extensively discussed to understand
any differences and avoid unnecessary duplication. Since August 2007, more than
170 products (on average five per teleconference) and 14 topics of relevance for
pediatric development have been discussed in depth.
Other initiatives are ongoing through the World Health Organization (WHO) to
stimulate pediatric development of medicines (in particular formulations) for other
regions of the world, especially developing and emerging countries. This is partic-
ularly important from the ethical perspective as many pediatric trials will take place
in less developed countries and children should not be used as commodities by
developed countries.
2.10 Rewards and Incentives
In the EU, an extension by 6 months of the SPC (patent extension) can be granted to
a marketing authorization holder who has not only completed the pediatric devel-
opment in conformity with the agreed PIP, but also included all results in the
Product information and obtained a marketing authorization in all Member States
of the EU. The reward can be obtained even when the results show that the product
is unsafe or ineffective in children. It can be obtained only once despite the fact that
several PIPs might still be required.
Provided the same requirements for information and authorization are met,
pediatric development of orphan medicines is rewarded by two supplemental
years of market exclusivity, in addition to the 10 years granted for medicines
intended for rare diseases in the EU.
The voluntary procedure of PUMA attracts incentives of reduced application
fees and 10-year data protection for the pediatric indication and formulation.
2.11 Transparency Measures
The Pediatric Regulation has introduced a number of breakthrough measures giving

clear precedence to public health over commercial (competitive) interests.
PIP Opinions and Decisions are required to be made public; therefore, develop-
ment plans and timelines will be disclosed, which previously were considered
commercially confidential, including for currently unapproved products.
The Pediatric Regulation also requires that any clinical trial or study involving
subjects between birth and 18 years of age be registered into the existing European
database of clinical trials (EudraCT) if at least one investigation site is in the
European Economic Area, or wherever the study takes place if the study is
mentioned in a PIP. The EudraCT database, created in 2004, used to include only
information related to the trial authorization and the database access was limited to
the National Authorities, the Commission, and the Agency. Public access will now
be given to the protocol and to the trial results that have to be submitted within 6 or
12 months of completion. The European Parliament introduced this measure during
the co-decision procedure, on request from pediatric academics and patients’
organizations; this is of high ethical value. The database is currently under modifi-
cation to accommodate this requirement and public access should be implemented
in 2010. In parallel, international collaboration is taking place to ensure conver-
gence of information requirements with clinicaltrials.gov (NIH) and the WHO
portal.
Some existing pediatric study results were never submitted to the European
Authorities. This was all the more obvious when studies included in Written
Requests and submitted to the FDA did not reach European Authorities. To avoid
repeating unnecessarily studies, the Pediatric Regulation mandates companies to
submit all existing pediatric studies completed before the entry into force of the
Regulation and, within 6 months of completion, the results of new pediatric studies
performed with EU-authorized medicines. Existing studies for more than 1,000
active substances, authorized at national level mostly, were submitted and are
undergoing evaluation by National Agencies in a work-sharing exercise. These
studies and their assessments will also be made public through the EudraCT
database.
2.12 Pharmacovigilance and Long-Term Safety Monitoring
In the EU, adverse reactions occurring with medicinal products authorized or

studied in clinical trials must be reported regularly or on an ad hoc basis. In
addition, since 2004, the so-called Risk Management Plans introduce regulatory
measures to prevent and minimize the risks of medicines. These requirements are
strengthened for pediatric medicines and Risk Management Plans are normally part
of submissions for pediatric approval. Long-term safety or efficacy monitoring can
similarly be required by the Agency.
2.13 The Network of Pediatric Research
As the Pediatric Regulation introduces requirements to study medicines in high-

quality ethical research, it also includes provisions to encourage collaboration
between pediatric research centers, investigators, and networks. The Agency is
establishing a network of networks to facilitate the performance of sufficiently
powered studies, to facilitate access to relevant expertise, and to speed up recruit-
ment. This network will also contribute to capacity building in pediatric research.
2.14 Priority for and Funding of Pediatric Development

of Off-Patent Medicines
The Pediatric Regulation provides for specific funding of off-patent medicines

through Community research programs (the Community Framework Programmes,
currently the seventh, spanning 2007–2013) managed by the Commission. To this
effect, a first priority list of about 60 off-patent medicines established in 2004 was
updated and renewed annually since the implementation of the Regulation. The
prioritization was based on public health considerations, using a simple combina-
tion of priority criteria for the conditions to be treated, and for the medicines based
on available data with a view to selecting those likely to be effective and safe in
children. Various learned societies were involved or consulted and the process of
prioritization was efficient. Funding is available each year and twelve projects (e.g.,
morphine in neonates and pediatric oral formulations of methotrexate) have been
funded since 2007. The first results are expected in the next years. This exercise is
now a collaborative effort with the United States National Institutes of Health.
2.15 Survey of all Pediatric Uses of Medicines
As requested by the Regulation and based on data provided by each Member State
on all pediatric uses of medicines, the Agency is preparing a report on pediatric use
of medicines to the European Commission, who will make it available to the public.
This report will contribute to the identification of pediatric needs that the PDCO has
to consider when assessing a PIP.
2.16 Reporting on benefits and infringements
In addition to the impact reports due after 6 and 10 years of operation of the
Pediatric Regulation prepared by the European Commission, the European
Medicines Agency should report every year on companies and products, which
have benefited from incentives and rewards, and on those which fail to comply with
the Regulation. This information will be made public and can be considered as part
of a “naming and praising” or “naming and shaming” process to encourage com-
pliance. Additionally, financial penalties could be imposed by the Commission on
companies failing to comply, but to date the legislation on penalties has not been
updated to take account of pediatric obligations; thus, this possibility remains quite
theoretical.
2.17 Conclusions
Several years after the USA, the European Union adopted a complex law aimed at
improving the available information on medicines for pediatric use through ethical
high-quality research and increasing the overall number of medicines specifically
authorized for children. Through a stringent system of obligations compensated by
economic rewards, a dramatic change in the way medicines are developed is taking
place. This effort is placed under the sign of international collaboration with the
USA and with other regions including developing countries. These new measures
are implemented within an ethical framework to obtain evidence-based information
while protecting the children involved in research.
References
Class waivers. http://www.ema.europa.eu/htms/human/paediatrics/classwaivers.htm. Accessed 11

Jan 2010
Decisions on PIP or Waivers. http://www.ema.europa.eu/htms/human/paediatrics/decisions.htm.
Accessed 11 Jan 2010
European Medicines Agency pediatric webpage http://www.ema.europa.eu/htms/human/paediat-
rics/introduction.htm. Accessed 11 Jan 2010
Network of pediatric research. http://www.ema.europa.eu/htms/human/paediatrics/network.htm.
Paediatric Committee http://www.ema.europa.eu/htms/general/contacts/PDCO/PDCO.html.
Regulation (EC) No 1901/2006 of the European Parliament and of the Council of 12 December
2006 on medicinal products for paediatric use, and amending Regulation (EEC) No 1768/92,
Directive 2001/20/EC Directive 2001/83/EC and Regulation (EC) No 726/2004 (as amended).
http://ec.europa.eu/enterprise/sectors/pharmaceuticals/files/eudralex/vol-1/reg_2006_1901/
reg_2006_1901_en.pdf. Accessed 11 Jan 2010
Part III
Specific Pediatric Pharmacology
Fetal Medicine and Treatment
Magnus Westgren
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 272
2 Basic Principles for Placental transfer of Drugs and Fetal Pharmacokinetics . . . . . . . . . . . . 272
3 Different Fetal Treatment Strategies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
3.1 Fetal Transfusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 274
3.2 Fetal Stem Cell Therapy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 275
3.3 Fetal Analgesia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 276
3.4 Fetal Medical Treatment Due to Fetal Heart Arrhythmias . . . . . . . . . . . . . . . . . . . . . . . . . . 278
3.5 Corticosteroids for Accelerated Fetal Lung Maturation . . . . . . . . . . . . . . . . . . . . . . . . . . . . 279
3.6 Medical Treatment for Intrauterine Fetal Virus Infections . . . . . . . . . . . . . . . . . . . . . . . . . 279
3.7 Medical Treatment for Fetal Goiter . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 280
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 281
Abstract Fetal medicine covers a broad spectrum of conditions that can be

diagnosed before birth. Different disorders will require different treatment
strategies and there is often an important ontogenetic aspect on how and when
treatment can be implemented. Due to the limited availability there is a general lack
of knowledge on how pharmacotherapy can be provided in the most efficient way.
Until recently most knowledge about how different drugs are transferred and
metabolized in the human fetus is based on very limited observational studies on
concentrations of drugs in fetal blood and other fetal compartments. It might be that
the rapid development of other non-invasive methods for fetal diagnostics such as
isolation of fetal DNA and RNA in maternal serum, NMR imaging and other
techniques could in the future be explored in fetal pharmacotherapy.
M. Westgren
Division of Obstetrics and Gynecology, Department of Clinical Science, Intervention and
Technology, Centre for Fetal Medicine, Karolinska University Hospital, Karolinska Institutet,
S-141 86 Stockholm, Sweden
e-mail: magnus.westgren@ki.se

272 M. Westgren
Introduction of new treatment strategies are often based on extrapolation from

experience in neonates and adults. However some fetal conditions are very specific
for this time period in life. This especially entails disturbances in development as
malformations, early growth restriction and several congenital disorders. Here it
might be required to introduce new treatment strategies without any previous expe-
rience in humans. Example of this ethical dilemma is gene therapy for lung growth in
severe cases of diaphragmatic hernia and early growth restriction. The risk–benefit
issues need to be discussed in all these alternatives. However, it is likely that the
concept of the human fetus as a potential patient is still in its infancy and with an
improved understanding about fetal patho-physiology there will be a continued need
for better knowledge of pharmacotherapy during this crucial time period in life.
Keywords Fetal therapy • Fetal medicine • Congenital anomalies • Fetal

analgesia • Gene therapy • Stem cell therapy
1 Introduction
During the last decades fetal medicine has evolved from traditional obstetrics.
Cornerstones in this process have been the development of effective fetal diagnostic
means such as advanced ultrasound techniques, cytogenetics, and more recently
molecular genetics. Improved knowledge about fetal conditions has formed the
diagnostic foundation for different fetal treatment strategies.
The pioneering work within this new field was made by physicians and scientists
from New Zealand. Liley, frustrated by severely hydropic fetuses in rhesus
immunized mothers and a devastating high stillborn rate among these patients,
introduced intrauterine transfusions in 1959 (Liley 1963). He showed that it was
possible to rescue severely ill fetuses, and his contribution is not only that he
developed effective treatment but also that the human fetuses could be regarded
as a patient accessible for diagnosis and therapy.
Effective non-invasive fetal therapy was introduced by his countryman Liggins
(Liggins 1969; Liggins and Howie 1972). He reported on the effectiveness of
transplacental steroid treatment to the mother in preventing respiratory stress syn-
drome. Intrauterine transfusion and corticosteroids are still by far the most common
modalities for fetal therapy. There are continuous attempts to introduce new treat-
ment strategies, and the present chapter will give a brief review on this topic.
2 Basic Principles for Placental transfer of Drugs

and Fetal Pharmacokinetics
Most drugs move across the placenta by simple diffusion and the degree of
diffusion depends on the chemical properties and concentration of the unbound
drug (Boreus 1967; Yaffe 1980). Drugs with a molecular weight less than 1,000 are
Fetal Medicine and Treatment 273
lipid soluble and these drugs penetrate the trophoblast barrier easily and can reach
the fetal circulation readily (Juchau and Dyer 1972). With advancing gestational
age, drug transfer is increasing. Any drug in maternal blood will cross the placenta,
especially if maternal effective drug concentrations have been maintained under
extended periods (Leeder 2009). Different pathological conditions affecting the
placenta such as preeclampsia, preterm premature rupture of membranes, etc. can
affect the placental blood flow and thus placental transfer. Some drugs will be
metabolized and biotransformed in the placenta as occurs in liver. Drugs may also
induce or inhibit placental enzymes necessary for metabolic conversion of exoge-
nous substances.
For most drugs that cross the placenta fetal concentration will be 50–100% of the
mother concentration. When steady state is reached, the fetal concentration can
be higher than in the mother. The complete exposure of the drug and its metabolites
are more important than the rate of placental transportation. In the human fetus
proportionally more blood is directed to the brain, and the blood–brain permeability
is greater in the fetus than in the adult (Myllynen et al. 2009). Consequently, the
developing brain is more vulnerable to circulating drug levels. Despite preferential
circulation to the brain, the distribution eventually becomes diffuse. Plasma protein
concentration and protein binding capacity is lower in the fetus than in the mother
leading to higher unbound drug concentration. Thus, conclusions about drug dispo-
sition in the fetus based on maternal and fetal serum concentrations may not
accurately reflect true fetal pharmacokinetics.
Receptor and the strength of the receptor response for different drugs
may differ with advancing gestational age. Several fetal organs are capable of
substantial metabolic activity, but drug metabolism does preferentially take
place in the liver. Human fetal liver microsomes have significant P-450 levels
and NADPH cytochrome c reductase (Yaffe 1980). Oxidation and reduction
reaction have been observed already from the first trimester but are probably less
than in the adult. Therefore direct effects of drugs can be more prolonged in the
fetus than in the mother. The excretion in the fetus is slower than in the mother.
Primary routes for excretion are placenta and amniotic fluid. The placental
transfer of the drugs from the fetus to the mother is the primary route in early
pregnancy while drug elimination in late pregnancy depends on the immature
fetal kidneys.
The transplacental route is the standard means of administrating drugs to the
fetus. Exceptions are if the drug crosses the placenta poorly, or if the disease of
the fetus affects the placental transfer, the fetus is moribund requiring fast interven-
tion, or if severe maternal side effect can be anticipated. Direct administration to the
fetus can be performed in several ways; intraamniotically, intravascularly, intra-
muscularly, and finally intraperitoneally (Table 1). There is limited information on
how the route for direct administration affects the pharmacokinetics of different
drugs.
274 M. Westgren
Table 1 Principal routes for Route Example in clinical practice

drug administration in human
fetuses Maternal Digoxin
Sotalol
Flecainide
Intraamniotic Thyroxin
Intravenously (fetus) Alfentanil
Digoxin
Plasma products
Intramuscular (fetus) Curare
Alfentanil
Intraperitoneal Curare
Alfentanil
3 Different Fetal Treatment Strategies
3.1 Fetal Transfusions
Fetal transfusions were introduced in the 1960s. From the beginning, blood was
transfused into the intraperitoneal cavity, but later intravascular transfusions were
introduced. In 1984, Rodeck published a report on fetoscopically guided intravas-
cular transfusions (Rodeck et al. 1981). Later Bang introduced ultrasound-guided
fetal transfusions, and this technique is considered common practice fetal medicine
today (Bang et al. 1982). The most common sites for intravascular transfusions are
the umbilical vein close to the placental insertion, umbilical vein in a free lope, and
the intrahepatic part of the umbilical vein. The free lope approach is associated with
a higher rate of complications; i.e., bleedings into the amniotic cavity. Puncturing
of the umbilical vein is associated with certain risks, and the procedure-related
complication rate is about 3%. The most common reason for fetal transfusions is
severe erythrocyte immunization. Another well-known indication is fetal anemia
due to parvovirus infection.
Patients at risk of fetal anemia are monitored non-invasively with Doppler flow
recordings of the cerebral arteries. In case of signs of anemia (increased velocities),
the patient will undergo cordocentesis with direct measurement of fetal hemoglobin
concentration. If the fetus is anemic, a blood transfusion will be carried out. Mostly
O negative blood with high hematocrit will be used and the amount of blood
required will be calculated from the initial hemoglobin value and the size of the
fetus. Usually, repeated transfusions are required and typically a patient will
undergo treatment every second week. Most centers for fetal medicine today prefer
to perform transfusions until the 33rd–34th week. Intravascular transfusions can be
commenced as early in the 18th–19th week of gestation, and such a patient will
require 7–8 transfusions until she can be safely delivered. Depending on the degree
of anemia and if the fetus has developed hydrops survival rate differ, but most units
report survival rates in the range of 80–95% (Westgren et al. 1988; Weiner et al
1991). Long-term outcome of children treated in utero for fetal anemia is favorable,
and it is amazing how the human fetus can withstand very severe anemia.
Other blood products have been transfused for other fetal disorders. Platelets
have been administrated in cases of fetal alloimmune thrombocytopenia. The risk
for bleedings in increased in such cases, and today most fetal medicine units avoid
cordocentesis in this condition. In cases of non-immune hydrops of unknown
origin, plasma and albumin have been given to the fetus. However, this is highly
experimental and is practiced in very few centers.
3.2 Fetal Stem Cell Therapy
The fetus and its environment are unique in many ways. This has led to the
assumption that the fetus is a potential suitable candidate for stem cell
transplantations (Touraine et al 1989; Flake and Zanjani 1999). The arguments
for fetal transplantations are the following: In some disorders the fetus is severely
affected already during fetal life. An example of such a condition is homozygous
alpha-thalassemia, almost always lethal before birth. Furthermore, from experience
with bone marrow transplantation in cases of metabolic disorders or hemoglobi-
nopathies, it is quite clear that the earlier in life a transplantation is carried out the
better the prognosis. Thus, there are many arguments favoring early stem cell
transplantation. The immunological naivety in the early gestation fetus has given
rise to the concept of fetal tolerance, i.e., the inability to raise an immunological
response against foreign antigens. During fetal life, the developing immune system
is educated to distinguish between autologous and foreign antigens. However, if
introduced early enough, foreign antigens can be recognized as self and not
rejected. Consequently, in theory it should be possible to carry out fetal stem cell
transplantations without chemotherapy and myoablation and across HLA barriers.
Furthermore, during normal fetal life, naturally occurring stem cells expand and
migrate and seed different anatomical compartments. An example of this relation-
ship is the development of hematopoietic stem cells that originally are located in
the dorsal aorta, from the 5th week in the liver and from week 12 in the bone
marrow. These different compartments provide a potential and specialized support-
ive environment for engraftment, proliferation, and differentiation of stem cells.
Exogenous administrated stem cells could possibly take advantage of these favor-
able conditions. Other arguments are that the intrauterine environment is sterile and
very protective and the small size of the fetus ensures a much larger cell dose on a
per kilogram basis than can be achieved after birth.
In-utero stem cell transplantation has been studied in several different animal
models, most extensively in mouse, sheep, canine, and primates (Zanjani et al. 1992;
Harrison et al. 1989; Blakemore et al. 2004). With few exceptions mixed chimerism
of different percentage (0.5–30%) is achieved in these models. Thus it seems
possible to perform intrauterine transplantation if it is done early during fetal life.
276 M. Westgren
In humans the experience with fetal stem cell transplantation is limited, and we
know about 50 cases reported so far. Most of these cases have been reported
adequately in previous reviews on this topic (Tiblad and Westgren 2008; Westgren
2009). The most successful group of patients transplanted in utero are those with
immunodeficiencies. Engraftment has been reported in 8 of 12 cases, and several of
these children have had a benign clinical course. In comparison with postnatal
transplantation, in-utero transplantation is associated with several advantages. It is
less expensive and the recipient does not need any chemotherapy or radiation.
Furthermore, it might reduce the risk for graft-versus-host disease, a problem
associated with SCID, and it has an obvious psychological advantage before
postnatal transplantations (Flake et al. 1996; Westgren et al. 2002).
In quite a number of cases with hemoglobinopathies and storage disorders,
intrauterine transplantation has convincingly failed (Westgren et al. 1996). In a
few of these cases engraftment has occurred but the phenotype has not been
changed. The reason why intrauterine transplantation has failed in these cases is
unclear but it seems that the human fetal immunological system is more mature than
has been anticipated and failure of transplant could also be considered. In recent
years, there are some reports on successful transplantation of mesenchymal stem
cells (MSC) for osteogenesis imperfecta (Le Blanc et al. 2005). Interestingly, some
of these transplantations have been performed across HLA barriers and rather late
during gestation. It seems that MSC have unique immunological properties and if
these results will be confirmed in larger studies MSC could be used for transplanta-
tion between mismatched individuals.
In conclusion, intrauterine transplantation is a highly experimental type of
fetal treatment. Widespread clinical application is premature based on the limited
success that has been achieved so far.
3.3 Fetal Analgesia
Invasive therapeutic options have drawn attention to the need of fetal analgesia.
Currently no defined evidence-based fetal anesthesia or analgesia protocol exists
for these procedures. Whether the fetus can respond to noxious stimulus with
pain is based on our current knowledge on neurodevelopment of anatomical
pathways as well as observational studies on fetal behavior at pain exposition
in utero.
It has been claimed that an intact spinothalamic connection exists as early as in
the seventh week of gestation (Lagercrantz and Changeux 2009; Derbyshire
2006). At this stage, no laminal structure is present connecting thalamus to cortex,
and without thalamic projection to the cortex the neuronal cells cannot process
noxious information from the periphery. The first projections from thalamus
to cortex appear at 12th–16th week. However, not until the 23rd–25th week
afferent neurons penetrate and form synapses to the cortex. Theoretically, the
spinothalamic projections into the cortex may provide the necessary anatomical
foundation for pain experience in the human fetus. That the human fetus is
capable to experience pain from late second trimester is also supported by several
observational studies.
Withdraw reflexes at needling procedures as a sign of nociceptial reaction can be
observed from the 19th week. Fisk et al. showed from their experience on punctur-
ing the human fetus with a needle an increase in cortisol, beta-endorphin, and
noradrenalin in cord blood from the 20th week (Giannakoulopoulos et al. 1994;
Fisk et al. 2001; Teixeira et al. 1999). In preterm children, face reactions similar to
that seen in adults experiencing pain can be observed from the 28th week (Van de
Velde et al. 2006).
Thus, there is evidence suggesting that analgesia to blunt nociceptive responses
in utero should be used from the 20th–23rd week of gestation. However, although
most centers performing invasive fetal procedures are using analgesia, there is a
general lack of information on how it may be safely and effectively administrated.
Opioid agonists have been widely used and have been given directly intravenously
to fetuses before open surgery. Direct administration into the intravascular space of
the fetus is known to be associated with certain risks. Direct intravenous adminis-
tration has later in most centers been replaced by intramuscular administration, but
due to slower absorption this will prolong the procedure and might require multiple
injections of the fetus (Van de Velde et al. 2006). In our center, we have since more
than a decade used intraperitoneal administration for administration of different
pharmacological agents at invasive procedures (cisatracurare 0.30 mg/kg, alfentanil
0.015 mg/kg) after the 20th week of gestation. The intraperitoneal cavity is easy
to puncture and rapid absorption enables us to perform fetal procedures within
5 min after administration without any sign of fetal distress. Other routes to
consider is intra amniotic where it was recently shown that intra-amniotic sufentanil
is easily absorbed by the sheep fetus and it was suggested that this route might
provide a simple and fast method for fetal analgesia (Van de Velde et al. 2005;
Strumper et al. 2003).
Different fetal procedures may require a different type of analgesia. In open fetal
surgery, inhalation agents to the mother provide effective maternal and fetal
analgesia and anesthesia. In addition, uterine relaxation is often obtained by these
agents. Most endoscopic procedures are performed under regional or local maternal
analgesia. If analgesia and paralysis of the fetus are required, this is usually
obtained by injection of opioids and/or muscle relaxants. If only immobilization
of the fetus is wanted during the procedure, maternally administrated remifentanil
resulted in effective maternal sedation and fetal immobilization.
The potential benefit of the fetus with analgesia and anesthesia needs to be
balanced against the risk for the mother. In such equation it is important to consider
the old obstetric dictum that the mother’s life should always be at highest priority.
Finally, we are lacking information on long-term outcome of fetuses exposed for in-
utero procedures. In this context pain experience during fetal life is an area of
concern that requires much more attention in the future.
278 M. Westgren
3.4 Fetal Medical Treatment Due to Fetal Heart Arrhythmias
The most common reason for medical treatment is fetal tachycardias. It is defined as
a tachycardia of non-sinus origin with a heart frequency exceeding 180–200 beats
per minute. There are several variants with different electrophysiological back-
ground and prognosis. The most common is an atrioventricular re-entry tachycardia
caused by the presence of an accessory pathway between the atrium and the
ventricle. Another type is the one with atrium flatter with re-entry in the atrium
wall. Altogether these two types represent approximately 95% of all cases of fetal
tachycardias (Simpson and Sharland 1998; Carvalho et al. 2007; Krapp et al. 2003).
Usually the mother will not experience any symptoms and the high fetal heart
rate is picked up at a routine antenatal check-up in weeks 28–34. In some cases, the
fetus has developed signs of heart failure with polyhydramniosis and/or reduced
fetal movements. Ultrasound examination will in a third of these cases reveal
increased amount of fluid in the fetus or in more severe cases full blown hydrops.
The reason for the heart failure is an impaired diastolic filling of the ventricules
when the heart rate increases. Consequently, cardiac output decreases and the
intraatrial and central vein pressure increases. The increased pressure in the atria
predisposes for atrial flatter.
Management of fetal tachycardia requires knowledge about the electrophysiologi-
cal background and the hemodynamic situation of the fetus. The degree of heart
failure or hydrops will be in most cases an important denominator for prediction of
the prognosis. Other issues to consider are if the tachycardia is continuous or
intermittent, frequency of the ventricles, relationship between atrial and ventricular
systolic phase, heart malformations, and finally the gestational age. If the fetus has no
hemodynamic signs of heart failure, different options can be considered. Maternal
medication and treatment across the placenta, direct therapy to the fetus, delivery and
treatment of the newborn, or if tachycardia is intermittent just to observe. To deliver a
fetus with heart failure is usually a worse alternative than treating the fetus in utero.
In absence of hydrops, first line drug is digoxin. In many cases digoxin needs to
be combined with sotalol or flecainide (Oudijk et al. 2000; Jaeggi et al. 2004).
Approximately 85% of the cases will convert to normal heart rate on this treatment,
and these children will do well. In fetuses with hydrops there is poor transplacental
passage of digoxin, and in these cases sotalol is to be recommended. Another option
is to treat the fetus with direct dixoxin administration.
Fetal bradycardia is defined as a heart rate less than 100 bpm. Short episodes of
bradycardia is a common phenomenon and of no significance. In cases of continued
ventricular arrhythmia, treatment with beta blockers could be considered. A severe
form of bradycardia is due to a complete A–V block. In approximately 50% of these
cases, it is combined with heart malformations. In cases with no malformations,
the condition is usually caused by anti-Ro and Anti-L antibodies (Bergman et al.
2009; Strandberg et al. 2008). Transplacental treatment with digoxin for improve-
ment of ventricular contractions, beta stimulator for increasing the heart rate and
dexamethasone for anti-inflammation could be considered in these cases.
3.5 Corticosteroids for Accelerated Fetal Lung Maturation
Respiratory distress syndrome (RDS) is a serious consequence of preterm delivery

and causes significant mortality and morbidity. Liggins when investigating dexa-
methasone and preterm labor in lambs found evidence of accelerated lung matura-
tion (Liggins 1969). Later Liggins and Howie performed the first prospective
randomized study on the value of antenatal corticosteroids and were able to
demonstrate prevention of RDS (Liggins and Howie 1972). Since then a large
number of prospective randomized trials have been carried out and confirmed
Liggin’s original observation and hypothesis. An extensive Cochrane review and
meta-analysis was published in 2006 on the use of antenatal steroids (Dalziel 2008).
Treatment with antenatal corticosteroids reduces the risk of neonatal death, RDS,
cerebroventricular hemorrhages, necrotising enterocolitis, infectious morbidity,
and need of respiratory support and neonatal intensive care. There is evidence on
benefit from 24 to 34 weeks. There is also evidence on beneficial effect in cases of
premature rupture of membranes and in hypertensive disorders.
It seems that this beneficial effect is achieved by single-dose antenatal
corticosteroids. Thus, corticosteroids are by far the most common used drugs for
fetal therapy. It seems safe for the fetus and mother, but long-term follow-up of the
children to adulthood after corticosteroid exposition in utero are still needed to
ensure the long-term safety of this treatment.
3.6 Medical Treatment for Intrauterine Fetal Virus Infections
Intrauterine cytomegalovirus (CMV) infection is a serious condition with far-

reaching consequences for the fetus. Infection during pregnancy occurs in 1% of
nonimmune and 5% of immune pregnant women, with a vertical transmission of
30% and 0.2–8%, respectively. Intrauterine infection is associated with severe
growth restriction, microcephaly, jaundice, hepatosplenomegaly, and severe throm-
bocytopenia. Approximately 30% of the fetuses with symptoms will die, and of the
remainder, a substantial number will develop neurological handicaps (Lazzarotto
et al. 2000; Lanari et al. 2006). Recently there are also reports on an association
between CMV infections and neuroblastomas later during infancy (S€oderberg-
Nauclér 2008). Thus congenital CMV infection represents a major medical chal-
lenge in fetal medicine. Jacquemard et al. treated affected cases with maternal oral
administration of valaciclovir (VACV) (Jacquemard et al. 2007). They could
demonstrate that they achieved therapeutic concentrations in maternal and fetal
blood. The viral load decreased significantly after 1–12 days of treatment. They
could not prove the therapeutic effect which needs to be addressed in a prospective
randomized study.
280 M. Westgren
There is limited information on pharmacokinetics of VACV. VACV is an

orally administrated prodrug of acyclovir with improved oral bioavailability and
pharmacokinetic properties. A substantial number of fetuses have been exposed
for acyclovir with no teratogenic effects. Therefore acyclovir has been given in
serious maternal complications such as pneumonia and herpes encephalitis, etc.
(Frenkel et al. 1991; Stone et al. 2004). There are no data on VACV and the risk
for the fetus, but based on the outcome from acyclovir exposition, the risk seems
low. Another option treatment strategy for CMV infection is to provide CMV
hyperimmune globulin. Promising results have been published but these
studies needs to be confirmed in controlled trials (Nigro et al. 2005; Adler and
Nigro 2009).
3.7 Medical Treatment for Fetal Goiter
Fetal goiter may be associated with hypo- or hyperthyroidism. With high resolu-
tion ultrasound the thyroid gland can easily be visualized and consequently most
cases of fetal goiter are diagnosed in utero (Ballabio et al. 1989). Congenital
hypothyroidism is rare and is mostly caused by thyroid dysgenesis. Transient fetal
hypothyroidism is usually caused by maternal antithyroid drug intake, commonly
carbimazole or propylthiouracil due to Grave’s disease. Fetal hyperthyroidism
is usually caused by maternal Grave’s disease. Some of these mothers have
thyroid-stimulating immunoglobulins, and sometimes these stimulating immuno-
globulins cross the placenta and may activate fetal TSH receptors (Mitsuda et al.
1992).
Timely diagnosis and treatment are important in cases of fetal thyroid
disturbances. The diagnosis of fetal goiter is usually quite straightforward. It
warrants a thorough evaluation of other thyroid-associated manifestations such as
tachycardia, polyhydramniosis, and growth restriction.
Fetal thyroid status can be assessed by cordiocentesis and direct blood sampling.
If the fetal goiter is found in an euthyroid mother, it is usually possible to treat the
mother with antithyroid drugs and get a good response in the fetus. However, the
mother usually needs T4 supplementation during the treatment. If the fetal goiter
is diagnosed in a mother with Grave’s disease it is necessary to evaluate if the
goiter is a result from transplacental passage of thyroid-stimulating antibodies. At
concomitant fetal hyperthyroidism, the mother usually requires higher doses
of antithyroid drugs. In cases of need for T4 supplementation to the fetus,
direct administration of thyroid hormones can be carried out by intra-amniotic,
intravascular or intramuscular routes. Since the fetus in this situation often requires
repeated injections the intra-amniotic route is preferable. Adequate fetal thyroid
replacement therapy can be achieved by intra-amniotic administration of
250–500 mg T4 at 7–10 days intervals.
References
Adler SP, Nigro G (2009) Findings and conclusions from CMV hyperimmune globulin treatment
trials. J Clin Virol 46(Suppl 4):S54–S57
Ballabio M, Nicolini U, Jowette T, Ruiz de Elvira MC, Ekins RP, Rodeck CH (1989) Maturation
of thyroid function in normal human foetuses. Clin Endocrinol 31(5):565–571
Bang J, Bock JE, Trolle D (1982) Ultrasound guided fetal intravenous transfusion for severe rhesus
haemolytic disease. Br Med J 284:373–374
Bergman G, Eliasson H, Bremme K, Wahren-Herlenius M, Sonesson SE (2009) Anti-Ro52/SSA
antibody-exposed fetuses with prolonged atrioventricular time intervals show signs of
decreased cardiac performance. Ultrasound Obstet Gynecol 34(5):543–549
Blakemore K, Hattenburg C, Stetten G et al (2004) In utero hematopoietic stem cell transplantation
with haploidentical donor adult bone marrow in a canine model. Am J Obstet Gynecol
190:960–973
Boreus LO (1967) Pharmacology of the human fetus: dose-effect relationship for acetylcholine
during ontogenesis. Biol Neonat 11:328–337
Carvalho JS, Prefumo F, Ciardelli V et al (2007) Evaluation of fetal arrhythmias from simulta-
neous pulsed wave Doppler in pulmonary artery and vein. Heart 93:1448–1453
Dalziel RD (2008) Antenatal corticosteroids for accelerating fetal€
o lung maturation for women at
risk of preterm birth. The Cochrane collaboration. Cochrane Library 4:1–166
Derbyshire WGS (2006) Can fetuses feel pain? BMJ 332(7546):909–912
Fisk NM, Gitau R, Teixeira JM, Giannakoulopoulos X, Cameron AD, Glover VA (2001) Effect of
direct fetal opioid analgesia on fetal hormonal and hemodynamic stress response to intrauterine
needling. Anesthesiology 95:828–835
Flake AW, Zanjani ED (1999) In utero hematopoietic stem cell transplantation: ontogenic
opportunities and biologic barriers. Blood 94:2179–2191
Flake AW, Roncarolo MG, Puck JM et al (1996) Treatment of x-linked severe combined immuno-
deficiency by in utero transplantation of paternal bone marrow. N Engl J Med 335:1806–1810
Frenkel LM, Brown ZA, Bryson YJ, Corey L, Unadkat JD, Hensleigh PA, Arvin AM, Prober CG,
Connor JD (1991) Pharmacokinetics of acyclovir in the term human pregnancy and neonate.
Am J Obstet Gynecol 164(2):569–576
Giannakoulopoulos X, Sepulveda W, Kourtis P, Glover V, Fisk NM (1994) Fetal plasma cortisol
and beta-endorphin response to intrauterine needling. Lancet 344:77–81
Harrison MR, Slotnick RN, Crombleholme TM et al (1989) In-utero transplantation of fetal liver
haemopoietic stem cells in monkeys. Lancet 2:1425–1427
Jacquemard F, Yamamoto M, Costa J-M, Romand S, Jaqz-Aigrain E, Dejean A, Daffos F, Ville Y
(2007) Maternal administration of valaciclovir in symptomatic intrauterine cytomegalovirus
infection. BJOG 114(9):1113–1121
Jaeggi ET, Fouron JC, Silverman ED et al (2004) Transplacental fetal treatment improves the
outcome of prenatally diagnosed complete atrioventricular block without structural heart
disease. Circulation 110:1542–1548
Juchau MR, Dyer DC (1972) Pharmacology of the placenta. Pediatr Clin North Am 19:65–69
Krapp M, Kohl T, Simpson JM et al (2003) Review of diagnosis, treatment, and outcome of fetal
artrial flutter compared with supraventricular tachycardia. Heart 89:913–917
Lagercrantz H, Changeux J-P (2009) The emergence of human consciousness: from fetal to
neonatal life. Pediatr Res 65(3):255–260
Lanari M, Lazzarotto T, Venturi V, Papa I, Gabrielli L, Guerra B et al (2006) Neonatal cytomega-
lovirus blood load and risk of sequelae in symptomatic and asymptomatic congenitally infected
newborns. Pediatrics 117:76–83
Lazzarotto T, Varani S, Guerra B, Nicolosi A, Lanari M, Landini MP (2000) Prenatal indicators of
congenital cytomegalovirus infection. J Pediatr 137:90–95
282 M. Westgren
Le Blanc K, Gotherstrom C, Ringden O et al (2005) Fetal mesenchymal stem-cell engrafment in

bone after in utero transplantation in a patient with severe osteogenesis imperfect. Transplan-
tation 79:1607–1614
Leeder JS (2009) Developmental pharmacogenetics a general paradigm for application to neonatal
pharmacology and toxicology. Clin Pharmacol Ther 86(6):678–682
Liggins GC (1969) Premature delivery of fetal lambs infused with glucocorticoids. J Endocrinol
45:515–523
Liggins GC, Howie RN (1972) A controlled trial of antepartum glucocorticoid treatment for
prevention of the respiratory distress syndrome. Pediatrics 50:515–525
Liley AW (1963) Intrauterine transfusion of foetus in haemolytic disease. Br Med J ii:
1107–1109
Mitsuda N, Tamaki H, Amino N, Hosono T, Miyai K, Tanizawa O (1992) Risk factors for
developmental disorders in infants born to women with Graves’ disease. Obstet Gynecol 80
(3 Pt 1):359–364
Myllynen P, Immonen E, Kummu M, V€ah€akangas K (2009) Developmental expression of drug
metabolizing enzymes and transporter proteins in human placenta and fetal tissues. Expert
Opin Drug Metab Toxicol 5(12):1483–1499
Nigro G, Stuart P, La Torre R, Best A (2005) Passive immunization during pregnancy for
congenital cytomegalovirus infection. N Engl J Med 353:13–21
Oudijk MA, Michon MM, Kleinman CS et al (2000) Sotalol in the treatment of fetal dysrhythmias.
Circulation 101:2721–2726
Rodeck CH, Kemp JR, Holman CA, Whitmore DN, Karnicki J, Austin MA (1981) Direct
intravascular fetal blood transfusion by fetoscopy in severe Rhesus isoimmunisation. Lancet
1:625–627
Simpson JM, Sharland GK (1998) Fetal tachycardias: management and outcome of 127 consecu-
tive cases. Heart 79:576–581
S€oderberg-Nauclér C (2008) HCMV microinfections in inflammatory diseases and cancer. J Clin
Virol 41(3):218–223
Stone KM, Reiff-Eldridge R, White AD, Cordero JF, Brown Z, Alexander ER, Andrews EB
(2004) Pregnancy outcomes following systemic prenatal acyclovir exposure: conclusions from
the international acyclovir pregnancy registry, 1984–1999. Birth Defects Res A Clin Mol
Teratol 70(4):201–207
Strandberg L, Winqvist O, Sonesson SE, Mohseni S, Salomonsson S, Bremme K, Buyon JP,
Julkunen H, Wahren-Herlenius M (2008) Antibodies to amino acid 200–239 (p200) of Ro52 as
serological markers for the risk of developing congenital heart block. Clin Exp Immunol 154
(1):30–37
Strumper D, Durieux ME, Gogarten W, Van Aken H, Hartleb K, Marcus MA (2003) Fetal plasma
concentrations after intraamniotic sufentanil in chronically instrumented pregnant sheep.
Anesthesiology 98:1400–1406
Teixeira JM, Glover V, Fisk NM (1999) Acute cerebral redistribution in response to invasive
procedures in the human fetus. Am J Obstet Gynecol 181:1018–1025
Tiblad E, Westgren M (2008) Fetal stem-cell transplantation. Best Pract Res Clin Obstet Gynaecol
22(1):189–201
Touraine JL, Raudrant D, Royo C et al (1989) In-utero transplantation of stem cells in bare
lymphocyte syndrome. Lancet I:1382
Van de Velde M, Van Schoubroech D, Lewi LE, Marcus MAE, Jani JC, Missant C et al (2005)
Remifentanil for fetal immobilization and maternal sedation during fetoscopic surgery:
a randomized double blind comparison with diazepam. Anesth Analg 101:251–258
Van de Velde M, Jani J, De Buck F, Deprest J (2006) Fetal pain preception and pain management.
Semin Fetal Neonatal Med 11(4):232–236
Weiner CP, Williamson RA, Wenstrom KD, Sipes SL, Widness JA, Grant SS et al (1991)
Management of fetal hemolytic disease by cordocenteses. II. Outcome of treatment. Am J
Obstet Gynecol 165:1302–1307
Westgren M (2009) Intrauterine transplantation. Blood 113(19):4484

Westgren M, Jabbar F, Larsen JF, Rahman F, Selbing A, Stangeberg M (1988) Introduction of a
programme for intravascular transfusions at severe rhesus isoimmunization. J Perinat Med
16:417–422
Westgren M, Ringden O, Eik-Nes S et al (1996) Lack of evidence of permanent engraftment after
in utero fetal stem cell transplantation in congenital hemoglobinopathies. Transplantation
61:1176–1179
Westgren M, Ringden O, Bartmann P et al (2002) Prenatal t-cell reconstitution after in utero
transplantation with fetal liver cells in a patient with x-linked severe combined immunodefi-
ciency. Am J Obstet Gynecol 187:475–482
Yaffe SJ (1980) Clinical implications of perinatal pharmacology. Eur J Clin Pharmacol 18(1):3–7
Zanjani ED, Ascensao JL, Flake AW et al (1992) The fetus as an optimal donor and recipient of
hemopoietic stem cells. Bone Marrow Transplant 10(Suppl 1):107–114
Fetal Risks of Maternal Pharmacotherapy:
Identifying Signals
Gideon Koren
Contents
1 Principles of Teratology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 285
2 Confounding Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 288
2.1 Sample Size . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
2.2 Bias by Indication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 289
2.3 Time of Enrollment as a Bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
2.4 Bias in Retrospective Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
2.5 Recall Bias . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 290
2.6 Bias in Not Including Elective Abortion Data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 291
2.7 Bias in Retrospective Ascertainment of Maternal Lifestyle . . . . . . . . . . . . . . . . . . . . . . . . . 291
2.8 Bias Against the Null Hypothesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 292
3 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 293
Abstract Pregnant women may be exposed to a variety of medications that may

exert toxic or teratogenic effects on the fetus. Since the thalidomide disaster,
physicians and pregnant women tend to withhold medications during pregnancy,
although the risk of teratogenic effect from most drugs in therapeutic doses is
nonexistent. This chapter will review the principles of teratology and the
pharmacoepidemiological evidence for drug safety/risk in human gestation.
Keywords Teratology • Fetal safety • Fetus • Drugs • Teratogenicity • Bias
G. Koren (*)
The Motherisk Program, Division of Clinical Pharmacology and Toxicology, Hospital for Sick
Children, University Avenue 555, Toronto M5G 1X8, ON, Canada
e-mail: gidiup_2000@yahoo.com

286 G. Koren
1 Principles of Teratology
Congenital defects occur in 1–3% of the general population. Of the major defects,
about 25% are of genetic origin (genetically inherited diseases, new mutations and
chromosomal abnormalities) and 65% are of unknown etiology (multifactorial,
polygenic, spontaneous errors of development and synergistic interactions of
teratogens). Only 2–3% of malformations are thought to be associated with drug
treatment (Table 1). The remaining defects are related to other environmental
exposures including infectious agents, maternal disease states, mechanical
problems, and irradiation (Koren et al. 1998).
The importance of timing of drug exposure is critical; the effect produced by
a teratogenic agent depends upon the developmental stage in which the conceptus is
exposed. The following phases in human development must be recognized:
• The “all or none” period, the time from conception until somite formation.
Insults to the embryo in this phase are likely to result in death and miscarriage
or intact survival. The embryo is undifferentiated, and repair and recovery are
possible through multiplication of the still totipotential cells. Exposure to
teratogens during the presomitic stage usually does not cause congenital
malformations unless the agent persists in the body beyond this period.
• The embryonic period, from 18 to 60 days after conception when organogenesis
occurs. This is the period of maximum sensitivity to teratogenicity since tissues
are differentiating rapidly and damage becomes irreparable. Exposure to terato-
genic agents during this period has the greatest likelihood of causing a structural
anomaly. Critically because half of all pregnancies are unplanned, many women
taking drugs at that stage are not aware of their risks.
• The fetal phase, from the end of the embryonic stage to term, when growth and
functional maturation of formed organs and systems occurs. The only organ that
continues to differentiate until birth is the brain and hence ethanol and drugs of
abuse may adversely affect the fetal brain at any stage. Teratogen exposure in
this period will affect fetal growth (e.g., intrauterine growth restriction) and the
size or function of an organ, rather than cause gross structural anomalies.
Many organ systems continue structural and functional maturation long after
birth. Most of the adenocarcinomas associated with first trimester exposure to
diethylstilbestrol occurred many years later.
Teratogens must reach the developing fetus in sufficient amounts to cause their
effects. Large molecules with a molecular weight greater than 1,000 (e.g., heparin)
do not easily cross the placenta into the embryonic–fetal bloodstream. Other factors
influencing the rate and extent of placental transfer of drugs include polarity, lipid
solubility, and the existence of a specific protein carrier (e.g., P-glycoprotein).
Every year scores of new pharmaceuticals enter the market, almost never with
human fetal safety data. Such data typically accumulate during the first years of
clinical use, in the form of case reports, case series, prospective and retrospective
cohorts, and case control studies. All of these methods suffer from serious sources
Fetal Risks of Maternal Pharmacotherapy: Identifying Signals 287
Table 1 Teratogenic drugs and chemicals in humans

Drug Adverse effects
Angiotensin converting Adverse effects related to hemodynamic effects of ACEI and
enzyme inhibitors angiotensin II antagonists on the fetus. In late pregnancy, ACEI
(ACEI) and fetopathy: intrauterine renal insufficiency, neonatal hypotension,
angiotensin II oliguria with renal failure, hyperkalemia, complications of
antagonists oligohydramnios (i.e., fetal limb contractures, lung hypoplasia, and
craniofacial anomalies), prematurity, intrauterine growth restriction
and fetal death. Questionable teratogenic risk with first trimester
exposure of cardiovascular and CNS malformations
Antineoplastic agents A significant increase in the incidence of various fetal malformations
and early miscarriages following first trimester exposure
Carbamazepine First trimester exposure: 1% risk of neural tube defects (10 baseline
risk) and an increased risk of cardiovascular malformations.
A pattern of malformations similar to the fetal hydantoin syndrome
has also been associated
Cocaine Abruptio placenta, prematurity, fetal loss, decreased birth weight,
microcephaly, limb defects, urinary tract malformations, and poorer
neurodevelopmental performance. Methodological problems make
the findings difficult to interpret. Cocaine abuse is often associated
with poly-drug abuse, alcohol consumption, smoking, malnutrition,
and poor prenatal care. Human epidemiology indicates the risk of
major malformation from cocaine is probably low, but the
anomalies may be severe
Corticosteroids Increased risk of oral cleft
(systemic)
Coumarin First trimester exposure (6–9 week gestation): fetal warfarin syndrome
anticoagulants (nasal hypoplasia and calcific stippling of the epiphyses).
Intrauterine growth restriction and developmental delay (CNS
damage), eye defects and hearing loss. Warfarin embryopathy is
found in up to ½ of the cases where a coumarin derivative was given
throughout pregnancy. Associated with high rate of miscarriage.
Risk of CNS damage due to hemorrhage after the first trimester
Diethylstilbestrol Vaginal clear cell adenocarcinoma in offspring exposed in utero before
18th week (>90% of the cancers occurred after 14 years of age).
High incidence of benign vaginal adenosis. Increased miscarriage
rate and preterm delivery. In males exposed in utero: no signs of
malignancy but genital lesions in 27% and pathologic changes in
spermatozoa in 29%. The drug is not currently available in Canada
Ethanol Fetal alcohol syndrome: growth impairment, developmental delay, and
dysmorphic facies. Cleft palate and cardiac anomalies may occur.
Full expression of the syndrome occurs with chronic daily ingestion
of 2 g alcohol per kg (8 drinks/day) in about ½ and partial effects in
of offspring
Folic acid antagonists: Fetal aminopterin–methotrexate syndrome: CNS defects, craniofacial
aminopterin and anomalies, abnormal cranial ossification, abnormalities in first
methotrexate branchial arch derivatives, intrauterine growth restriction, and
mental retardation after first trimester exposure. Maternal dose of
methotrexate needed to induce defects is probably above 10 mg/
week with a critical period of 6–8 week postconception
(continued)
288 G. Koren
Table 1 (continued)
Drug Adverse effects
Hydantoins (phenytoin) Fetal hydantoin syndrome: craniofacial dysmorphology, anomalies and
hypoplasia of distal phalanges and nails, growth restriction, mental
deficiency, and cardiac defects
Lithium Small increase in risk for cardiac teratogenesis in early gestation (1%).
The risk of Ebstein’s anomaly exceeds spontaneous rate of
occurrence. Fetal echocardiography if exposed in first trimester
Misoprostol First trimester exposure: limb defects and Moebius sequence. Absolute
teratogenic risk: probably low. Uterine contraction inducing activity
Retinoids (acitretin, Systemic exposure: potent human general and behavioral teratogen.
isotretinoin) and Retinoic acid embryopathy: craniofacial anomalies cardiac defects,
megadoses of abnormalities in thymic development and alterations in CNS
vitamin A development. Risk for associated miscarriage: 40%
Tetracyclines Discoloration of the teeth after 17-week gestation when deciduous teeth
begin to calcify. Close to term: crowns of permanent teeth may be
stained. Oxytetracycline and doxycycline associated with a lower
incidence of enamel staining
Thalidomide Malformations limited to tissues of mesodermal origin, primarily limbs
(reduction and defects), ears, cardiovascular system and gut
musculature. Critical period: 34th–50th day after the beginning of
the last menstrual period. A single dose of <1 mg/kg has produced
the syndrome. Embryopathy found in about 20% of pregnancies
exposed in the critical period
Valproic acid First trimester exposure: neural tube defects with 1–2% risk of
meningomyelocele, primarily lumbar or lumbosacral,
cardiovascular malformations and hypospadias. Fetal valproate
syndrome: craniofacial dysmorphology, cardiovascular defects,
long fingers and toes, hyperconvex fingernails and cleft lip, has been
delineated by some investigations. Neurobehavioral teratogen
of challenges, often leading to alarming signals of teratogenicity, only to be found

later to be false.
Because randomized controlled trials are very rarely available in pregnancy, and
almost never during the first trimester of pregnancy, understanding the methodo-
logical difficulties is critical in an attempt to evaluate teratogenic risk and in being
able to counsel effectively pregnant women exposed to pharmaceuticals.
2 Confounding Effects
Hence, the safety of drugs in pregnancy is almost entirely dependent on observa-

tional studies. Such studies, either prospective or retrospective cohorts, or case
control studies, involve collecting exposed and unexposed mothers (in cohort
studies), or infants with or without a given adverse event (in case-control studies).
These designs are subject to a large list of potential pitfalls; leaving them
unrecognized can lead to serious error in interpretations, as will be documented

herein.
The following are major sources of confounders and bias typical of observa-
tional studies.
2.1 Sample Size
Major birth defects are relatively rare, accounting on average to 1–3% of all births.
Hence large numbers are needed to show excess risk at alpha of 5% and beta of
80%. For example, 800 women are needed in a two arm study to show a doubling
of major malformations. The situation is much more complex in trying to quantify
major malformation (rather than all of them lumped together). For example, neural
tube defects occur in 1:1,000 births. Valproic acid increases that risk to 20:1,000.
Hence, hundreds of cases of maternal exposure to valproic acid during the first
28 days post conception may be needed to be able to document a difference from
baseline risk.
The vast majority of cohort studies published to date are underpowered to
show significant differences, a problem acknowledged by many of their authors.
A common way to overcome this issue is synthesizing similar studies into meta-
analysis, thus gaining a large sample size. As would be expected, lumping studies
together into meta-analysis introduces its own set of issues, some of which will be
addressed herein, including heterogeneity among studies, not being able to control
for confounders, and under-reporting of negative studies [i.e., those showing no
excess in adverse effects (Einarson et al. 1988)].
2.2 Bias by Indication
Women taking medications during and after conception often suffer from con-
ditions which, per se, may affect pregnancy outcome. For example, chronic hyper-
tension in pregnancy is associated with high risk of prematurity, unrelated to which
drug is used to treat the hypertension. We have recently shown that hypertensive
women have above 20% rates of prematurity in their offspring, whether treated with
labetolol or methyldopa, as compared to only 4% among healthy controls (Nulman
et al. 2010).
This source of bias can often be corrected by having, in addition to the drug
exposed group and healthy control groups, an additional group with the same
condition, treated with another pharmaceutical.
290 G. Koren
2.3 Time of Enrollment as a Bias
Prospective cohort studies pride themselves that by enrolling women in early

pregnancy, (i.e., before the outcome of pregnancy is known), they avoid the serious
bias of retrospective data collection. However, most miscarriages occur during the
first trimester of pregnancy. Hence, the later one recruits pregnant women, the less
likely they are to find cases of miscarriage. For example: if a group of women
exposed to paroxetine is recruited at 5 weeks of gestation and followed up, whereas
women exposed to other drugs recruited at 10 weeks of gestation, clearly there is
a chance for more miscarriages to be detected and reported in the paroxetine cohort.
There are two possible ways to overcome this type of bias:
1. By matching women in all arms of the study to be recruited in the same week of
gestation.
2. By post-hoc statistical adjustment for the time of enrollment.
2.4 Bias in Retrospective Studies
A large number of studies attempting to associate pharmaceutical exposure with

malformation rates are retrospective in nature, that is, the cases were collected after
pregnancy outcome is known. It is conceivable that women having malformed
children would more likely report them to drug companies or to regulatory agen-
cies. This hypothesis was proven in 1999 by Bar Oz and colleagues, who compared
a retrospective registry to a prospective one of the same drug (itraconazole) (Bar-Oz
et al. 1999).
In the prospectively collected group there was a 3% malformation rate sug-
gesting no increased teratogenic risk. In contrast, there was a more than fourfold
a (14%) malformation rate in the retrospectively ascertained cohort (Bar-Oz et al.
1999). Acknowledging this serious source of bias is critical. Yet, there is also
a “positive” message here: If, despite this bias, a retrospectively collected cohort
does not exhibit a higher malformation rate than expected in the general population,
it is conceivable that the drug is safe.
2.5 Recall Bias
Case-control studies typically enroll children with a specific malformation (e.g.,

spina bifida) and a healthy control group, and ask the mothers what pharmaceutical
products they had used during pregnancy, and specifically, during the first trimester
of pregnancy.
It has been argued that mothers of malformed children may have a different
pattern of recall than mothers of healthy children. Specifically, the malformation
may facilitate memory in an attempt to find a pregnancy-related cause. This source

of bias can be remedied by collecting group of children with a different malforma-
tion, unrelated to the hypothesis in question. For example, Pastuszak et al.
ascertained that Brazilian women giving birth to children with the M€obius sequence
had a much higher likelihood to use misoprostol in an attempt to terminate preg-
nancy than women giving birth to children with spina bifida (Pastuszak et al. 1988).
A typical prospective cohort study in pregnancy recruits women exposed to
pharmaceuticals before the outcome of pregnancy is known, and this is why the
term “prospective” is used. However, at a later follow-up, women are asked about
their health after the first interview and up till now. It is important to recognize that
this part of the study is retrospective and hence open to recall bias. This becomes
very important in trying to correlate, for example, the severity of the disease with
outcome.
One of the most cited advantages of prescription databases linked to neonatal
registries is that the dose of drug and length of treatment are not dependent on
maternal recall. The trade-off is that prescription record does not yet prove that the
pharmaceutical was taken by the pregnant mother. The seriousness of this source of
error was acutely exhibited when Jick and colleagues correlated maternal prescrip-
tion of spermicides with congenital malformation (Jick et al. 1981). It was argued
that prescription of spermicides before conception did not yet mean that the women
took them. Indeed, in a follow-up study of the malformed cases in this study,
Watkins showed that almost none of the mothers took spermicides into pregnancy
(Watkins 1986).
2.6 Bias in Not Including Elective Abortion Data
Many administrative database studies do not have data on findings among women
who had elected to have an abortion. Rather, they report of “liveborn infants.” Levy
and colleagues hypothesized that a significant number of elective abortions are
performed to date due to a major malformation diagnosed in utero. By not having
such data, one takes the risk of missing a signal. Using the example of antifolates in
pregnancy, known to increase the risk of neural tube defects, Levy et al. have
showed that in their cohort such an association was apparent only when elective
abortion data were considered too, but not when only live births were counted
(Levy et al. 2009).
2.7 Bias in Retrospective Ascertainment of Maternal Lifestyle
Alcohol, maternal smoking and other drugs of abuse may increase fetal risks, both
in terms of birth defects, as well as in terms of prematurity, intrauterine growth
retardation, miscarriage, still birth, and developmental teratogenicity.
292 G. Koren
Due to shame, guilt, and fear of losing custody of a child, it is conceivable that
women experiencing adverse effects in their offspring may underreport on drugs
and alcohol abuse. This hypothesis was proven by Wong et al., studying a cohort of
women who were counseled by a teratology information service during the first
trimester of pregnancy. In particular, their reports on cigarette smoking were
probed. When re-interviewed after the birth of the child, women who had healthy
babies reported again very similar patterns of smoking as they had done originally.
In contrast, women giving birth to offspring experiencing adverse outcome tended
to minimize the numbers of cigarettes consumed when compared to their original
reports (Wong and Koren 2001). This type of bias may seriously impair studies on
the effect of alcohol, cigarettes, and drugs of abuse by introducing misclassification,
i.e., women who smoked are erroneously classified as non smokers.
2.8 Bias Against the Null Hypothesis
Bias against the null hypothesis occurs when “positive” studies (e.g., showing
a drug to be teratogenic) are more likely to be submitted for scientific meetings
and journals, to be presented, published, and publicized than “negative” studies
(e.g., those suggesting the pharmaceutical is safe). The seriousness and pervasive-
ness of this bias has been shown at each step of the act of reporting results.
Investigating the fate of studies submitted to the Oxford University ethics
committee, Easterbrook and colleagues have shown that “negative” studies were
significantly less likely to be submitted or published in peer reviewed journals. Of
interest, this was not only due to the journals rejecting them more (Easterbrook
et al. 1991), but also due to the perception of the investigators that their studies are
less likely to be accepted. More related to adverse pregnancy outcome, we have
shown that abstracts failing to identify reproductive risks of cocaine were less likely
to be accepted by the Society for Pediatric Research than “positive” studies, despite
the negative studies being overall of better quality (Koren et al. 1989).
The bias against the null is further augmented by the lay media, which tends to
publicize significantly more “positive” studies than “negative” ones. This grim
reality was documented unequivocally in the case of two studies published back
to back by the Journal of the American Medical Association. In 1992, JAMA
published two studies dealing with the risk of radioactive exposure (Koren and
Klein 1991). A study on the fate of several thousand workers in Oakridge develop-
ing the American Atomic bomb in the 1940s has shown increased risk of leukemia.
In contrast, a study investigating whether residing near nuclear energy plants failed
to show excess of cases of cancer. Despite similar exposure in the journal, the
“positive” study was cited by the lay media significantly more often (Koren and
Klein 1991).
It is now evident that the bias against the null hypothesis is pervasive and
encompasses every step of the production of new knowledge, starting with the
authors not believing in their chances of publishing, continuing with medical

meetings not selecting them for presentation.
Because of the confidential nature of the editorial process of selecting peer
review papers for publication, it is impossible to verify whether the editorial
process also results in bias against the null hypothesis.
3 Conclusions
Due to the inability to collect safety fetal data of sufficiently high quality, assess-
ment of pharmaceutical molecules is one of the most challenging areas of
pharmacoepidemiology.
It will be important to continue and refine the methodology involved in this quest
for critical data, to avoid misinformation, which may lead to both unwarranted
anxiety, as well as unjustified sense of safety.
It is critical to remember that physicians and patients, alarmed by an impression
or perception of teratogenic risk may take extreme measures of either terminating
an otherwise wanted pregnancy (Koren and Pastuszak 1990), or avoiding treatment
even in life-threatening situations (Cohen et al. 2006). We must facilitate a new
climate, where this practice is evidence based.
References
Bar-Oz B, Moretti ME, Mareels G, Van Tittelboom T, Koren G (1999) Reporting bias in
retrospective ascertainment of drug-induced embryopathy. Lancet 354:1700–1701
Cohen LS, Altshuler LL, Harlow BL, Nonacs R, Newport DJ, Viguera AC, Suri R, Burt VK,
Hendrick V, Reminick AM, Loughead A, Vitonis AF, Stowe ZN (2006) Relapse of major
depression during pregnancy in women who maintain or discontinue antidepressant treatment.
JAMA 295:499–507
Easterbrook PJ, Berlin JA, Gopalan R, Matthews DR (1991) Publication bias in clinical research.
Lancet 337:867–872
Einarson TR, Leeder SJ, Koren G (1988) A method for meta-analysis of epidemiological studies.
Drug Intell Clin Pharm 22:813–823
Jick H, Walker AM, Rothman KJ, Hunter JR, Holmes LB, Watkins RN, D’Ewart DC, Danford A,
Madsen S (1981) Vaginal spermicides and congenital disorders. JAMA 245:1329–1332
Koren G, Klein N (1991) Bias against negative studies in newspaper reports of medical research.
JAMA 266:1824–1826
Koren G, Pastuszak A (1990) Prevention of unnecessary pregnancy terminations by counseling
women on drug, chemical, and radiation exposure during the first trimester. Teratology
41:657–661
Koren G, Graham K, Shear H, Einarson T (1989) Bias against the null hypothesis: the reproductive
hazards of cocaine. Lancet 2:1440–1442
Koren G, Pastuszak A, Ito S (1998) Drugs in pregnancy. N Engl J Med 338:1128–1137
Levy A, Matok I, Gorodischer R, Koren G (2009) Bias toward the null hypothesis by not including
abortion data. European Society of Development Pediatric and Perin Pharmacology, France
294 G. Koren
Nulman L, Chan WS, Koren G, Bamora M, Rezvanl M, Knittel-Keren D (2010) Neurocognitive

development of children following in-utero exposure to labetalol for maternal hypertension
a cohort study using a prospectively collected database. Hypertens Pregnancy 28(3):271–83
Pastuszak AL, Sch€uler L, Speck-Martins CE, Coelho KE, Cordello SM, Vargas F, Brunoni D,
Schwarz IV, Larrandaburu M, Safattle H, Meloni VF, Koren G (1988) Use of misoprostol
during pregnancy and M€ obius’ syndrome in infants. N Engl J Med 338:1881–1885
Watkins RN (1986) Vaginal spermicides and congenital disorders: the validity of a study. JAMA
256:3095–3096
Wong M, Koren G (2001) Bias in maternal reports of smoking during pregnancy associated with
fetal distress. Can J Public Health 92:109–112
Antiepileptic Treatment in Pregnant Women:
Morphological and Behavioural Effects
Torbj€
orn Tomson and Dina Battino
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 296
2 Teratogenic Effects of AEDs: Methodological Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 297
3 Growth Retardation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
4 Minor Anomalies and Dysmorphisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 299
5 Major Congenital Malformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
5.1 Overall Malformation Rates with AEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 300
5.2 Specific Malformations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 301
5.3 Comparative Malformation Rates with Different AEDs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 302
6 Postnatal Cognitive Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 306
7 Dose-Dependency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
8 Mechanisms of Teratogenesis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 308
9 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 310
Abstract It is well established that children exposed to antiepileptic drugs

(AEDs) in utero have an increased risk of adverse pregnancy outcomes including
foetal growth retardation, major congenital malformations and impaired postnatal
cognitive development. However, due to the significant maternal and foetal risks
associated with uncontrolled epileptic seizures, AED treatment is generally
maintained during pregnancy in the majority of women with active epilepsy.
The prevalence of major malformations in children exposed to AEDs has ranged
from 4 to 10%, 2–4 times higher than in the general population. More recent studies
T. Tomson (*)
Department of Clinical Neuroscience, Karolinska Institutet, S-171 76 Stockholm, Sweden
e-mail: torbjorn.tomson@karolinska.se
D. Battino
Department of Neurophysiopathology and Epilepsy Centre, IRCCS Foundation Carlo Besta,
Neurological Institute, Milan, Italy

296 T. Tomson and D. Battino
suggest a smaller increase in malformation rates. Malformation rates have con-

sistently been higher in association with exposure to valproate than with carbamaz-
epine and lamotrigine. Some prospective cohort studies also indicate reduced
cognitive outcome in children exposed to valproate compared to carbamazepine
and possibly lamotrigine. Information on pregnancy outcomes with newer genera-
tion AEDs other than lamotrigine are still insufficient.
Keywords Antiepileptic drugs • Teratogenicity • Congenital malformations •

Pregnancy • Epilepsy
1 Introduction
The first report on possible human teratogenic effects of antiepileptic drugs (AEDs)
was published more than 40 years ago (Meadows 1968). Meadows reported six
children with orofacial clefts, some with additional abnormalities of the heart and
face, all of whom had been exposed to AEDs in utero. Treatment was mainly
different combinations of phenobarbital, phenytoin and primidone. In a subsequent
retrospective survey of more than 400 pregnancies with epilepsy Speidel and
Meadow (Speidel and Meadow 1972) found a twofold increase in malformation
rate among children of mothers with epilepsy exposed to AEDs. A specific associ-
ation between trimethadione and a very high prevalence of malformations was also
reported early (German et al. 1970). Since then numerous studies with different
methodologies have reported increased rates of teratogenic outcomes in mothers
with epilepsy (Harden et al. 2009; Meador et al. 2008; Tomson and Battino 2005;
Tomson and Hiilesmaa 2007). These adverse outcomes include major congenital
malformations, minor anomalies and dysmorphism, growth retardation, and
impaired cognitive development. In addition to trimethadione, all of the major
old generation AEDs such as phenobarbital, phenytoin, valproate and carbamaze-
pine, have been reported to be associated with increased risks for major congenital
malformations, while less is known about the teratogenic potential of the newer
generation AEDs that have been introduced to the market during the last 20 years.
Epilepsy is a condition characterised by the occurrence of recurrent epileptic
seizures, with potentially serious consequences. Uncontrolled seizures significantly
affect the quality of life of the patient with epilepsy, and major convulsive seizures
could be harmful and occasionally even fatal (Tomson et al. 2004a). In addition to
these harmful effects on the person with epilepsy, maternal seizures during preg-
nancy may also adversely affect the foetus (Tomson and Hiilesmaa 2007). Hence,
the potential adverse outcomes in the offspring due to maternal use of AEDs need to
be weighed and balanced against the risks associated with the underlying disease
itself. In epilepsy, the maternal and foetal risks with uncontrolled major convulsive
seizures are generally considered to outweigh the teratogenic risks with AEDs.
Treatment is therefore maintained also during pregnancy in women with active
Antiepileptic Treatment in Pregnant Women: Morphological and Behavioural Effects 297
epilepsy aiming at complete control of generalized tonic-clonic seizures (Tomson

and Hiilesmaa 2007).
Women with epilepsy have been estimated to account for 0.3% up to 0.7% of all
pregnancies (Gaily 1991; Viinikainen et al. 2006). The proportion of pregnancies
with exposure to AEDs is probably even higher considering the increasing use of
AEDs for other indications than epilepsy (Spina and Perugi 2004). The vast
majority of these women will have uneventful pregnancies and give birth to
perfectly normal children. However, the medical management during pregnancy
is a matter of special concern since maternal epilepsy and AED treatment are
associated with an increased risk for an abnormal pregnancy outcome.
2 Teratogenic Effects of AEDs: Methodological Issues
Many different methods have been used to assess the foetal risks associated with
exposure to AEDs. The first years after the initial report on possible teratogenic
effects of AEDs saw many publications of case-series of adverse pregnancy
outcomes collected in individual centres or regions. A slightly more systematic
method is spontaneous reporting of pregnancy outcome to the manufacturers,
to drug agencies or surveillance programmes. Such methods can be useful in
providing signals. However, reporting is selective, and since information on the
denominator (total number of pregnancies exposed to the drug) is missing, these
methods cannot be used for a proper risk assessment.
Case–control designs are generally considered useful for assessment of uncom-
mon outcomes, such as birth defects. Cases with malformations are compared to
controls regarding exposure to AEDs in foetal life. The method has been used
to study the association between some specific malformations and exposure to
individual AEDs, e.g. neural tube defects and exposure to valproate and oral clefts
and lamotrigine. Case–control studies have also been utilised to analyse exposure
to different AEDs and congenital abnormalities in general (Kjaer et al. 2007).
A drawback of case–control studies is the risk of recall bias. Mothers of children
with malformations are more likely to report drug intake during pregnancy.
Other studies have utilised existing general registries. Information on exposure
could be obtained from a national drug prescription database (Artama et al. 2005) or
from other registries that systematically and prospectively obtain information on
drug intake in early pregnancy. The Swedish and Norwegian Medical Birth
Registries are examples of the latter. These can be crosslink with registries of
birth defects to assess the association between use of AEDs in early pregnancy
and adverse outcome (Veiby et al. 2009; Wide et al. 2004). Such registries can have
the advantage of recording exposure before pregnancy outcome is known and in
addition being population-based, nationwide and thus representative. Contrarily,
they often lack details on important information such as drug dosage, indication for
treatment and classification of epilepsy, seizure control during pregnancy and on
other factors that could contribute to the outcome. Furthermore, the teratogenic
outcome might not be classified according to uniform criteria and the assessor of the
child might be influenced by information on drug intake during pregnancy.
Another common approach is cohort studies of pregnancies in women with
epilepsy. Retrospective cohort studies (where women are included at a time when
pregnancy outcome might be known) are associated with a risk of selection bias.
This is avoided in prospective studies where women ideally are identified and
enrolled in early pregnancy before any information on pregnancy outcome is
known. Such studies have traditionally often been hospital based and many studies
based on cohorts from single hospitals or epilepsy centres or from several
collaborating clinics were published in the 1980s and 1990s (Tomson et al.
2004b). Additional advantages with such prospective cohort studies is that they
usually have a reliable classification and details on the mothers’ epilepsy, the course
of the epilepsy during pregnancy and on other potential risk factors. The major
disadvantage is that they represent selected epilepsy populations, probably more
severe cases under specialist care. A further major limitation has been in the
number of included pregnancies, often a few hundred and at best a thousand
pregnancies (Tomson and Battino 2005).
Special types of cohort studies, antiepileptic drugs and pregnancy registries,
were established in the late 1990s and have thus now been operational for more than
a decade (Tomson et al. 2010). These registries are prospective observational
studies enrolling women with epilepsy early in pregnancy collecting information
on drug exposure and other potential risk factors before outcome of the pregnancy
is known. Women are followed throughout pregnancy and the outcome in terms of
occurrence of birth defects in the offspring is recorded. The advantage of such
studies is that they may collect high numbers of pregnancies, the type of drug
exposure is recorded in an unbiased way without prior knowledge of teratogenic
outcome, and detailed data on other relevant patient characteristics could be
obtained. They share the limitations of many previous cohort studies in being
based on selected patients, which hampers the possibilities to generalize from the
results and although they share many methodological features, there are also
significant differences between them (Tomson et al. 2010).
The aforementioned studies are designed primarily to evaluate the risk of major
congenital malformations. Assessment of postnatal cognitive development poses
further difficulties and challenges. An extended follow-up is necessary. By this,
however, environmental factors such as psycho-social factors, including maternal
education, cognitive status and epilepsy may all affect the child’s performance. The
assessor needs to be blinded and appropriate controls included.
Even results of prospective studies of teratogenic effects of AEDs may be
difficult to interpret. For obvious reasons, women considering pregnancy have not
been randomised to different types of treatment. The selection of a particular
treatment depends on individual environmental and genetic factors that could be
linked to the risk of adverse pregnancy outcome. An association between exposure
to a certain AED and occurrence of adverse pregnancy outcome in an observational
study is thus not evidence of a causal relationship. The impact of possible
confounders, such as type of epilepsy, seizure frequency, family history of birth
defects and exposure to additional risk factors needs to be assessed, which requires
large sample sizes. It is thus important to pay attention to methodological issues
such as statistical power, reliability of collected data, and attempts to control for
appropriate confounding factors in the analyses, rather than to just compare rates
of adverse pregnancy outcome in published studies.
3 Growth Retardation
Reduced birth weight, body length and head circumference in the offspring of
women treated with phenytoin was reported already in the 1970s (Hanson et al.
1976). Such reductions in body dimensions were confirmed in subsequent studies of
larger cohorts (Battino et al. 1992, 1999; Dessens et al. 2001; Hiilesmaa et al. 1981;
Wide et al. 2000). In general, more pronounced effects were found in infants
exposed to polytherapy, whereas the association between reduced body dimensions
and specific AEDs in monotherapy varies. Phenobarbital and primidone have been
implicated, whereas others have reported carbamazepine to be most strongly
associated with small head circumference. A population-based Swedish study
spanning 25 years, found a clear trend towards normalization of the head circum-
ference in parallel with a shift from polytherapy towards monotherapy despite an
increasing use of carbamazepine (Wide et al. 2000). Other more recent studies also
suggest that, with present treatment strategies, microcephaly may no longer be
more common among infants of mothers treated for epilepsy during pregnancy
(Choulika et al. 1999). A very recent populations-based nationwide Norwegian
study found low birth weight, small for gestational age, and small head circumfer-
ence to be significantly more common in infants of mothers with epilepsy compared
to the general population (Veiby et al. 2009). However, small for gestational age
was more common in the offspring of mothers with epilepsy whether the mothers
were taking AEDs or not.
A committee of the American Academy of Neurology and the American Epi-
lepsy Society recently reassessed the evidence related to the care of women with
epilepsy during pregnancy (Harden et al. 2009). The committee concluded that
neonates of women with epilepsy taking AEDs probably have an increased risk of
small for gestational age about twice the expected rate.
4 Minor Anomalies and Dysmorphisms
Minor anomalies are structural variations without medical, surgical or cosmetic

importance. Discrete minor anomalies are frequently found in normal infants, but
combinations of several anomalies can form a pattern, a dysmorphic syndrome,
which may indicate a more severe underlying dysfunction. The term “foetal anti-
convulsant syndrome” has been used to describe an AED-associated embryopathy
variably characterised by microcephaly, growth retardation, hypertelorism, depressed

nasal bridge, low set ears, micrognathia and distal digital hypoplasia, other
anomalies, and sometimes developmental delay (Dean et al. 2002; Holmes et al.
2001; Moore et al. 2000). More distinctive phenotypes have also been claimed to
be associated with specific AEDs, most notably phenytoin, carbamazepine and
valproate. Valproate exposure has been claimed to cause a somewhat different
dysmorphic syndrome characterised by thin arched eyebrows with medial defi-
ciency, broad nasal bridge, short anteverted nose, and a smooth long filtrum with
thin upper lip. Such features have been suggested to be associated with, and
indicative of, impaired cognitive development (Dean et al. 2002; Kini et al.
2006). The overlap in the various dysmorphisms is considerable and their drug
specificity has therefore been questioned as has their predictive significance vs.
cognitive development (Perucca and Tomson 2006). In addition, the pathogenesis is
still somewhat controversial. Gaily et al. (1988) attributed most of the minor
anomalies to genetic factors rather than drug exposure, although most studies
suggest that there is an association between minor anomalies and exposure to
AEDs. Indeed one study of infants of untreated mother with epilepsy failed to
find any features of the foetal antiepileptic drug syndrome in the offspring (Holmes
et al. 2000). It should, however, be underlined that minor anomalies are much more
difficult to assess objectively than major malformations, and that the incidence
of minor anomalies in exposed infants varies markedly between studies.
5 Major Congenital Malformations
5.1 Overall Malformation Rates with AEDs
Major congenital malformations are commonly defined as a structural abnormality

with surgical, medical or cosmetic importance. Numerous studies from the 1980s
and 1990s have confirmed increased rates of birth defects in children of mothers
with epilepsy. The prevalence of major congenital malformations in children
exposed to AEDs has ranged from 4 to 10%, corresponding to a two- to fourfold
increase from the expected in the general population (Harden et al. 2009; Meador
et al. 2008; Tomson and Battino 2005, 2009; Tomson and Hiilesmaa 2007). A few
more recent studies, however, have not demonstrated increased risks in infants
exposed to AEDs in utero compared to offspring of women with epilepsy not taking
AEDs (Morrow et al. 2006; Veiby et al. 2009). In a prospective observational study
from the UK, the relative risk of major congenital malformations among children of
mothers with epilepsy taking AEDs during pregnancy vs. women with untreated
epilepsy was 1.19 (0.59–2.40) (Morrow et al. 2006). In a nationwide population-
based Norwegian registry study, the frequency of major malformations was 3.3% in
children of mothers with treated epilepsy, not significantly different from the 2.5%
among controls in the general population (Veiby et al. 2009).
Much of the variation in reported outcomes could be explained by differences in

study methodology including study populations, in selection of control populations
and in criteria for malformations. A possible decrease in recent years in the
prevalence of malformations in offspring of women with epilepsy might also be
related to changes in treatment strategies. It is possible that more frequent use of
AED monotherapy as opposed to polytherapy, use of lower doses, changes in AED
preferences, and pre-conceptional counselling has contributed to a more optimal
management with reduced foetal risks. Nevertheless, it is still debated whether the
usually reported increase in malformation rates is entirely caused by AEDs or if to
some extent this could be linked to the underlying epilepsy disorder, or to seizures.
The available data, however, strongly suggest that AED exposure is the major
factor. In 26 cohort studies that included pregnancies of women with treated as well
as untreated epilepsy, the average malformation rate among children exposed to
AEDs in utero was 6.1% compared to 2.8% among children of mothers with
untreated epilepsy and 2.2% in infants of healthy controls (Tomson and Battino
2009). These observations have been confirmed in a meta-analysis of the evidence
of epilepsy per se as a teratogenic risk (Fried et al. 2004). Ten studies reporting rates
of congenital malformations in offspring of untreated women with epilepsy were
included. The malformation rate in this group was not higher than among offspring
of non-epileptic healthy controls, odds ratio (OR) 1.92 (0.92–4.00). The OR was
0.99 (0.49–2.01) after removal of some small studies likely to be affected by
publication bias.
Although obviously, untreated women with epilepsy are different in many
respects from those who are under treatment during pregnancy, the available
evidence strongly suggests that treatment is the major cause of increased risk of
adverse pregnancy outcomes. Further support for a drug effect comes from the
observation of greater risks with polytherapy compared to monotherapy with
AEDs. Polytherapy was associated with a malformation rate of 6.8 vs. 4.0% in
monotherapy in a recent pooled analysis (Tomson and Battino 2009).
5.2 Specific Malformations
The pattern of malformations associated with AEDs as a group is mostly similar

to that seen in the general population. Cardiac defects are the most common
followed by facial clefts, and hypospadia (Battino and Tomson 2007). There
may, however, be an association between certain individual AEDs and some
specific malformations. Neural tube defects and hypospadia are more common
among offspring of mothers who used valproate during pregnancy (Morrow et al.
2006; Samrén et al. 1999), the risk of neural tube defects in association with
valproate has been estimated to 1–2% (Lindhout and Schmidt 1986). An increased
risk of neural tube defects of 0.5–1% has also been reported after carbamazepine
exposure (Kallen 1994; Rosa 1991). Valproate has also been associated with facial
clefts (Morrow et al. 2006) and phenytoin and carbamazepine with cleft palate
(Puho et al. 2007). Recent data from the North American AED Pregnancy Registry
suggested a tenfold increase in risk of oral clefts among lamotrigine exposed infants
(Holmes et al. 2008a), but this specific association has not been confirmed in other
registries (Dolk et al. 2008; Holmes et al. 2008a). Exposure to phenobarbital has
been suggested to increase the risk of cardiac malformations (Canger et al. 1999).
5.3 Comparative Malformation Rates with Different AEDs
For reasons discussed above, women with active epilepsy will need continued
treatment throughout pregnancy. The relative safety during pregnancy is therefore
a major criterion for selection of an AED for a woman with epilepsy who is of child-
bearing potential. Large studies are needed to draw conclusions on the relative
teratogenic potential of different AEDs as the prevalence of birth defects with
AEDs fortunately is no more than 4–10%. However, surprisingly few studies in
the past have comprised more than 500 pregnancies in total. Clearly much larger
cohorts are needed to permit a meaningful assessment of individual AEDs. During
the last decade, some different strategies have been applied to achieve this.
One method, which has been used in the Nordic countries, is to utilise different
existing national registries and databases for the purpose of assessing the safety of
AED use in pregnancy. One example is the Swedish Medical Birth Registry, a
nationwide population-based health registry compiled from antenatal maternal health
clinic records, and those of the delivery and maternity wards. Drug exposure is
recorded at the first visit to the maternity health clinics (typically gestational week
9). Pregnancy outcome is assessed based on registries of birth defects. A report from
this registry was based on 1,398 pregnancies with exposure to AEDs (Wide et al.
2004). The odds ratio (OR) for having a malformation in the AED-exposed offspring,
compared with the expected estimate from all infants born, was 1.86 (1.42–2.44)
overall. OR in monotherapy exposed was 1.61 (1.18–2.19), and in polytherapy 4.20
(2.42–7.49). The OR was higher after exposure to valproate monotherapy compared
with carbamazepine monotherapy 2.59 (1.43–4.68).
Another nationwide population-based study utilized the Finnish drug prescrip-
tion database and the National Medical Birth Registry to identify all women who
were prescribed AEDs during pregnancy (Artama et al. 2005), including 1,411
pregnancies with AED exposure. Congenital malformations were more common
among offspring of these women (4.6%) than among offspring of untreated patients
with epilepsy (2.8%). Compared with untreated patients, the risk of malformations
was higher in foetuses exposed to valproate monotherapy (malformation rate
10.7%; OR ¼ 4.18; 2.31–7.57) or valproate as part of polytherapy (malformation
rate 9.2%; OR ¼ 3.54; 1.42–8.11). In contrast, the risk of malformations was not
elevated in association with exposure to carbamazepine, oxcarbazepine, or phenyt-
oin monotherapy.
A third example is a recent study from Norway. The nationwide compulsory
Medical Birth Registry of Norway was surveyed from 1999 to 2005 (Veiby et al.
2009). A total of 961 pregnancies with AED exposure were identified. An increased
risk for major congenital malformations compared to unexposed could be
demonstrated only for valproate monotherapy (5.6 vs. 2.5% in the general popula-
tion) and AED polytherapy (6.1%).
The advantage of these studies is that they are population based and the results
are likely to be representative. However, they lack detail concerning other potential
risk factors, e.g. the indication for treatment and type of epilepsy, seizure control
during pregnancy, AED dosage and other. Pregnancies ending in elective abortions
are also not included even if the indication was foetal abnormalities. Most impor-
tantly, although nationwide, the number of included pregnancies on different
specific AEDs is too small to permit a more precise comparison of their teratogenic
potential.
In order to facilitate enrolment of greater numbers of pregnancies with AED
exposure, and thus more meaningful comparisons, different groups established
specific Epilepsy and Pregnancy Registries in the late 1990s (Tomson et al.
2010). Some were set up by pharmaceutical companies and collect data on the
manufacturers’ own product (e.g. GlaxoSmithKline’s International Lamotrigine
Registry) (Cunnington et al. 2007). Others have been established by independent
research groups and include information on all AED exposures. These are national,
regional (e.g. Australia, UK, North America, Kerala, India) or broadly international
(European and International Registry of Antiepileptic Drugs in Pregnancy,
EURAP). Many of the registries have now been operational for more than
10 years and are beginning to release results.
Malformation rates reported from pregnancy registries and from some other
larger and contemporary studies are presented for the five most frequently used
AEDs (valproate, carbamazepine, lamotrigine, phenobarbital and phenytoin) in
Table 1.
In the absence of a comparator, the results from the company-sponsored
registries are difficult to interpret. However, GlaxoSmithKline’s International
Lamotrigine Pregnancy Registry reported a malformation rate of 2.9% based on
802 monotherapy exposures (Cunnington et al. 2007).
The largest independent AED and pregnancy registries are The North American
Antiepileptic Drugs and Pregnancy Registry (NAAPR), the United Kingdom Epi-
lepsy and Pregnancy Register, and EURAP, an international registry enrolling
pregnancies from more than 40 countries, in Europe, Australia, Asia, Oceania and
South America (Tomson et al. 2010). These registries have enrolled 6,000–14,000
pregnancies and two of them, NAAPR and the UK register, have published results
on teratogenic outcome. These three registries are slightly different in their scope
and differ significantly in their methodologies, which should be kept in mind when
malformation rates are compared across the registries.
NAAPR has reported increased malformation rates in comparison with the
general population with phenobarbital monotherapy (6.5%), relative risk (RR) 4.2
(1.5–9.4) (Holmes et al. 2004), and valproate (10.7%) RR 7.3 (4.4–12.2)
(Wyszynski et al. 2005). The malformation rate was 2.8% with lamotrigine
monotherapy (Holmes et al. 2008a), 2.5% (n ¼ 873) with carbamazepine and
Table 1 Rates of malformations,% and (number of monotherapy exposures) with antiepileptic

drugs in monotherapy in some major studies
Study/registry Valproate Carbamazepine Lamotrigine Phenobarbital Phenytoin
Samrén et al. (1997) 8.7% (184) 7.9% (280) 10.4% (48) 6.4% (141)
Samrén et al. (1999) 5.7% (158) 3.7% (376) 2.9% (172) 0.7% (151)
Kaneko et al. (1999) 11.1% (81) 5.7% (158) 5.1% (79) 9.1% (132)
GlaxoSmithKline
(Cunnington et al.
2007) 2.9% (802)
Finnish Drug
prescription
(Artama et al.
2005) 10.6% (263) 2.7% (805)
Swedish Medical
Birth Registry
(http://www.
janusinfo.org/) 7.7% (507) 5.4% (1,199) 4.9% (400) 7.6% (145)
UK Register (Morrow
2007, data on file
of the UK Epilepsy
Pregnancy
Registry, personal
communication) 6.2% (715) 2.2% (900) 3.2% (647) 3.7% (82)
North American
Registry
(Hernandez-Diaz
et al. 2007; Holmes
et al. 2004, 2008a,
b; Wyszynski et al.
2005) 10.7% (149) 2.5% (873) 2.8% (684) 6.5% (77) 2.6% (390)
Australian Register
(Vajda et al. 2007) 13.3% (166) 3.0% (234) 1.4% (146) 3.2% (31)
Norwegian Birth
Registry (Veiby
et al. 2009) 5.9% (204) 2.6% (454) 2.7% (260) 0% (14) 0% (19)
2.6% (n ¼ 390) with phenytoin monotherapy (Hernandez-Diaz et al. 2007), not

significantly increased from the background rate of 1.6%.
The UK register published their first report based on 3,607 cases (Morrow et al.
2006). The rate of major congenital malformations for pregnancies exposed to
valproate monotherapy was 6.2% (4.6–8.2%) compared with 2.2% (1.4–3.4%) for
carbamazepine. The malformation rate with lamotrigine monotherapy was 3.2%
(2.1–4.9%) based on 647 pregnancies. Interestingly, the malformation rate in
offspring of 227 untreated women with epilepsy was 3.5% (1.8–6.8%), very similar
to the 3.7% (3.0–4.5%) among the monotherapy exposures in general (n ¼ 2,468).
It is evident from Table 1 that malformation rates across studies vary consider-
ably for the same AED in monotherapy. Carbamazepine exposure was associated
with rates ranging from 2.2 to 7.9%, lamotrigine from 1.4 to 4.9%, phenytoin from
0.7 to 9.1%, and valproate from 5.7 to 13.3% (Table 1). The wide ranges in
malformation rates reflect differences in study populations, criteria and methodol-
ogy. Prevalences of malformations with different AEDs should therefore not be
compared across studies. However, there appears to be a consistent pattern within
studies with higher rates with valproate and lower rates with carbamazepine and
lamotrigine (Table 1). Even within-study comparisons should be made with caution
considering the possible effects of confounding factors.
There is very limited published data on pregnancy outcome with other new
generation AEDs than lamotrigine. Malformation rates in reports based on prospec-
tive pregnancies with monotherapy exposure to newer generation AEDs other than
lamotrigine, such as gabapentin, topiramate, levetiracetam, oxcarbazepine and
zonisamide, are shown in Table 2. Even when pregnancies from all available
studies are added up, the total number of monotherapy exposures for each of
gabapentin, topiramate, levetiracetam, oxcarbazepine is limited to approximately
250–300 pregnancies, and much less for zonisamide. Clearly these numbers are too
small for a reliable assessment of the risks.
In their recent evidence-based review, the American Academy of Neurology and
the American Epilepsy Society Committee concluded that it is highly probable that
valproate exposure during the first trimester is associated with higher risk of major
congenital malformations compared to taking carbamazepine, and possibly
Table 2 Monotherapy exposures to some newer generation antiepileptic drugs in different

published studies, number of exposures (number of pregnancies with major malformations)
References GBP TPM LEV OXC ZNS
Kondo et al. (1996) 4 (0)
Samrén et al. (1999) 2 (0)
Fonager et al. (2000) 1 (0) 14 (0)
Hvas et al. (2000) 7 (0)
Long (2003) 3 (0)
Montouris (2003) 16 (1)
Kaaja et al. (2003) 9 (1)
Meischenguiser et al. (2004) 35 (0)
Swedish Medical Birth Registry (http://www.
janusinfo.org/) 68(5) 4 (0)
Artama et al. (2005) 99 (1)
UK Registry 2007 (Hunt et al. 2006; Hunt et al.
2008; Morrow 2007, data on file of the UK
Epilepsy Pregnancy Registry, personal
communication) 31(1) 42(1) 39(0)
Ornoy et al. (2008) 29(1)
Ten Berg et al. (2005) 11 (0)
Holmes et al. (2008a, b) 127(1) 197(8) 197(4) 121(2)
Veiby (2010, personal communication) 7(0) 16(1) 15(1) 30(1)
TOTAL 250 (8) 284(11) 265 (5) 321(5) 4 (0)
compared to phenytoin or lamotrigine (Harden et al. 2009). Other newer generation

AEDs are not mentioned in this report.
6 Postnatal Cognitive Development
During the past 3 decades, several studies with different designs have aimed at
assessing whether exposure to AEDs in utero could also adversely affect the cogni-
tive development of the child after birth. Such studies are complicated to perform,
requiring long-term follow-up. But they are also difficult to interpret because of
confounding (e.g. parental cognitive function, socio-economic circumstances, mater-
nal epilepsy) and in particular since environmental factors become more important
with increasing age of the child. Few studies have been published, and mostly based
on small cohorts. Studies from the 1980s and 1990s have aimed at assessing
phenobarbital and more often phenytoin and carbamazepine, the most frequently
used AEDs at that time. A prospective population-based study from Helsinki, Finland
found no influence of AED (mainly phenytoin and carbamazepine) exposure on
global IQ (Gaily et al. 1990). Observed cognitive dysfunction was attributed to
maternal seizures and educational level of the parents rather than to the treatment.
A Swedish population-based prospective study found no difference in psychomotor
development in children exposed to carbamazepine compared with control children
of healthy mothers, but a trend for phenytoin exposed children to do slightly worse in
some tests of motor coordination (Wide et al. 2002). Scolnik et al. (1994) reported
lower global IQ in children exposed to phenytoin but not in those exposed to
carbamazepine.
A Cochrane Review from 2004 concluded that at that time there was little
evidence about which drugs carry more risks than others to the development of
children exposed (Adab et al. 2004b). Some subsequent studies, however, have
suggested that exposure to valproate might carry a particular risk of adverse
developmental effects (Adab et al. 2001; Meador et al. 2009; Vinten et al. 2005).
A retrospective survey from the UK found additional educational needs to be more
common among children that had been exposed to valproate than in those exposed
to carbamazepine or unexposed control children (Adab et al. 2001). A more detailed
investigation revealed lower verbal IQ in those exposed to valproate than in
unexposed children and children exposed to carbamazepine or phenytoin (Adab
et al. 2004a; Vinten et al. 2005). Multiple regression analysis identified exposure to
valproate, frequent tonic-clonic seizures in pregnancy and low maternal IQ to be
associated with lower verbal IQ also after adjustment for confounding factors.
Given the retrospective design, small numbers and poor participation rate, the
results need to be interpreted with some caution. However, some subsequent
prospective studies report similar observations concerning valproate. Hence, a
small population-based prospective study from Finland found a lower verbal
IQ in children exposed in utero to valproate monotherapy (n ¼ 13) and to
polytherapy in general compared with non-exposed children or children exposed

to carbamazepine (Gaily et al. 2004). However, the results were confounded by
low maternal education and polytherapy. Another small prospective population-
based Finnish study signals a similar trend for worse outcome in children exposed
to valproate but also points to the problem of confounding factors as the mothers
using valproate in pregnancy scored lower on IQ than other groups (Eriksson
et al. 2005).
A larger, prospective observational study from Kerala, India, evaluated mental
and motor development in children of mothers with epilepsy, but already at
15 months of age (Thomas et al. 2008). Children exposed to polytherapy had
lower developmental quotients than those exposed to monotherapy. Compared
with those exposed to carbamazepine monotherapy (n ¼ 101), children exposed
to valproate monotherapy (n ¼ 71) had significantly lower mental and motor
developmental quotients, whereas there was no significant difference between
children exposed to other AEDs (mainly phenobarbital or phenytoin) compared
with valproate. Of note is that this study did not analyse the possible influence of
maternal cognitive function and outcome in the children.
The first reasonably powered truly prospective study of long-term cognitive
effects of foetal exposure to AEDs recently published interim results (Meador
et al. 2009). Between 1999 and 2004, women from USA and the UK on
monotherapy with valproate, carbamazepine, lamotrigine or phenytoin were
enrolled in early pregnancy in this observational study. The primary analysis in
this study is a comparison of neurodevelopmental outcomes at 6 years of age, but
interim results at 3 years of age have been released (Meador et al. 2009). In this
carefully designed study, children exposed to valproate (n ¼ 53) on average had an
IQ score nine points lower than the score of those exposed to lamotrigine (n ¼ 84),
seven points lower than those exposed to phenytoin (n ¼ 48) and six points lower
than children exposed to carbamazepine (n ¼ 73). IQ scores did not differ signifi-
cantly among children exposed to the other three AEDs (lamotrigine, phenytoin,
carbamazepine). These differences were obtained after adjustment for maternal IQ,
infant’s gestational age and some other potential confounding factors (Meador et al.
2009). It should, however, be noted that the IQ was within the normal range also
among children exposed to valproate. There was also a significant correlation
between the valproate dose in pregnancy and the child’s IQ. In fact children
exposed to valproate doses <1,000 mg/day did not differ in IQ from those exposed
to other AEDs.
A few retrospective studies have suggested a specific association between
exposure to valproate and the risk of developing autistic disorder (Rasalam et al.
2005), but this also needs further investigations.
The Committee of American Academy of Neurology and the American Epilepsy
Society concluded that cognitive outcomes are probably reduced in children
exposed to valproate compared to carbamazepine and possible also compared
with phenytoin (Harden et al. 2009).
7 Dose-Dependency
A dose–effect relationship has so far been shown most consistently for teratogenic-
ity in association with valproate. Dosages above 800–1,000 mg/day have thus been
associated with significantly greater risks than lower dosages (Artama et al. 2005;
Kaneko et al. 1999; Morrow et al. 2006; Samrén et al. 1997, 1999; Vajda et al.
2007). Data on cognitive outcome reveal a similar pattern. The retrospective study
from Liverpool found that verbal IQ was no different from unexposed controls
among children exposed to valproate doses <800 mg/day (Vinten et al. 2005).
Likewise, the prospective NEAD study found IQ of children whose mothers took
valproate in doses <1,000 mg/day to be similar to IQs in those exposed to other
AEDs (Meador et al. 2009).
The UK Epilepsy and Pregnancy Register reported a positive dose response for
major congenital malformations also for lamotrigine. Doses above 200 mg/day
were associated with higher risks (Morrow et al. 2006). This pattern was, however,
not found in the International Lamotrigine Registry of GlaxoSmithKline, nor did
the North American pregnancy registry find lamotrigine doses to be significantly
higher in mothers to children with malformations than in mothers to healthy
children (Cunnington et al. 2007).
The American Academy of Neurology and the American Epilepsy Society
Committee concluded that there is probably a relationship between the dose of
valproate and lamotrigine and the risk of major congenital malformations (Harden
et al. 2009).
8 Mechanisms of Teratogenesis
The mechanisms for the developmental toxicity of AEDs are likely to be multiple
and also to partly vary with different AEDs. There is clearly an individual suscep-
tibility as only a fraction of those exposed to the same treatment show signs of
teratogenic effects. This is further supported by clinical observations of greater
risks of AED-related embryopathy among siblings exposed to the same drug (Malm
et al. 2002). A similar variability in the frequency and pattern of adverse pregnancy
outcomes has been related to strain differences in experimental studies in mice
(Buehler et al. 1990; Dean et al. 1999; Finnell 1991; Lindhout and Omtzigt 1992;
Raymond et al. 1995; Strickler et al. 1985; Volcik et al. 2003). The outcome likely
depends on gene–environment interactions and susceptible embryos probably carry
genetic factors determining their susceptibility to AED-induced adverse foetal
effects (Zhu et al. 2009).
A favoured hypothesis for many years suggests that the developmental toxicity of
AEDs is related to their interference with folate metabolism. Folates are co-factors
involved in the biosynthesis of nucleic acids and in the re-methylation of homocys-
teine to methionine. Many AEDs, including phenobarbital, phenytoin, primidone
and carbamazepine, are known to reduce folate levels. Some clinical studies have
reported an association between low maternal serum folate levels and risk of
malformations (Dansky et al. 1987; Ogawa et al. 1991), although this has not been
a consistent finding. In humans, extra periconceptional supplementation with folate
has been demonstrated to reduce the risk of neural tube defects and at higher doses
also the risk of recurrence in high-risk groups (MRC 1991). It is, however, important
to understand that women with epilepsy were excluded from these studies. Obser-
vational data from epilepsy and pregnancy registries have unfortunately not
demonstrated any protective effect against adverse pregnancy outcomes of peri-
conceptional folate supplementation to women with epilepsy (Morrow et al. 2009).
The 5,10 methylene tetrahydrofolate reductase (MTHFR) gene has been
suggested as one candidate to explain genetic susceptibility to folate sensitive
malformations (Dean et al. 1999). MTHFR is involved in the biotransformation
of folate and is highly polymorphic. Some mutations have been associated with
increased risks of malformations such as neural tube defects, cleft palate and
congenital heart disease that are often seen in relation to exposure to AEDs.
Bioactivation of AEDs to toxic reactive intermediate metabolites has been
another suggested mechanism for the teratogenic effects (Amore et al. 1997;
Bennett et al. 1996; Buehler et al. 1994; Finnell et al. 1995; Finnell and Dansky
1991; Lillibridge et al. 1996; Lindhout et al. 1984; Martz et al. 1977; Pantarotto
et al. 1982; Rane and Peng 1985; Roy and Snodgrass 1990; Strickler et al. 1985).
Reactive epoxides could be the result of CYP450 mediated oxidation of phenytoin,
carbamazepine or phenobarbital. Individual differences in rates of their formation
and in their elimination could contribute to the individual susceptibility to adverse
outcomes. This could be genetically determined as well as affected by interactions
between different AEDs. However, some of the most potent teratogenic AEDs such
as trimethadione lack the premises to form epoxides. Additionally, the CYP450
activity in the embryo during the sensitive periods is very low.
Another postulated bio-activating pathway is co-oxidation of AEDs to free
radical intermediates. These could release reactive oxygen species (ROS), which
may cause oxidative stress and thus teratogenicity. Deficiency of free radical
scavenging enzymes, responsible for eliminating ROS, has been associated with
malformations in the offspring of epileptic mothers exposed to AEDs (Parman et al.
1998; Wells et al. 1997; Wells and Winn 1996).
A more recent hypothesis suggests that many AEDs, such as phenytoin,
trimethadione, carbamazepine, phenobarbital, and possibly lamotrigine may exert
their teratogenic effects by inducing embryonic cardiac arrhythmia during specific
sensitive restricted periods (Danielsson et al. 2000). These effects on the embryonic
heart have been linked to the drugs’ ability to block the rapid component of the
delayed rectifying K ion current, Ikr (Azarbayjani and Danielsson 2002). It is
postulated that the embryonic arrhythmia will cause temporary hypoxia followed
by re-oxygenation and generation of ROS, which will cause tissue damage. Oro-
facial clefts, heart defects, distal digital defects and growth retardation could be
hypoxia related and thus explained by such mechanisms.
A different proposed mechanism postulates that the teratogenic effects of AEDs

may be explained by induction of neural apoptosis. Animal experiments have
demonstrated apoptotic neurodegeneration in the developing brain induced by
therapeutic concentrations of AEDs such as valproate, phenytoin, and phenobarbi-
tal (Bittigau et al. 2002; Kluger and Meador 2008).
It is clear that the mechanisms behind developmental toxicity of AEDs are
presently far from completely understood. They are likely to be multiple and differ
between individual AEDs and it is even conceivable that each individual AED can
exert its adverse effects through more than one mechanism.
9 Conclusions
It has been known for more than 40 years that children of mothers with epilepsy
have an increased risk of adverse pregnancy outcomes. Although multifactorial, the
greater risk is mainly due to teratogenic effects of the AEDs. However, due to the
significant maternal and foetal risks associated with uncontrolled epileptic seizures,
AED treatment is generally maintained during pregnancy in the majority of women
with active epilepsy.
Adverse pregnancy outcomes that have been associated with AED exposure
include foetal growth retardation, major congenital malformations and impaired
postnatal cognitive development. In earlier publications, the prevalence of major
malformations in children exposed to AEDs has been 2–4 times higher than in the
general population. More recent studies suggest a smaller increase in malformation
rates. This seemingly more favourable outcome may be relating new treatment
strategies with less polytherapy, lower AED dosages and different AED selection.
Recent data from large prospective pregnancy registries have revealed differences
between AEDs in their teratogenic potential. Malformation rates have consistently
been higher in association with exposure to valproate than with carbamazepine and
lamotrigine. Other, albeit more limited, prospective cohort studies also indicate
reduced cognitive outcome in children exposed to valproate compared to carba-
mazepine and possibly lamotrigine. Information on pregnancy outcomes with
newer generation AEDs other than lamotrigine are still insufficient.
References
Adab N, Jacoby A, Smith D et al (2001) Additional educational needs in children born to mothers
with epilepsy. J Neurol Neurosurg Psychiatry 70:15–21
Adab N, Kini U, Vinten J et al (2004a) The longer term outcome of children born to mothers with
epilepsy. J Neurol Neurosurg Psychiatry 75:1575–1583
Adab N, Tudur SC, Vinten J et al (2004b) Common antiepileptic drugs in pregnancy in women
with epilepsy (Cochrane Review) The Cochrane Library. Wiley, Chichester
Amore BM, Kalhorn TF, Skiles GL et al (1997) Characterization of carbamazepine metabolism in

a mouse model of carbamazepine teratogenicity. Drug Metab Dispos 25:953–962
Artama M, Auvinen A, Raudaskoski T et al (2005) Antiepileptic drug use of women with epilepsy
and congenital malformations in offspring. Neurology 64:1874–1878
Azarbayjani F, Danielsson BR (2002) Embryonic arrhythmia by inhibition of HERG channels: a
common hypoxia-related teratogenic mechanism for antiepileptic drugs? Epilepsia
43:457–468
Battino D, Tomson T (2007) Management of epilepsy during pregnancy. Drugs 67:2727–2746
Battino D, Granata T, Binelli S et al (1992) Intrauterine growth in the offspring of epileptic
mothers. Acta Neurol Scand 86:555–557
Battino D, Kaneko S, Andermann E et al (1999) Intrauterine growth in the offspring of epileptic
women: a prospective multicenter study. Epilepsy Res 36:53–60
Bennett GD, Amore BM, Finnell RH et al (1996) Teratogenicity of carbamazepine-10, 11-epoxide
and oxcarbazepine in the SWV mouse. J Pharmacol Exp Ther 279:1237–1242
Bittigau P, Sifringer M, Genz K et al (2002) Antiepileptic drugs and apoptotic neurodegeneration
in the developing brain. Proc Natl Acad Sci USA 99:15089–15094
Buehler BA, Delimont D, van Waes M et al (1990) Prenatal prediction of risk of the fetal
hydantoin syndrome. N Engl J Med 322:1567–1572
Buehler BA, Rao V, Finnell RH (1994) Biochemical and molecular teratology of fetal hydantoin
syndrome. Neurol Clin 12:741–748
Canger R, Battino D, Canevini MP et al (1999) Malformations in offspring of women with
epilepsy: a prospective study. Epilepsia 40:1231–1236
Choulika S, Harvey E, Holmes LB (1999) Effect of antiepileptic drugs (AED) on fetal growth:
assessment at birth. Teratology 59:388
Cunnington M, Ferber S, Quartey G (2007) Effect of dose on the frequency of major birth defects
following fetal exposure to lamotrigine monotherapy in an international observational study.
Epilepsia 48:1207–1210
Danielsson B, Skold AC, Azarbayjani F et al (2000) Pharmacokinetic data support pharmaco-
logically induced embryonic dysrhythmia as explanation to Fetal Hydantoin Syndrome in rats.
Toxicol Appl Pharmacol 163:164–175
Dansky LV, Andermann E, Rosenblatt D et al (1987) Anticonvulsants, folate levels, and preg-
nancy outcome: a prospective study. Ann Neurol 21:176–182
Dean JC, Moore SJ, Osborne A et al (1999) Fetal anticonvulsant syndrome and mutation in the
maternal MTHFR gene. Clin Genet 56:216–220
Dean JC, Hailey H, Moore SJ et al (2002) Long term health and neurodevelopment in children
exposed to antiepileptic drugs before birth. J Med Genet 39:251–259
Dessens AB, Cohen-Kettenis PT, Mellenbergh GJ et al (2001) Association of prenatal phenobar-
bital and phenytoin exposure with genital anomalies and menstrual disorders. Teratology
64:181–188
Dolk H, Jentink J, Loane M et al (2008) Does lamotrigine use in pregnancy increase orofacial cleft
risk relative to other malformations? Neurology 71:714–722
Eriksson K, Viinikainen K, Monkkonen A et al (2005) Children exposed to valproate in utero-
population based evaluation of risks and confounding factors for long-term neurocognitive
development. Epilepsy Res 65:189–200
Finnell RH (1991) Genetic differences in susceptibility to anticonvulsant drug-induced develop-
mental defects. Pharmacol Toxicol 69:223–227
Finnell RH, Dansky LV (1991) Parental epilepsy, anticonvulsant drugs, and reproductive out-
come: epidemiologic and experimental findings spanning three decades; 1: animal studies.
Reprod Toxicol 5:281–299
Finnell RH, Bennett GD, Slattery JT et al (1995) Effect of treatment with phenobarbital
and stiripentol on carbamazepine-induced teratogenicity and reactive metabolite formation.
Teratology 52:324–332
Fonager K, Larsen H, Pedersen L et al (2000) Birth outcomes in women exposed to anticonvulsant

drugs. Acta Neurol Scand 101:289–294
Fried S, Kozer E, Nulman I et al (2004) Malformation rates in children of women with untreated
epilepsy: a meta-analysis. Drug Saf 27:197–202
Gaily E (1991) Development and growth in children of epileptic mothers. A prospective controlled
study. Acta Obstet Gynecol Scand 70:631–632
Gaily E, Granstrom ML, Hiilesmaa V et al (1988) Minor anomalies in offspring of epileptic
mothers. J Pediatr 112:520–529
Gaily E, Kantola-Sorsa E, Granstrom ML (1990) Specific cognitive dysfunction in children with
epileptic mothers. Dev Med Child Neurol 32:403–414
Gaily E, Kantola-Sorsa E, Hiilesmaa V et al (2004) Normal intelligence in children with prenatal
exposure to carbamazepine. Neurology 62:28–32
German J, Ehlers KH, Kowal A et al (1970) Possible teratogenicity of trimethadione and
paramethadione. Lancet 2:261–262
Hanson JW, Myrianthopoulos NC, Harvey MA et al (1976) Risks to the offspring of women
treated with hydantoin anticonvulsants, with emphasis on the fetal hydantoin syndrome.
J Pediatr 89:662–668
Harden CL, Meador KJ, Pennell PB et al (2009) Management issues for women with epilepsy –
focus on pregnancy (an evidence-based review): II. Teratogenesis and perinatal outcomes:
report of the Quality Standards Subcommittee and Therapeutics and Technology Subcommit-
tee of the American Academy of Neurology and the American Epilepsy Society. Epilepsia
50:1237–1246
Hernandez-Diaz S, Smith CR, Wyszynski DF et al (2007) Risk of major malformations among
infants exposed to carbamazepine during pregnancy. Birth Def Res 79:357
Hiilesmaa VK, Teramo K, Granstrom ML et al (1981) Fetal head growth retardation associated
with maternal antiepileptic drugs. Lancet 2:165–167
Holmes LB, Rosenberger PB, Harvey EA et al (2000) Intelligence and physical features of
children of women with epilepsy. Teratology 61:196–202
Holmes LB, Harvey EA, Coull BA et al (2001) The teratogenicity of anticonvulsant drugs. N Engl
J Med 344:1132–1138
Holmes LB, Wyszynski DF, Lieberman E (2004) The AED (antiepileptic drug) pregnancy
registry: a 6-year experience. Arch Neurol 61:673–678
Holmes LB, Baldwin EJ, Smith CR et al (2008a) Increased frequency of isolated cleft palate in
infants exposed to lamotrigine during pregnancy. Neurology 70:2152–2158
Holmes LB, Smith CR, Herndandez-Diaz S (2008b) Pregnancy registries: larger sample sizes
essential. Birth Def Res A 82:307
Hunt S, Craig J, Russell A et al (2006) Levetiracetam in pregnancy: preliminary experience from
the UK Epilepsy and Pregnancy Register. Neurology 67:1876–1879
Hunt S, Russell A, Smithson WH et al (2008) Topiramate in pregnancy: preliminary experience
from the UK Epilepsy and Pregnancy Register. Neurology 71:272–276
Hvas CL, Henriksen TB, Ostergaard JR et al (2000) Epilepsy and pregnancy: effect of antiepileptic
drugs and lifestyle on birthweight. BJOG 107:896–902
Kaaja E, Kaaja R, Hiilesmaa V (2003) Major malformations in offspring of women with epilepsy.
Neurology 60:575–579
Kallen AJ (1994) Maternal carbamazepine and infant spina bifida. Reprod Toxicol 8:203–205
Kaneko S, Battino D, Andermann E et al (1999) Congenital malformations due to antiepileptic
drugs. Epilepsy Res 33:145–158
Kini U, Adab N, Vinten J et al (2006) Dysmorphic features: an important clue to the diagnosis and
severity of fetal anticonvulsant syndromes. Arch Dis Child Fetal Neonatal Ed 91:F90–F95
Kjaer D, Horvath-Puho E, Christensen J et al (2007) Use of phenytoin, phenobarbital, or diazepam
during pregnancy and risk of congenital abnormalities: a case-time-control study. Pharmacoe-
pidemiol Drug Saf 16:181–188
Kluger BM, Meador KJ (2008) Teratogenicity of antiepileptic medications. Semin Neurol

28:328–335
Kondo T, Kaneko S, Amano Y et al (1996) Preliminary report on teratogenic effects of zonisamide
in the offspring of treated women with epilepsy. Epilepsia 37:1242–1244
Lillibridge JH, Amore BM, Slattery JT et al (1996) Protein-reactive metabolites of carbamazepine
in mouse liver microsomes. Drug Metab Dispos 24:509–514
Lindhout D, Omtzigt JG (1992) Pregnancy and the risk of teratogenicity. Epilepsia 33:S41–S48
Lindhout D, Schmidt D (1986) In-utero exposure to valproate and neural tube defects. Lancet
1:1392–1393
Lindhout D, Hoppener RJ, Meinardi H (1984) Teratogenicity of antiepileptic drug combinations
with special emphasis on epoxidation (of carbamazepine). Epilepsia 25:77–83
Long L (2003) Levetiracetam monotherapy during pregnancy: a case series. Epilepsy Behav
4:447–448
Malm H, Kajantie E, Kivirikko S et al (2002) Valproate embryopathy in three sets of siblings:
further proof of hereditary susceptibility. Neurology 59:630–633
Martz F, Failinger C 3rd, Blake DA (1977) Phenytoin teratogenesis: correlation between
embryopathic effect and covalent binding of putative arene oxide metabolite in gestational
tissue. J Pharmacol Exp Ther 203:231–239
Meador K, Reynolds MW, Crean S et al (2008) Pregnancy outcomes in women with epilepsy: a
systematic review and meta-analysis of published pregnancy registries and cohorts. Epilepsy
Res 81:1–13
Meador KJ, Baker GA, Browning N et al (2009) Cognitive function at 3 years of age after fetal
exposure to antiepileptic drugs. N Engl J Med 360:1597–1605
Meadow SR (1968) Anticonvulsant drugs and congenital abnormalities. Lancet 2:1296
Meischenguiser R, D’Giano CH, Ferraro SM (2004) Oxcarbazepine in pregnancy: clinical experi-
ence in Argentina. Epilepsy Behav 5:163–167
Montouris G (2003) Gabapentin exposure in human pregnancy: results from the Gabapentin
Pregnancy Registry. Epilepsy Behav 4:310–317
Moore SJ, Turnpenny P, Quinn A et al (2000) A clinical study of 57 children with fetal anticon-
vulsant syndromes. J Med Genet 37:489–497
Morrow J, Russell A, Guthrie E et al (2006) Malformation risks of antiepileptic drugs in
pregnancy: a prospective study from the UK Epilepsy and Pregnancy Register. J Neurol
Neurosurg Psychiatry 77:193–198
Morrow JI, Hunt SJ, Russell AJ et al (2009) Folic acid use and major congenital malformations in
offspring of women with epilepsy: a prospective study from the UK Epilepsy and Pregnancy
Register. J Neurol Neurosurg Psychiatry 80:506–511
MRC Vitamin Study Research Group (1991) Prevention of neural tube defects: results of the
Medical Research Council Vitamin Study [see comments]. Lancet 338:131–137
Ogawa Y, Kaneko S, Otani K et al (1991) Serum folic acid levels in epileptic mothers and their
relationship to congenital malformations. Epilepsy Res 8:75–78
Ornoy A, Zvi N, Arnon J et al (2008) The outcome of pregnancy following topiramate treatment: a
study on 52 pregnancies. Reprod Toxicol 25:388–389
Pantarotto C, Arboix M, Sezzano P et al (1982) Studies on 5,5-diphenylhydantoin irreversible
binding to rat liver microsomal proteins. Biochem Pharmacol 31:1501–1507
Parman T, Chen G, Wells PG (1998) Free radical intermediates of phenytoin and related
teratogens. Prostaglandin H synthase-catalyzed bioactivation, electron paramagnetic reso-
nance spectrometry, and photochemical product analysis. J Biol Chem 273:25079–25088
Perucca E, Tomson T (2006) Prenatal exposure to antiepileptic drugs. Lancet 367:1467–1469
Puho EH, Szunyogh M, Metneki J et al (2007) Drug treatment during pregnancy and isolated
orofacial clefts in Hungary. Cleft Palate Craniofac J 44:194–202
Rane A, Peng D (1985) Phenytoin enhances epoxide metabolism in human fetal liver cultures.
Drug Metab Dispos 13:382–385
Rasalam AD, Hailey H, Williams JH et al (2005) Characteristics of fetal anticonvulsant syndrome

associated autistic disorder. Dev Med Child Neurol 47:551–555
Raymond GV, Buehler BA, Finnell RH et al (1995) Anticonvulsant teratogenesis: 3. Possible
metabolic basis. Teratology 51:55–56
Registry SMB http://www.janusinfo.org/. Accessed 2009
Rosa FW (1991) Spina bifida in infants of women treated with carbamazepine during pregnancy.
N Engl J Med 324:674–677
Roy D, Snodgrass WR (1990) Covalent binding of phenytoin to protein and modulation of
phenytoin metabolism by thiols in A/J mouse liver microsomes. J Pharmacol Exp Ther
252:895–900
Samrén EB, van Duijn CM, Koch S et al (1997) Maternal use of antiepileptic drugs and the risk of
major congenital malformations: a joint European prospective study of human teratogenesis
associated with maternal epilepsy. Epilepsia 38:981–990
Samrén EB, van Duijn CM, Christiaens GC et al (1999) Antiepileptic drug regimens and major
congenital abnormalities in the offspring. Ann Neurol 46:739–746
Scolnik D, Nulman I, Rovet J et al (1994) Neurodevelopment of children exposed in utero to
phenytoin and carbamazepine monotherapy. JAMA 271:767–770
Speidel BD, Meadow SR (1972) Maternal epilepsy and abnormalities of fetus and the newborn.
Lancet 2:839–843
Spina E, Perugi G (2004) Antiepileptic drugs: indications other than epilepsy. Epileptic Disord
6:57–75
Strickler SM, Dansky LV, Miller MA et al (1985) Genetic predisposition to phenytoin-induced
birth defects. Lancet 2:746–749
ten Berg K, Samrén EB, van Oppen AC et al (2005) Levetiracetam use and pregnancy outcome.
Reprod Toxicol 20:175–178
Thomas SV, Ajaykumar B, Sindhu K et al (2008) Motor and mental development of infants
exposed to antiepileptic drugs in utero. Epilepsy Behav 13:229–236
Tomson T, Battino D (2005) Teratogenicity of antiepileptic drugs: state of the art. Curr Opin
Neurol 18:135–140
Tomson T, Battino D (2009) The management of epilepsy in pregnancy. In: Shorvon S, Pedley TA
(eds) The epilepsies 3: blue books of neurology. Saunders Elsevier, Philadelphia, pp 241–264
Tomson T, Hiilesmaa V (2007) Epilepsy in pregnancy. BMJ 335:769–773
Tomson T, Beghi E, Sundqvist A et al (2004a) Medical risks in epilepsy: a review with focus on
physical injuries, mortality, traffic accidents and their prevention. Epilepsy Res 60:1–16
Tomson T, Perucca E, Battino D (2004b) Navigating toward fetal and maternal health: the
challenge of treating epilepsy in pregnancy. Epilepsia 45:1171–1175
Tomson T, Battino D, Craig J et al (2010) Pregnancy registries: differences, similarities, and
possible harmonization. Report of a working group of the Commission on Therapeutic
Strategies of the International League Against Epilepsy. Epilepsia 51:909–915
Vajda FJ, Hitchcock A, Graham J et al (2007) The Australian Register of Antiepileptic Drugs in
Pregnancy: the first 1002 pregnancies. Aust N Z J Obstet Gynaecol 47:468–474
Veiby G, Daltveit AK, Engelsen BA et al (2009) Pregnancy, delivery, and outcome for the child in
maternal epilepsy. Epilepsia 50:2130–2139
Viinikainen K, Heinonen S, Eriksson K et al (2006) Community-based, prospective, controlled
study of obstetric and neonatal outcome of 179 pregnancies in women with epilepsy. Epilepsia
47:186–192
Vinten J, Adab N, Kini U et al (2005) Neuropsychological effects of exposure to anticonvulsant
medication in utero. Neurology 64:949–954
Volcik KA, Shaw GM, Lammer EJ et al (2003) Evaluation of infant methylenetetrahydrofolate
reductase genotype, maternal vitamin use, and risk of high versus low level spina bifida
defects. Birth Defects Res A Clin Mol Teratol 67:154–157
Wells PG, Winn LM (1996) Biochemical toxicology of chemical teratogenesis. Crit Rev Biochem
Mol Biol 31:1–40
Wells PG, Kim PM, Laposa RR et al (1997) Oxidative damage in chemical teratogenesis. Mutat
Res 396:65–78
Wide K, Winbladh B, Tomson T et al (2000) Body dimensions of infants exposed to antiepileptic
drugs in utero: observations spanning 25 years. Epilepsia 41:854–861
Wide K, Henning E, Tomson T et al (2002) Psychomotor development in preschool children
exposed to antiepileptic drugs in utero. Acta Paediatr 91:409–414
Wide K, Winbladh B, Kallen B (2004) Major malformations in infants exposed to antiepileptic
drugs in utero, with emphasis on carbamazepine and valproic acid: a nation-wide, population-
based register study. Acta Paediatr 93:174–176
Wyszynski DF, Nambisan M, Surve T et al (2005) Increased rate of major malformations in
offspring exposed to valproate during pregnancy. Neurology 64:961–965
Zhu H, Kartiko S, Finnell RH (2009) Importance of gene-environment interactions in the etiology
of selected birth defects. Clin Genet 75:409–423
Preventive Medicines
Vaccination, Prophylaxis of Infectious Diseases,
Disinfectants
Ulrich Heininger
Contents
1 Vaccination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 318
1.1 Development of Vaccines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 320
1.2 Preclinical Vaccine Trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 321
1.3 Clinical Vaccine Trials . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 324
1.4 Specific Pediatric Aspects in Pre-licensure Vaccine Trials . . . . . . . . . . . . . . . . . . . . . . . . . 327
1.5 Licensure of Vaccines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
1.6 Vaccine Safety Assessment in Post-marketing Settings . . . . . . . . . . . . . . . . . . . . . . . . . . . . 328
2 Prophylaxis of Infectious Diseases . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 330
2.1 Avoidance of Exposure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
2.2 Pre- or Post-exposure Passive Immunization . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 331
3 Disinfectants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 333
3.1 Alcohol . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
3.2 Aldehydes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 334
3.3 Phenolics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
3.4 Quaternary Ammonium Compounds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
3.5 Oxidizing Agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
3.6 Iodine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 335
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 336
Abstract Immunizations belong to the most successful interventions in medicine.

Like other drugs, vaccines undergo long periods of pre-clinical development,
followed by careful clinical testing through study Phases I, II, and III before they
receive licensure. A successful candidate vaccine will move on to be an investiga-
tional vaccine to undergo three phases of pre-licensure clinical trials in a stepwise
fashion before it can be considered for approval, followed by an optional fourth
phase of post-marketing assessment. The overall risk–benefit assessment of a
U. Heininger (*)
Universit€ats-Kinderspital beider Basel (UKBB), Postfach, CH-4005 Basel, Switzerland
e-mail: Ulrich.Heininger@ukbb.ch

318 U. Heininger
candidate vaccine is very critical in making the licensure decision for regulatory
authorities, supported by their scientific committees. It includes analyses of immu-
nogenicity, efficacy, reactogenicity or tolerability, and safety of the vaccine. Public
trust in vaccines is a key to the success of immunization programs worldwide.
Maintaining this trust requires knowledge of the benefits and scientific understand-
ing of real or perceived risks of immunizations.
Under certain circumstances, pre- or post-exposure passive immunization can be
achieved by administration of immunoglobulines. In terms of prevention of infec-
tious diseases, disinfection can be applied to reduce the risk of transmission of
pathogens from patient to patient, health-care workers to patients, patients to
health-care workers, and objects or medical devices to patients.
Keywords Vaccination • Immunization • Vaccine efficacy • Vaccine safety •

Disinfection
1 Vaccination
Immunizations belong to the most successful interventions in medicine. During the

last few decades, impressive success has been achieved worldwide with population-
based immunization programs against several serious infectious diseases such as
tetanus, diphtheria, pertussis, poliomyelitis, measles, rubella embryopathy, and –
more recently – invasive bacterial infections caused by Haemophilus influenzae
type b, Neisseria meningitidis, Streptococcus pneumoniae, and Human Papilloma
Viruses (Gessner and Adegbola 2008; CDC 2008; De Wals et al. 2004). Table 1
presents a historical overview of major developments of vaccines for use in
humans.
Like other drugs, vaccines undergo long periods of pre-clinical development,
followed by careful clinical testing through study Phases I, II, and III before they
receive licensure for marketing. After a vaccine has been licensed by regulatory
authorities, national and international committees may formulate recommenda-
tions on their use in the broad population. Frequently, reimbursement by health
insurances accompanies these recommendations and thereby supports successful
implementation. An integral part of implemented vaccines is continuous surveil-
lance of their effectiveness (mainly by means of epidemiological studies) and safety
(mainly by mandatory reporting of serious “Adverse Events Following Immuniza-
tion”, AEFI). While in the safety assessment of drugs other than vaccines the term
“Adverse Drug Reaction” is commonly used, the term “Adverse Events Following
Immunization” is internationally preferred in the context of vaccines and will
therefore be used here.
Unfortunately, success of immunizations is continuously being threatened today
by a phenomenon coined as “vaccines shovelling their own grave” (Heininger
2004). This means, as the incidence of previously frequent, potentially devastating
diseases will decrease due to successful immunization programs, public focus may
Preventive Medicines 319
Table 1 Milestones in the development of vaccines for use in humans

Yeara Live-attenuated Inactivated Component vaccines Gene technology
vaccines whole organism (inactivated)
vaccines
1885 Rabies
1896 Typhoid fever
1896 Cholera
1897 Plague
1923 Diphtheria toxoid
1926 Pertussis
1927 Tuberculosis Tetanus toxoid
1935 Yellow fever
1936 Influenza
1955 Poliomyelitis
1960 Poliomyelitis
1967 Mumps
1968 Measles
1969 Rubella
1971 Influenza (reassortant)
1971 FSME
1974 Varicella
1975 Typhoid
1977 Pneumococcal
polysaccharides
(14-valent)
1980 Tick-borne encephalitis
1981 Hepatitis B surface
antigen (plasma
derived)
1981 Pertussis (acellular)
1982 Meningococcal
polysaccharides
(tetravalent)
1984 Pneumococcal
polysaccharides
(23-valent)
1985 Hib (polysaccharide)
1986 Hepatitis B surface Yeast derived
antigen
1987 Hib (protein conjugated)
1992 Hepatitis A
1998 Rotavirus Rhesus assortant
1999 Meningococcal group C
(protein conjugated)
2000 Pneumococcal (protein
conjugated, 7-valent)
2003 Influenza Cold adapted,
intranasal
(trivalent)
2005 MMR-V combination
vaccine
2005 Rotavirus Bovine, assortant
(pentavalent)
Humane, assortant
(monovalent)
(continued)
320 U. Heininger
Table 1 (continued)
Yeara Live-attenuated Inactivated Component vaccines Gene technology
vaccines whole organism (inactivated)
vaccines
2006 Meningococcal groups A,
C,W135,Y (protein
conjugated)
2006/2007 Human HPV-6, -11, -16, -18
papilloma (quadrivalent),
virus (HPV) HPV-16, -18
(bivalent)
2007 Herpes zoster
2009 Pneumococcal (protein
conjugated, 10-valent
and 13-valent)
a
First used routinely in humans
shift towards true and alleged “side effects” of vaccines. This can lead to the
dilemma of waning public confidence in the necessity, tolerability, and safety of
vaccinations (Guillaume and Bath 2008). It is therefore important to continuously
evaluate risks and benefits of vaccines and results of these evaluations need to be
openly communicated to health professionals and the public in order to strengthen
the confidence in existing and new immunization programs.
1.1 Development of Vaccines
There are several prerequisites for successful and meaningful vaccine development
which include the following:
• The microorganism (or its specific mediators of disease, such as toxins and other
major virulence factors) that causes an infectious disease needs to be identified
• Characteristics of the causative agent that leads to disease in the human host
should be explored in order to determine the optimal composition of the vaccine
to be designed against it
• Protective immune responses against the targeted microorganism in the human
host need to be explored in order to identify the optimal route of delivery
(mucosal, systemic) of the vaccine antigen(s)
• The disease is severe enough, i.e. life threatening or even potentially fatal,
leading to significant complications and/or the disease is frequent enough to
cause a significant health or economic burden in the population. This requires
precise description of the overall (or regional) distribution and frequency of the
disease by age groups and characterization of complications caused by the
targeted disease. Frequently this is required on a national basis, if possible, as
immunization recommendations will usually also be formulated nationally
• Lack of successful and rational alternatives to prevent and/or treat the targeted
disease
• Incentives for investment in the development of a new vaccine by research
groups and/or manufacturers should be secured
• Public perception of the infectious disease against which a vaccine is to be

developed should be such that prevention by immunization is warranted
The microorganism against which a vaccine is to be developed has to be
characterized in great detail and needs to be multiplied, harvested, and worked up
under “Good Laboratory Practice” principles to fulfill the requirements of the final
product. This includes strict safety and quality control measurements.
In the case of live-attenuated vaccines, safety of the attenuated live organisms
has to be guaranteed and proven. In the case of inactivated vaccines, a decision has
to be made whether the whole organism should serve as the immunological target
(e.g. hepatitis A) or one (e.g. tetanus toxin) or more specific virulence factors (e.g.
pertussis toxin, filamentous haemagglutinin, and pertactin in the case of acellular
pertussis vaccines) will serve this purpose. The decision on this depends mainly on
basic scientific work on the pathogenesis of the microorganism and the mechanisms
of the human host’s immune response.
This work may require years, sometimes decades, of continuous basic research
which is frequently initiated in academic or private research laboratories before the
pharmaceutical industry takes over the task of developing a vaccine. This requires
significant investment and carries the risk of failure at any step of the vaccine’s
development.
1.2 Preclinical Vaccine Trials
Preclinical vaccine trials are being performed under the principles of “Good
Manufacturing Practices”, as established by major regulatory and scientific
authorities such as the US Food and Drug Administration (FDA) and the European
Medicines Agency (EMA, formerly called EMEA). Specifically, EMA has devel-
oped guidelines for the development of medicines for paediatric use, including
vaccines (http://www.ema.europa.eu/pdfs/human/qwp/13893108en.pdf) which
specify the particular needs for such products in infants and children, including
pre-term infants.
For preclinical testing of a candidate vaccine, adequate preparations are first
tested in cell culture or tissue culture systems. If results are promising, the candidate
will then enter the phase of testing in animals such as mice, rats, guinea pigs or
sometimes even primates (usually monkeys). More recently, three-dimensional
visualization of vaccine compounds by use of sophisticated computer technology
has entered preclinical testing. This technology can assist researchers to predict
how a candidate vaccine will interact with the host’s immune system.
Further, preclinical tests comprise
• Proof of non-toxicity:
Local and systemic toxicity is first assessed in appropriate animal models and
in vitro settings before clinical testing in humans can be initiated. Further,
mutagenicity needs to be assessed as some chemical compounds included in
322 U. Heininger
vaccines may potentially act as base analogs and get inserted into the DNA strand
during replication instead of the natural substrates. Other compounds may react
with DNA and cause structural changes that can lead to miscopying of the
template strand when the DNA is replicated. Similarly, carcinogenicity of vac-
cine compounds may be of concern, especially when the microorganism against
which the vaccine is directed can lead to cancer, for example, human papilloma
virus. Carcinogens alter the cellular metabolism or directly damage DNA in cells
by inducing uncontrolled cell division, inhibiting the programmed cell death,
leading to malignant cell expansion and finally the development of tumours.
• Pharmacodynamic and pharmacokinetic vaccine trials:
The main purpose of these early steps in preclinical testing in animal models is to
estimate the appropriate content of vaccine antigens (dose) and schedule of
administration (number of doses, intervals). This is followed by secondary
vaccine trials on the dose effect, tolerability, and distribution of vaccine antigens
in different organs of the immunized host (¼primary safety assessment).
• Product characteristics:
After a candidate vaccine has successfully passed non-toxicity and pharmaco-
dynamic and pharmacokinetic vaccine trials, the next step before entering
clinical vaccine trials is demonstration of a reliable production process. This
requires demonstration of genetic stability of the seed microorganism (which is
repeatedly used to produce consecutive batches of vaccine), stability and purity
(i.e., absence of substances introduced during the manufacturing process which
are neither needed nor accepted to be present in the final product) of the vaccine
formulation, and characterization of its shelf life under defined storing
conditions (e.g. cold temperature, room temperature conditions etc.).
If the vaccine candidate performs to the researchers’ satisfaction during these
preclinical evaluations, it will be called “investigational vaccine” and can finally be
used in human volunteers in Clinical Vaccine Trials.
Traditionally, most inactivated vaccines have been supplemented by chemicals
called adjuvants which support the host’s immune response to vaccine antigens.
This is frequently necessary to allow a sufficient immune response without increas-
ing the antigen content to a magnitude which would cause significant intolerability
due to side effects (e.g. large local injection site swelling or febrile reactions). In the
past, most adjuvants have been chemical formulations based on aluminium, mainly
in the form of aluminium hydroxide (AlOH) and phosphate (AlPO4). More
recently, new (modern) adjuvants have entered clinical testing and proven success-
ful by means of better immunogenicity and similar tolerability in terms of local and
systemic reactions in the immunized human host including young children, immu-
nocompromised individuals, and elderly people (Pichichero 2008).
An overview of selected promising or proven to be successful new adjuvants is
shown in Table 2.
• The adjuvant system 02 (AS02) is included in the currently most advanced anti-
malaria vaccine, undergoing clinical testing in Phase III vaccine trials in children
and adults in several African countries (Sacarlal et al. 2009; Abdulla et al 2008).
Table 2 New adjuvants in vaccines for use in humans
Preventive Medicines
Adjuvant Characteristics Vaccine (manufacturer) Stage of clinical References

testing
AS02 Oil-in water emulsion: monophosphoryl P. falciparum, malaria Phase II/III (Africa) Cooper et al. (2004) and De Wals et al.
lipid (MPL A) and saponin-type (GlaxoSmithKline) (2004)
detergent (QS21)
AS04 Oil-in water emulsion: monophosphoryl Hepatitis B; Human papilloma Licensed De Stefano et al. (2004), Dettenkofer and
lipid (MPL A) and aluminium virus, cervical and other Daschner (1997) and Didierlaurent
hydroxide cancers (GlaxoSmithKline) et al. (2009)
CpG 7907 24-mer B-Class CpG Hepatitis B; P. falciparum, Phase I/II Ellebedy and Webby (2009) and Gessner
Oligodeoxynucleotide malaria (GlaxoSmithKline) and Adegbola (2008)
AS03 Oil-in water emulsion: Squalen, Influenza, novel H1N1 vaccine Licensed Giannini et al. (2006)
Tocopherol (Vitamine E) and (GlaxoSmithKline)
Polysorbat 80 in a phosphate buffer
MF59 Oil-in water emulsion: Squalen, polysorbat Influenza, including novel H1N1 Licensed Gr€
uber et al. (2003), Guillaume and Bath
(Tween 80), and Sorbitantrioleat (Span vaccine (Novartis) (2008) and Heininger (2003)
85)
323
324 U. Heininger
It induces strong immune-specific responses and the vaccine has proven suc-
cessful in Phase II vaccine trials.
• The adjuvant system 04 (AS04) combines the TLR4 agonist MPL (3-O-desacyl-
40 -monophosphoryl lipid A) and aluminium salt. It has first been used in hepatitis
B conventional vaccine non-responders and immunocompromised hosts (Boland
et al. 2004). Its further inclusion in novel anti-human papilloma virus vaccines,
aimed at precancerous lesions and cancer primarily in the female genital
tract (cervical cancer and others), has led to the development of successful and
licensed vaccines for women 9–26 years of age (Giannini et al. 2006;
Didierlaurent et al 2009).
• CpG 7907 is an adjuvant that directly activates B-lymphocytes and
plasmacytoid dendritic cells and indirectly activates macrophages and other
monocytes by inducing the secretion of Th1-like cytokines and chemokines. It
also facilitates a Th1-type immune response via cytotoxic T-lymphocytes and
has been successfully tested in hepatitis B vaccines and malaria caused by
Plasmodium falciparum (Cooper et al. 2004, Sagara et al 2009) in Phase II
and III trials.
• Finally, oil-in-water adjuvants such as MF59 and adjuvant system 03 (AS03)
have recently been used to develop antigen sparing influenza vaccines against
the novel H1N1 subtype, also called “swine-flu” (www.emea.europa.eu/
humandocs/PDFs/. . ./pandemrix/H-832-de1.pdf; Ellebedy and Webby 2009;
Keitel et al. 2010). With the help of these adjuvants, vaccine antigen content
could be reduced by as much as sixfold compared to conventional, non-
adjuvanted influenza vaccines. Further, these adjuvanted vaccines induced
very potent immune responses after even a single dose administration. They
have been licensed and used worldwide during the winter in 2009/2010. More-
over, an MF59 adjuvanted seasonal influenza vaccine has been licensed and
made available for use in elderly individuals in Europe for several years and was
recently also shown to be of use in children (Vesikari et al 2009).
1.3 Clinical Vaccine Trials
Like any other drug, a successful candidate vaccine will move on to be an

investigational vaccine to undergo three phases of pre-licensure clinical trials in a
stepwise fashion before it can be considered for approval, followed by an optional
fourth phase of post-marketing assessment (Table 3).
Pre-licensure vaccine trials rely upon
• Dedicated basic and clinical research teams (usually in collaboration between
the manufacturer and one or more principal investigators from academic
research centers or other clinical trial units);
• Motivated and engaged local field investigators (frequently in multi-centre study
design, including hospital based and/or physicians in private practices);
Table 3 Phases of clinical testing of vaccines for use in humans

Phase I Assessment of tolerability and immunogenicity in a limited study population
(<100 healthy adult volunteers)
Phase II Testing of lot consistency; confirmation of acceptable tolerability; potentially
assessment of efficacy and reactogenicity and safety profile in extended study
populations (target age group or groups and/or targeted patient population;
>1,000 to >10,000 study subjects)
Phase III Confirmation of efficacy and/or safety (target age group or groups and/or targeted
patient population; >10,000 study subjects)
Phase IV Post-licensure assessment of safety and/or effectiveness (whole population or
representative sample of the population)
• The participation of hundreds to ten thousands of volunteers to be immunized

under study conditions;
• And professional clinical study organizations acquainted with the multiple legal
and logistic requirements in performing and monitoring such vaccine trials.
Post-marketing assessment of vaccines relies upon immunizing physicians and a
motivated study population (vaccinees), willing to assess a licensed vaccine under
further study conditions.
Further, continuous effectiveness and safety assessment of a given vaccine should
be undertaken after licensure, unlimited in time. This requires functional national and
international pharmacovigilance systems, implementation of epidemiological sur-
veillance systems, and ideally a mandatory reporting system for adverse events
following immunization (safety) but also for vaccination failures (effectiveness).
Clinical vaccine trials nowadays have to be registered in international databases
(e.g. www.clinicaltrials.gov). A typical volunteer in a vaccine study (called “vacci-
nee”) formally agrees to be vaccinated, to make frequent visits to a clinic or study
centre for evaluation, to participate in medical testing, and to provide blood or tissue
samples that are used to assess the vaccine’s performance in terms of tolerability,
immune response in the host (immunogenicity), safety, and efficacy. Research staff
counsel volunteers about the study, and volunteers must sign an informed consent
document, indicating their understanding of the study and their willingness to
participate.
Close collaboration of vaccine manufacturers, research teams, clinicians, regu-
latory authorities and study subjects or the broad population is needed for success-
ful performance of clinical vaccine trials throughout Phases I–IV.
The 3 phases of pre-licensure clinical vaccine trials fulfill the following purposes:
• Phase I
Dose finding (antigen content or amount of attenuated vaccine microorganisms)
and dose schedule (numbers of doses required and optimal intervals from dose to
dose); determination of acceptable local and systemic tolerability of the candi-
date vaccine and absence of toxicity in the human host.
• Phase II
326 U. Heininger
Lot consistency testing; confirmation of Phase I findings in terms of local and

systemic tolerability and absence of toxicity; preliminary determination of
efficacy and confirmation of Phase I immunogenicity results. Importantly,
study subjects will be recruited from the future target population for the vaccine
(age group or groups, possibly patients with specific conditions).
• Phase III
Critical (“pivotal”) phase with sufficient numbers of study subjects to confirm
Phase II findings and to proof efficacy or immunogenicity and safety of the
candidate vaccine in the target population.
Planning and conduction of Phase III vaccine trials is challenging. Depending on
the specific vaccine and clinical as well as epidemiological characteristics of its
targeted disease, different endpoints for proof of efficacy are required:
• If a serological (i.e., serum antibody level) correlate of immunity or protection
is known for a disease, proof of immunogenicity by demonstration that a
predetermined percentage of trial subjects (e.g. 99%) do reach the minimal
antibody level after immunization will be sufficient. Vaccine efficacy will then
be inferred from its immunogenicity. In this case, the number of trial participants
can be comparatively small (e.g. 100–200 per targeted age group). Examples for
vaccine preventable diseases with known serological correlates of protection are
hepatitis B, diphtheria, and tetanus.
• If there is no known correlate of immunity, clinical endpoints need to be defined
to assess a vaccine’s efficacy. If ethical circumstances allow, double-blind and
controlled prospective trials are the ideal design for calculation of vaccine
efficacy by comparing the incidence of disease (¼the clinical endpoint) in
the control group with that of the vaccine group. The percent reduction of
disease incidence in the vaccinated cohort will then define the vaccine’s efficacy.
If the clinical endpoint is a comparatively frequent disease (e.g. acute otitis
media), statistical power calculation will reveal a comparatively low number of
trial participants and/or short duration of the trial. If, however, the disease is rare
(e.g. meningitis), the number of trial participants has to be high and/or the
duration of the trial has to be sufficiently long to reach the number of cases in
the control group that will be needed for demonstration of vaccine efficacy.
• If there is no known correlate of immunity and the clinical endpoint is difficult to
assess, another level of complexity is added. This was the case with acellular
pertussis vaccine efficacy trials in the 1990s, where various endpoints for
“pertussis” depending on duration of cough illness and microbiological proof
of Bordetella pertussis infection were assessed in various trials (Stehr et al
1998). Similarly, if a vaccine protects from different disease manifestations as
clinical endpoints, different estimates of vaccines efficacy will result as is the
case with pneumococcal conjugate vaccines. Their efficacy against invasive
disease (meningitis, sepsis) is significantly higher than efficacy against pneumo-
nia or acute otitis media (Heininger 2003).
• If long-term efficacy and/or the need for booster doses of a specific vaccine have
to be determined, prolonged follow up of trial cohorts or sub-cohorts is
necessary in order to monitor persistence of immunity. Again, this will be done

by use of clinical endpoints and/or longitudinal testing of serum antibody values.
After completion of the clinical tests in pre-licensure vaccine trials, the candi-
date vaccine may be submitted to regulatory authorities for licensure.
Later on, Phase IV vaccine trials after licensure of the vaccine are designed to
investigate vaccine-specific issues that may have become apparent during pre-
licensure testing and which need specific attention in a large enough number of
vaccines. Some Phase IV vaccine trials will become necessary as specific issues
related to efficacy, safety, or tolerability of the vaccine only arise when the product
has already been used for a while in the population.
For these reasons, after licensure, further continuous assessment of the vaccine
may be requested by regulatory authorities. Justifications for performing such Phase
IV vaccine trials include determination of effectiveness (i.e., preventing the
targeted disease or some of its manifestations under field conditions rather than
under stringent study conditions) and further proof of safety beyond the limited
experience obtained during pre-licensure vaccine trials. This has become increas-
ingly important over the last several years as also very rare side effects (<1 per
10’000 doses) have been become of interest among the public and health
professionals recently. Especially when signals of potential safety problems were
detected in pre-licensure vaccine trials, the manufacturers are forced to perform
Phase IV vaccine trials to elucidate the issues which arose.
For example, an oral rotavirus vaccine (Rotashield®) was licensed in the US in
1998. During pre-licensure vaccine trials more cases of intussusception (defined as
the invagination of a proximal segment of intestine into a distal segment of
intestine, usually ileo-colic) occurred in rotavirus vaccine recipients compared to
controls (Kombo et al. 2001). Although the difference was not statistically signifi-
cant, for obvious reasons more data were required to draw firm conclusions. This
was an important issue, because intussusception results in obstruction of bowel
passage, constriction of the mesentery, and obstruction of the venous blood flow
which is characterized by sudden onset of colicky abdominal pain and can poten-
tially lead to death. After more than 1.5 million doses of vaccine had been used
within less than a year in the USA, an approximately threefold risk for intussuscep-
tion was discovered after vaccine doses 1 and 2 compared to unvaccinated, age-
matched control infants and the vaccine had to be taken off the market. This
example demonstrates both the necessity as well as the functionality of post-
marketing vaccine safety assessment today.
1.4 Specific Pediatric Aspects in Pre-licensure Vaccine Trials
Specific pediatric needs and requirements in the context of clinical vaccine trials on
drugs, including vaccines, have received special attention recently (http://www.
ema.europa.eu/htms/human/paediatrics/pips_procedural.htm).
328 U. Heininger
A new pediatric regulation (“The EU Paediatric Regulation”) became law in the

European Union (EU) on 26 January 2007. It was accompanied by a number of
specific regulations which not only provide precise guidelines for researchers and
manufacturers throughout the process of clinical testing but also protect the rights
of children as active study subjects. This is of special relevance in the context of
pre-licensure trials with vaccines as many of those are performed exclusively in
children, who are the only target population for a number of specific vaccines such
as combination vaccines which include Haemophilus influenzae type B polysac-
charide conjugate and/or high antigen content of diphtheria toxoid. The develop-
ment of vaccines in children has to follow a pediatric investigation plan (PIP) by the
manufacturers seeking licensure. Of note, all clinical vaccine trials performed with
children as participants must be registered in a database called EudraCT if the trial
is part of a PIP. This database is publicly accessible (https://eudract.emea.europa.
eu/index.html).
If ethical considerations suggest that testing of a specific vaccine in children
would pose them at unjustified risks (or if there is no intended application for a
specific vaccine in children), the regulation allows a limited “deferral” or even a full
exception (“waiver”).
1.5 Licensure of Vaccines
The overall risk–benefit assessment of a candidate vaccine is very critical in making

the licensure decision for regulatory authorities, supported by their scientific
committees. It includes analyses of immunogenicity, efficacy, reactogenicity or
tolerability, and safety of the vaccine.
Licensure or authorization of a vaccine can be requested by a manufacturer via
the “human unit” of EMA (“central approval”).
In addition to general authorization of a vaccine, each lot of a vaccine needs to
be tested and released. For this purpose, “Official Medicine Control Laboratories,
OMCL” have been assigned by the “European Directorate for the Quality of
Medicines, EDQM” in Strasbourg, France (http://www.edqm.eu).
1.6 Vaccine Safety Assessment in Post-marketing Settings
Public trust in vaccines is a key to the success of immunization programs world-

wide. Maintaining this trust requires knowledge of the benefits and scientific
understanding of real or perceived risks of immunizations.
The risk–benefit assessment, which vaccine recipients and providers need to
make continuously, should be based on evidence of best achievable quality.
In terms of reactogenicity, information on a specific vaccine can be found in the
“Summary of product characteristics”. By convention, side effects (i.e., events with
proven causal relationship to the vaccine) and adverse events following
immunization, AEFI (i.e., events which occur in temporal but not necessarily causal
relationship after immunization) are categorized by frequency of occurrence fol-
lowing the terminology as proposed by WHO (http://www.who.int/vaccines-
documents/DocsPDF05/815.pdf):
Causality assessment is also an integral part of vaccine safety evaluation. Assess-
ment of local reactions after injected vaccines (e.g. swelling, induration, injection site
pain) is straight forward: the time interval between immunization and occurrence of
the reaction is usually short (several hours to few days) and a causal association with
immunization therefore is obvious. Systemic reactions, however, such as fever or
malaise may or may not be causally related to previous immunization. Here, the kind
of vaccine (inactivated versus live-attenuated) determines the temporal relationship
between vaccination and occurrence of causally related side effects. The attributable
risk of a systemic event after vaccination has to be determined by comparing the
observed rate after vaccination with the background rate to see if and by which
magnitude it is increased. Again, this is straightforward in controlled vaccine trials.
For example, in a clinical study with an oral rotavirus vaccine, fever, and irritability
occurred in more than 50% of study subjects and loss of appetite, diarrhea, vomiting,
and cough in 20–60% (Ruiz-Palacios et al. 2007), irrespective of administration of
placebo or the vaccine. This example illustrates the difficulty to attribute systemic
adverse events after immunization to the vaccine in an individual. Of note, side
effects after vaccination are therefore a diagnosis of exclusion.
Admittedly, there are many examples of real side effects after vaccination. For
example, a nasal influenza vaccine that was available in Switzerland for a short
period of time clearly was temporally associated with an increased risk for periph-
eral facial palsy. The initial hypothesis of a causal relation was based on several
reports of facial palsy to the Swiss regulatory authority which had occurred shortly
after nasal influenza vaccine administration. In a well-organized post-marketing
surveillance system, these observations prompted a prospective controlled study
which finally proved that the relation to immunization was causal and not only
temporal (Mutsch et al. 2004).
Potential uncertainty about the safety of vaccines – particularly in countries
where some vaccine preventable diseases have disappeared from the public aware-
ness due to efficacious vaccines and high immunization rates in well structured
immunization programs – is currently aggravated by a large volume of unstructured
information of varying quality available to health care professionals and parents,
frequently via the worldwide web and other mass media. However, in the obvious
absence of perfectly safe health interventions, patients have the right to be objec-
tively advised about benefits and possible risks.
As mentioned, providing evidence of the safety of a given vaccine is of para-
mount importance. From a health professional’s perspective, this can be achieved
by individual search of the literature (which is time-consuming and can be cumber-
some especially when personal resources are limited) or reliance on informa-
tion provided by experts specialized in pharmacovigilance, public health, and
vaccinology. For these specialists, published information on characteristics of a
vaccine and study results is usually more easily accessible. However, scrutinizing
and evaluating the information again is cumbersome.
330 U. Heininger
In the past, a major obstacle to compare results of vaccine tolerability and safety
as published in scientific journals, has been the lack of standardized case definitions
for AEFI (Ioannidis and Lau 2001; Bonhoeffer et al. 2002). In the meantime, a
considerable number of standardized adverse event case definitions and guidelines
on how to use them has been developed by “The Brighton Collaboration” (http://
brightoncollaboration.org), an independent international organization, dedicated to
standardizing vaccine safety assessment (Kohl et al. 2007).These case definitions
have undergone (Tapiainen et al 2006) or are currently undergoing validation and
are increasingly recommended by national and international authorities including
WHO, EMA, FDA, and the US Centers for Disease Control (CDC).
The availability and use of standardized case definitions for certain AEFI will
improve vaccine safety assessment in the future for the following reasons:
• Clinical vaccine trials can be designed in a way that allows obtaining relevant
clinical information depending on the requirements of a given case definition.
• Metaanalyses of vaccine safety issues can be performed over different clinical
trials if the same standardized case definitions have been used in the individual
trials.
• Also clinical reports of AEFI in surveillance settings (post-marketing) can be
verified by use of standardized case definitions.
• Frequencies and incidences of AEFI as obtained from different surveillance
systems can be compared in a meaningful way if standardized case definitions
have been used.
The importance of alleged vaccine side effects, because of their influence on the
public perception of vaccine safety, needs to be stressed, too. After many carefully
conducted vaccine trials and plausibility assessments, the great majority of
suspected, mostly serious suspected “side effects” of specific vaccinations receiv-
ing public attention in the recent past have turned out to be coincidental
observations. These events include diabetes mellitus in young children after
Haemophilus influenzae type b vaccination (Black et al. 2002), autism and inflam-
matory bowel disease after measles–mumps–rubella (MMR) vaccine (De Stefano
et al. 2004), demyelinating diseases in adolescents after hepatitis B immunization
(Hocine et al. 2007), asthma after various childhood immunizations (Gr€uber et al.
2003), and sudden infant death syndrome (SIDS) after pertussis component
containing combination vaccines for infants (Stratton et al. 1994).
Differentiation between coincidence and causality therefore is of high impor-
tance to maintain public trust in immunization programs.
2 Prophylaxis of Infectious Diseases
In addition to active immunization, prophylaxis of infectious diseases can be

achieved by
• Avoidance of exposure
• Pre- or post-exposure passive immunization

• Pre- or post-exposure administration of antivirals or antibiotic administration
2.1 Avoidance of Exposure
Avoidance of exposure is difficult in daily practice, especially as many infections

are contagious before manifestation of disease, e.g. as in the case of measles and
varicella where contagiousness starts 2 days before the typical rash. Therefore,
avoidance of exposure is unrealistic most of the time, especially in close contact
persons. An exception is the situation of an outbreak, where transmission may be
ongoing for a prolonged period of time and contact isolation may be warranted
depending on individual circumstances.
2.2 Pre- or Post-exposure Passive Immunization
Pre- or post-exposure passive immunization can be achieved by administration of

immunoglobulines. Immunoglobulines, or antibodies, are proteins in blood and
other body fluids produced by specialized B-lymphocytes (plasma cells) which do
recognize bacteria, viruses, and other microorganisms invading the human host.
They are made of two large heavy chains and two small light chains. There are
different types of heavy chains which allow grouping of antibodies into different
isotypes. The different human antibody isotypes are called IgA, IgD, IgE, IgG, and
IgM. For prophylactic or therapeutic use, mainly IgG preparations and rarely IgM
preparations are being used. Human (“homologous”) immunoglobulin preparations
are obtained by Cohn fractionation (or ethanol fractionation) from the pooled
plasma of large numbers of healthy donors.
The Cohn fractionation primarily aims at extracting and recovering albumin
from the donor’s blood plasma. This process is based on the differential solubility
of albumin and other major plasma proteins depending on pH value, ethanol
concentration, temperature, ionic strength, and protein concentration in the solu-
tion. Here, albumin has the highest solubility and lowest isoelectric point of all
major human plasma proteins. Importantly, during Cohn’s fractionation, human
proteins such as the immunoglobulins will retain their biological activity. Further,
elimination of potential pathogenic microorganisms has to be assured by various
methodologies including filtration processes and radiation.
Immunoglobulin donors are selected by manufacturers based on particularly
high specific antibody values in their serum against a particular pathogen or its
known virulence factors, e.g. toxins, allowing production of a specific immuno-
globulin, formerly called hyper-immunoglobulin. Indications for the administration
of specific immunoglobulins are:
332 U. Heininger
Table 4 Immunoglobulinsa for passive immunization

Disease Producta Indication and dose Application
Hepatitis A Beriglobin Pre- and post-exposure: 0.02 ml/kg body i.m. or s.c.
weight (bw)
Hepatitis B Hepatitis-B- Post-exposure: 0.06 ml/kg bw (newborns: i.m.
immunglobulinb 1 ml total dose)
Hepatect CPb Post-exposure: 0.16–0.2 ml/kg bw i.v.
(newborns: 0.4 ml/kg bw)
Tetanus Tetagam Pboder Post-exposure: 1 (2) ml (independent of i.m.
Tetanobulin S/Db age). Therapeutic dose: 12–24 ml
Rabies Berirabb or Post-exposure: 0.14 ml/kg bw i.m.
Tollwutglobulin
Mérieux® Pb
Varicella Varitect CP Post-exposure: 1 (2) ml/kg bw i.v.
Cytomegaly Cytotect CP Pre-exposure: 1 ml/kg bw (at least 6 every i.v.
2–3 weeks)
a
Available in Germany
b
Simultaneously with active immunization
• Pre-or post-exposure prophylaxis of certain infectious diseases in susceptible

individuals for whom the respective disease would pose specific risks
• Pre-or post-exposure prophylaxis in rare but dangerous infectious diseases if it is
too late for active immunization (e.g. rabies prophylaxis after animal bites)
• Early treatment to neutralize toxin effects (such as those caused by diphtheria or
tetanus)
Typical indications, available products (in Germany), dosage and route of
administration are shown in Table 4.
Besides specific immunoglobulins, so-called homologous standard immuno-
globulins are available which reflect the whole repertoire of specific IgG antibodies
of the respective human donors. They find their applications
• For pre- or post-exposure prophylaxis of certain infectious diseases in suscepti-
ble individuals for whom the respective disease would pose a specific health risk
(e.g. measles, rubella, varicella)
• As a substitution in primary or secondary immunoglobulin deficiency states
• For the treatment of autoimmune diseases (e.g. idiopathic thrombocytopenia,
Rhesus factor incompatibility in the newborn, and Kawasaki syndrome)
In contrast to homologous immunoglobulins, heterologous immunoglobulins
against specific toxins are obtained from animals (e.g. horses immunized with the
respective toxin) by blood sampling. Since heterologous immunoglobulins can
induce severe allergic reactions including anaphylaxis, they are only used for
infections or intoxications for which no sufficient amounts of immunoglobulin
from homologous donors are available. These indications include protection from
or treatment against
• Corynebacterium diphtheriae (diphtheria)
• Clostridium botulinum (botulism)
• Clostridium perfringens (gas gangrene)

Futher, various preparations against snake and scorpion toxins are available.
They are rarely used in clinical practice. Unfortunately, immunoglobulins against
diphtheria toxin are no longer available in most parts of the world.
Before each administration of heterologous immunoglobulins, a pre-existing
allergy has to be ruled out in the individual patient. This is usually done by
preparing a 1:100 dilution of the immunoglobulin (0.1 ml in 10 ml 0.9% NaCl
solution) and one drop is applied on the volar forearm. Then the skin is punctured
though the drop with a small needle or lancet. As a negative control, one drop of
0.9% NaCl solution is used and the same procedure is repeated. In the case of
sensitization, a blister with a red court appears within 10–20 min at the site of the
immunogloblin whereas no such reaction occurs at the site of the negative control.
In this case, the heterologous immunoglobulin may only be used after desensitiza-
tion, for example by following one of the two alternative procedures recommended
by the American Academy of Pediatrics (American Academy of Pediatrics 2009):
via the intravenous route, 1:1,000 dilutions of the immunoglobulin are administered
with increasing volumes (0.1, 0.3 and 0.6 ml) followed by 1:100 and 1:10 dilutions
with the same escalating volumes and finally the undiluted immunoglobulin with
increasing volumes of 0.1, 0.3, 0.6 and 1.0 ml. The interval from injection to
injection is 15 min during which the patient is monitored closely for immediate
allergic reactions which – if serious in nature (generalized urticaria or arterial
hypotonia or dyspnoea) – require appropriate treatment and termination of the
desensitization procedure. The alternative procedure, with the same escalating
dilutions and volumes but sequentially switching from intradermal to subcutaneous
to intramuscular applications, is less preferable as it is less safe in terms of
standardization of the absorbed antigen content.
3 Disinfectants
Disinfectants are antimicrobial agents that are frequently used in medical settings
with the goal to reduce the load of pathogenic or facultative pathogenic
microorganisms (pathogens) on body surfaces (mainly hands) and objects in the
environment of patients or medical devices (Dettenkofer and Daschner 1997). The
ultimate goal of disinfection is to reduce the risk of transmission of pathogens from
patient to patient, health-care workers to patients, patients to health-care workers,
and objects or medical devices to patients. Usually, a reduction of 3–5 log of the
pathogens at the site of application (i.e., by 99.9–99.999%) is achieved by disinfec-
tion. In contrast to disinfection, sterilization describes the process of complete
elimination of pathogenic microorganisms.
Disinfection can be achieved by means of
• Heat
• Physical treatment
334 U. Heininger
• Chemical treatment
Heat is frequently used to disinfect heat-resistant objects. Before disinfection,
thorough cleaning is required to eliminate biologic (blood, phlegm, other
excretions) and non-biologic material. Afterwards, decontamination by residing
pathogens is achieved by exposing the objects to 75 C for at least 10 min. This
procedure can be standardized and programmed by use of disinfection machines.
Heat acts by disrupting membranes and denaturing proteins and nucleic acids.
Physical disinfection can be attempted by ultraviolet light at 260 nm. Applica-
tion of UV light leads to the formation of pyrimidine dimers in DNA which then
lead to genetic damage to cells. Theoretically, ultraviolet irradiation is an effective
method of reducing the amount of pathogens on surfaces and in the air, but it does
not penetrate glass. Its effect, however, is questionable among hygiene experts and
it is not frequently used.
Use of chemicals is the preferred method of disinfection in medical settings. The
properties, modes of action, advantages, disadvantages, and indications of
chemicals most widely used now or in the past are discussed here.
3.1 Alcohol
Alcohols (ethanol or isopropanol at concentrations of 50–80%, plus purified water)

are frequently used as a disinfectant on living tissue, mainly hands, and on nonliv-
ing surfaces. As alcohols evaporate quickly, there is only limited residual activity
resulting in short contact times. They are effective against a wide spectrum of
bacteria and lipid-enveloped viruses (e.g. hepatitis B and C, HIV). However,
alcohols have limited efficacy against non-enveloped viruses (e.g. rotavirus,
norovirus, enteroviruses, hepatitis A) and is ineffective against fungi and bacterial
spores.
3.2 Aldehydes
Aldehydes, such as formaldehyde and glutaraldehyde, have a broad disinfectious

activity (bacteria, viruses, fungi) and are also effective against bacterial spores.
They are partly inactivated by organic material and have only little residual activity.
They are mainly used for disinfection of non-living surfaces and medical devices
(e.g. endoscopes).
Of note, mycobacteria can be resistant against aldehydes.
3.3 Phenolics
Phenolics are active ingredients in some disinfectant soaps, e.g. used for
handwashing in medical settings. They are active against bacteria and fungi, but
not against bacterial spores and enveloped and non-enveloped viruses. Therefore,
they should only be used in combination with other disinfectants.
Due to their potential toxicity to sensitive individuals and also for reasons of
environment protection (toxicity to newborns, accumulation in water and food,
slow natural degradation) phenolics are less frequently used today than previously.
3.4 Quaternary Ammonium Compounds
Quaternary ammonium compounds, such as benzalkonium chloride, dimethyl-

distearyl-ammonium chloride, and cetylpyridinium chloride are surface active
compounds. Their spectrum of disinfection activity covers mainly gram-positive
bacteria whereas their activity against gram-negative bacteria, fungi, and viruses is
minimal or absent. This limits their usefulness in the clinical setting and usually
requires additional use of other disinfectants.
3.5 Oxidizing Agents
Oxidizing agents destroy the structure of cell membranes of microorganisms

leading to cell lysis. They have broad disinfection activity against bacteria, bacte-
rial spores, fungi, and enveloped and non-enveloped viruses. They are mainly used
for disinfection of laundry, medical devices and instruments.
Chloramine is mostly used for wound disinfection as is hydrogen peroxide.
3.6 Iodine
Povidone (PVP)-iodine preparations are used to disinfect skin and mucosal

surfaces, primarily in treatment and prophylaxis of wound infections. It is broadly
active against bacteria, bacterial spores, fungi, and enveloped and non-enveloped
viruses. Due to interference with the thyroid gland, PVP-iodine is contraindicated
in newborns and infants and in patients with thyroid gland dysfunction.
336 U. Heininger
References
Abdulla S, Oberholzer R, Juma O et al (2008) Safety and immunogenicity of RTS, S/AS02D

malaria vaccine in infants. N Engl J Med 359:2533–2544
American Academy of Pediatrics (2009) Passive immunization. In: Pickering LK, Baker CJ,
Kimberlin DW, Long SS (eds) Red book: 2009 report of the committee on infectious diseases,
28th edn. American Academy of Pediatrics, Elk Grove Village, IL
Black SB, Lewis E, Shinefield HR et al (2002) Lack of association between receipt of conjugate
haemophilus influenzae type B vaccine (HbOC) in infancy and risk of type 1 (juvenile onset)
diabetes: long term follow-up of the HbOC efficacy trial cohort. Pediatr Infect Dis J
21:568–569
Boland G, Beran J, Lievens M et al (2004) Safety and immunogenicity profile of an experimental
hepatitis B vaccine adjuvanted with AS04. Vaccine 23:316–320
Bonhoeffer J, Kohl K, Chen R et al (2002) The Brighton Collaboration: addressing the need for
standardized case definitions of adverse events following immunization (AEFI). Vaccine
21:298–302
Centers for Disease Control and Prevention (CDC) (2008) Invasive pneumococcal disease in
children 5 years after conjugate vaccine introduction–eight states, 1998–2005. MMWR Morb
Mortal Wkly Rep 57:144–148
Cooper CL, Davis HL, Morris ML et al (2004) CPG 7909, an immunostimulatory TLR9 agonist
oligodeoxynucleotide, as adjuvant to Engerix-B HBV vaccine in healthy adults: a double-blind
phase I/II study. J Clin Immunol 24:693–701
De Stefano F, Bhasin TK, Thompson WW, Yeargin-Allsopp M, Boyle C (2004) Age at first
measles-mumps-rubella vaccination in children with autism and school-matched control
subjects: a population-based study in metropolitan Atlanta. Pediatrics 113:259–266
De Wals P, Deceuninck G, Boulianne N, De Serres G (2004) Effectiveness of a mass immuniza-
tion campaign using serogroup C meningococcal conjugate vaccine. JAMA 292:2491–2494
Dettenkofer M, Daschner F (1997) Umweltschonende Sterilisation und Desinfektion. In: Daschner
F (ed) Praktische Krankenhaushygiene und Umweltschutz, 1st edn. Springer, Heidelberg
Didierlaurent AM, Morel S, Lockman L et al (2009) AS04, an aluminum salt- and TLR4 agonist-
based adjuvant system, induces a transient localized innate immune response leading to
enhanced adaptive immunity. J Immunol 183:6186–6197
Ellebedy AH, Webby RJ (2009) Influenza vaccines. Vaccine 27(Suppl 4):D65–D68
Gessner BD, Adegbola RA (2008) The impact of vaccines on pneumonia: key lessons from
Haemophilus influenzae type b conjugate vaccines. Vaccine 26(Suppl 2):B3–B8
Giannini SL, Hanon E, Moris P et al (2006) Enhanced humoral and memory B cellular immunity
using HPV16/18 L1 VLP vaccine formulated with the MPL/aluminium salt combination
(AS04) compared to aluminium salt only. Vaccine 24:5937–5949
Gr€uber C, Illi S, Lau S et al (2003) Transient suppression of atopy in early childhood is associated
with high vaccination coverage. Pediatrics 111:e282–e288
Guillaume L, Bath PA (2008) A content analysis of mass media sources in relation to the MMR
vaccine scare. Health Inform J 14:323–334
Heininger U (2003) Pr€avention von Pneumokokkeninfektionen. Monatsschr Kinderheilkd
151:391–396
Heininger U (2004) The success of immunization – shoveling its own grave? Vaccine
22:2071–2072
Hocine MN, Farrington CP, Touzé E et al (2007) Hepatitis B vaccination and first central nervous
system demyelinating events: reanalysis of a case-control study using the self-controlled case
series method. Vaccine 25:5938–5943
Ioannidis JPA, Lau J (2001) Completeness of safety reporting in randomized trials. An evaluation
of 7 medical areas. JAMA 285:437–443
Keitel W, Groth N, Lattanzi M et al (2010) Dose ranging of adjuvant and antigen in a cell culture
H5N1 influenza vaccine: safety and immunogenicity of a phase 1/2 clinical trial. Vaccine
28:840–848
Kohl KS, Gidudu J, Bonhoeffer J et al (2007) The development of standardized case definitions
and guidelines for adverse events following immunization. Vaccine 25:5671–5674
Kombo LA, Gerber MA, Pickering LK et al (2001) Intussusception, infection, and immunization:
summary of a workshop on rotavirus. Pediatrics 108(2):E37
Mutsch M, Zhou W, Rhodes P et al (2004) Use of the inactivated intranasal influenza vaccine and
the risk of Bell’s palsy in Switzerland. N Engl J Med 350:896–903
Pichichero ME (2008) Improving vaccine delivery using novel adjuvant systems. Hum Vaccin
4:262–270
Ruiz-Palacios GM, Guerrero ML, Bautista-Márquez A et al (2007) Dose response and efficacy of a
live, attenuated human rotavirus vaccine in Mexican infants. Pediatrics 120:e253–e261
Sacarlal J, Aide P, Aponte JJ et al (2009) Long-term safety and efficacy of the RTS, S/AS02A
malaria vaccine in Mozambican children. J Infect Dis 200:329–336
Sagara I, Ellis RD, Dicko A (2009) A randomized and controlled Phase 1 study of the safety and
immunogenicity of the AMA1-C1/Alhydrogel + CPG 7909 vaccine for Plasmodium
falciparum malaria in semi-immune Malian adults. Vaccine 27:7292–7298
Stehr K, Cherry JD, Heininger U et al (1998) A comparative efficacy trial in Germany in infants
who received either the Lederle/Takeda acellular pertussis component DTP (DTaP) vaccine,
the Lederle whole-cell component DTP vaccine or DT vaccine. Pediatrics 101:1–11
Stratton KR, Howe CJ, Johnston RB Jr (1994) Adverse events associated with childhood vaccines
other than pertussis and rubella. Summary of a report from the Institute of Medicine. JAMA
271:1602–1605
Tapiainen T, Bar G, Bonhoeffer J, Heininger U (2006) Evaluation of the Brighton Collaboration
case definition of acute intussusception during active surveillance. Vaccine 24:1483–1487
Vesikari T, Groth N, Karvonen A, Borkowski A, Pellegrini M (2009) MF59-adjuvanted influenza
vaccine (FLUAD) in children: safety and immunogenicity following a second year seasonal
vaccination. Vaccine 27:6291–6295
Postmarketing Surveillance
Vera Vlahović-Palčevski and Dirk Mentzer
Contents
1 General background . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 340
1.1 The Importance of Postmarketing Surveillance in Paediatric Practice . . . . . . . . . . . . . 340
1.2 Off-Label and Unlicensed Drug Use in Children . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 341
1.3 Orphan Drugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
2 Pharmacovigilance for Paediatric Medicines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 342
2.1 Pharmacovigillance for Off-Label and Unlicensed Drug
Use and Orphan Drugs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 343
2.2 Paediatric Formulation and Dosing Issues . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 344
2.3 Enhanced Spontaneous Reporting System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 345
2.4 Signal Detection Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 347
3 Legislation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 348
4 The Future . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 349
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 350
Abstract Postmarketing drug surveillance refers to the monitoring of drugs once

they reach the market after clinical trials. It evaluates drugs taken by individuals
under a wide range of circumstances over an extended period of time. Such
surveillance is much more likely to detect previously unrecognized positive or
negative effects that may be associated with a drug.
The majority of postmarketing surveillance concern adverse drug reactions
(ADRs) monitoring and evaluation. Other important postmarketing surveillance
components include unapproved or off-label drug use, problems with orphan drugs,
V. Vlahović-Palčevski (*)
Department for Clinical Pharmacology, University of Rijeka Medical School, University Hospital
Center Rijeka, Krešimirova 42, 51000 Rijeka, Croatia
e-mail: vvlahovic@inet.hr
D. Mentzer
Paul-Ehrlich-Institut, Referate Arzneimittelsicherheit, Paul-Ehrlich-Str. 51-59, 63225 Langen,
Germany

340 V. Vlahović-Palčevski and D. Mentzer
and lack of paediatric formulations, as well as issues concerning international

clinical trials in paediatric population.
The process of evaluating and improving the safety of medicines used in
paediatric practice is referred to as paediatric pharmacovigilance. It requires special
attention. Childhood diseases and disorders may be qualitatively and quantitatively
different from their adult equivalents. This may affect either benefit or risk of
therapies (or both), with a resulting impact on the risk/benefit balance. In addition,
chronic conditions may require chronic treatment and susceptibility to ADRs may
change throughout the patient’s lifetime according to age and stage of growth and
development. Therefore, paediatric pharmacovigillance aspects need to be tailored
to a number of variables based on heterogeneity of paediatric population. This
chapter will summarize and discuss the key issues.
Keywords (MeSH) Pharmacoepidemiology • Child • Drug Surveillance •

Postmarketing • Clinical Trial • Phase IV • Drug Approval • Off-label Prescribing •
Unlabeled Indication • Drug Formulation
1 General background
1.1 The Importance of Postmarketing Surveillance

in Paediatric Practice
Postmarketing drug surveillance refers to the monitoring of drugs once they reach
the market after three phases of clinical trials that are designed to test safety and
efficacy of drugs. Postmarketing drug surveillance using interventional or non-
interventional clinical trial aims to evaluate drugs taken by individuals under a wide
range of circumstances in real-world conditions over an extended period of time.
Such surveillance is much more likely to detect any undiscovered positive or
negative effects, which may be associated with a drug. Postmarketing drug surveil-
lance is critical to ensuring that a medication is safe for use by a wide variety
of people (i.e. varying ages, genders, races, lifestyles, etc.) under different
circumstances (i.e., people with comorbidities or on multiple drugs, with varying
nutritional status, taking over-the-counter supplements, etc.). The majority of
postmarketing surveillance encompasses adverse drug reaction (ADRs) monitoring
and evaluation.
Postmarketing surveillance in paediatric population denotes surveillance of
approved drugs used by persons aged 0–18. Many medicines are prescribed to
paediatric patients on an unlicensed or “off-label” basis because they have not been
adequately tested and/or formulated and authorized for use in appropriate paediatric
age group. Thus, additional important postmarketing surveillance components
involve unapproved or off-label drug use, problems with orphan drugs and lack
of paediatric formulations, the issues of conduction international clinical trials.
Postmarketing Surveillance 341
1.2 Off-Label and Unlicensed Drug Use in Children
The term off-label relates to the use of a medicine in a manner different from that
recommended by the manufacturers in their product license i.e., on a trial and error
basis. It may result either in benefit, no therapeutic effect, or adverse reaction.
The assumption that children with diseases or conditions similar to that of adults
respond similarly has perpetuated the use of medications approved in adults to treat
children, frequently without the appropriate studies in paediatric population. Only
one third of drugs used to treat children have been studied adequately in the
population in which they are being used and have appropriate use information on
the product label. For the other two thirds of drugs, information regarding safety
and efficacy for paediatric patients is insufficient or absent. The younger the
patient’s age group, the more likely the lack of information. It is estimated that
80–97% of infants in neonatal wards receive at least one off-label or unlicensed
drug (Pandolfini and Binati 2005; Grégoire and Finley 2007). Typically, labels for
new medications provide physicians with no guidance regarding a product’s effec-
tiveness, dosing or safety among paediatric patients. For most drug classes, there
exists almost no information on use in patients less than 2 years of age (Roberts
et al. 2003; Clark et al. 2006). The problem of off-label use is international and
affects hospitalized or non-hospitalized children. Those who administer drugs to
children are forced to deviate from the established labeling indications, for exam-
ple, by manipulating a drug’s formulation to obtain a “paediatric” dose (e.g.
splitting tablets into pieces), or by changing the indicated route of administration
(e.g. to avoid intramuscular injections in young patients) (Pandolfini and Binati
2005). Paediatric patients may also be deprived of potentially effective medication
because of the prescriber’s reluctance to use a medication for an off-label use.
Not all off-label drug use is inappropriate. A distinction should be made between
“well-founded” and “ill-founded” (disputable) off-label prescriptions. In contrast to
“ill-founded”, “well-founded” off-label prescriptions are recommended in clinical
practice guidelines or pharmcotherapeutic handbooks. These recommendations are
based on systematic examination of the published literature. The efficacy of “ill-
founded” off-label prescription is often questionable and adverse drug reactions and
unjustified healthcare costs may result (Gijsen et al. 2009).
Unlicensed is the use of drugs that do not have a product license, most often
those whose formulation is modified, that are prepared as extemporaneous
preparations, are imported or used before a license is granted, or that are chemicals
used for therapeutic purposes (Kimland et al. 2007). The reasons for a drug being
unlicensed in children are many. It occurs often because a drug has not been tested
in children, and this may be due to financial constraints or because of the apparent
difficulties with trial design and ethics of testing drugs in children.
The extent to which drugs are prescribed to children in an off-label manner vary
among different countries and settings. Data from UK suggest that in primary care
about 11% of drugs prescribed for children are used off-label (McIntyre et al. 2000).
In a retrospective cohort study analysing 1.74 million prescriptions in primary care
in Germany, 13% were found to be prescribed off-label (B€ucheler et al. 2002).

Similarly, another German study has shown that 87% of drugs prescribed to children
were prescribed in accordance with their license, but only 3% were rated as off-
label, and for the rest the licensing status could not be established within the drug
information supplied by the manufacturers (M€ uhlbauer et al. 2009). Higher figures
have been found in the Netherlands (29%) (‘tJong et al. 2002) and France (33%)
(Chalumeau et al. 2000). A survey on unlicensed and off-label drug use in paediatric
wards in European countries has shown that as much as 46% of drug prescriptions
were either unlicensed (39%) or off label (7%), and that 67% of patients received an
unlicensed or off-label drug prescription. The most common reason for off-label use
were that the medicine was prescribed at a different dose or frequency, in a different
formulation, or in an age group for which it had not been licensed (Conroy et al.
2000). Furthermore, neonatologists do not have another choice but to use drugs in
an unauthorized way because their patients are rarely entered into trials of new
preparations. Eighty percent of infants in an Australian neonatal intensive care unit
received an off-label or unlicensed preparation (O’Donnell et al. 2002).
1.3 Orphan Drugs
Orphan drugs are usually defined as drugs that have been abandoned or “orphaned”
by major drug companies. However, this definition can be extended to medications
that could be useful to a minority of population (i.e. orphan group), such as children,
physically or cognitively disabled patients, or the elderly if the medications were
available and approved for those groups.
According to European Medicines Agency (EMA), a medicinal product is
designated as an orphan medicinal product if: it is intended for the diagnosis,
prevention or treatment of a life-threatening or chronically debilitating condition
affecting no more than five in 10,000 persons in the European Union at the time of
submission of the designation application (prevalence criterion), or it is intended for
the diagnosis, prevention, or treatment of a life-threatening, seriously debilitating or
serious and chronic condition and without incentives it is unlikely that expected
sales of the medicinal product would cover the investment in its development, and
no satisfactory method of diagnosis, prevention, or treatment of the condition
concerned is authorized, or, if such method exists, the medicinal product will be
of significant benefit to those affected by the condition (EMA 2010, http://www.
ema.europa.eu, accessed 27 Jan 2010).
2 Pharmacovigilance for Paediatric Medicines
The purpose of postmarketing adverse drug event surveillance is to obtain informa-

tion on rare, latent, long-term adverse drug events or changes in drug-effect
frequencies not identified during premarket testing. However, knowledge of risks
associated with drug use in children is limited due to few paediatric drug safety
studies. At registration, little information on adverse drug reactions in children is
available since many drugs have not been tested in children. Risk–benefit analyses
of drugs for children are dependent on observations of adverse drug reactions and
effects from clinical use. The limited available information regarding adverse drug
events in paediatric population is based on medication errors such as overdosing or
accidental exposure (Fortescue et al. 2003; Kaushal et al. 2001). The potential for
adverse drug reactions among children is greater than that in adults. Young children
have immature metabolizing mechanisms, which decreases their ability to process
drugs and metabolites. In addition, drug doses must be adjusted individually for a
significantly broader range of body sizes and weights.
Paediatric pharmacovigilance is therefore the process of evaluating and improv-
ing the safety of medicines used in paediatric patients of all ages (Choonara 2006).
Most investigations concerning ADRs in children have focused on hospitalized
patients. In a meta-analysis of nine prospective studies among hospitalized children,
Impicciatore and colleagues calculated an overall incidence of ADRs of 9.5%, of
which 12.3% was regarded as severe. ADRs in hospitalized children require atten-
tion because they often involve serious illnesses, advanced drugs, and complicating
factors such as concomitant medication and comorbidity (Impicciatore et al. 2001).
However, ADRs outside the hospital should not be overlooked. Not only do many
children in primary care continue drug therapy that has been initiated in the hospital,
but also the number of drug-using children in primary care is much larger than the
number of hospitalized patients. Based on the few prospective studies, it has been
estimated that 1–1.5% of the drugs used by children outside the hospital result in an
ADR (Impicciatore et al. 2001; Sanz and Boada 1987; Cirko-Begovic et al. 1989). In
reported suspected paediatric adverse drug reactions (ADRs) in Sweden using data
from a nation-wide ADR reporting system during a period of 15 years, it was found
that the proportion of children suffering from a serious ADR was 13.0% and that for
drug related deaths was 0.14% (Kimland et al. 2005). In a report from the US, 6% of
the total ADR reports in a 5-year period concerned individuals aged less than 18
years (Johann-Liang et al. 2009).
2.1 Pharmacovigillance for Off-Label and Unlicensed Drug

Use and Orphan Drugs
Off-label and unlicensed drug use in children has resulted in questions to drug
information centers and has been reported to be extensive, and, as reported, has
resulted in an increased risk of adverse drug reactions. A French study that involved
more than 1,400 children has shown that 42% of outpatients were exposed to at
least one off-label prescription, and the incidence of adverse drug reactions was 1.4
in the whole population and 2.0% in patients exposed to at least one off-label
prescription (Horen et al. 2002). An observational analysis of spontaneous adverse
drug reaction reported in 1 year in Sweden investigated the extent and

characteristics of off-label prescribing for paediatric outpatients among drugs
reported to have caused an adverse reaction. Of all the adverse reactions, 42.4%
were related to the use of drugs that had been prescribed outside the terms of the
product licence. It was more frequently associated with serious than non-serious
ADRs and mostly due to a non-approved age or dose (Ufer et al. 2004).
Orphan drugs must go through the same development process as any other drug
and must be shown to meet the same standards for effectiveness and safety as a drug
for a common condition. Indeed, because of the small number of patients available
to be enrolled in clinical trials of orphan drugs, these products must be even
more effective than the average drug if a statistically significant benefit is to be
established. Since 85–90% of known rare diseases are serious or life threatening,
patients and physicians may be willing to accept a slightly higher level of risk than
they would from a treatment for a less serious disease. But the limited number of
patients plays a role here as well: although there have been no reports of serious
adverse reactions to any orphan drugs thus far, when a product is tested in a very
small population, our knowledge of the safety profile may not be complete as it can
be for a treatment for a more prevalent condition (Haffner 2006).
2.2 Paediatric Formulation and Dosing Issues
Today’s standards of clinical drug development require clinical trials enrolling

several hundred patients, which is in general not practical or possible in a paediatric
population. Therefore, drugs are not adequately tested and labeled in children with
regard to dosing and formulation, especially not in very young children (Nunn and
Williams 2005). Additional constraints may be seen in low prevalent diseases and
varying patient phenotypes (e.g. neurometabolic disease).
Incorrect dosing, under- as well as over-dosing, and use of products with
improvised formulations or inappropriate drug concentration are known to be
responsible for ADRs (Horen et al. 2002; Turner et al. 1999).
Additional problems may arise, if there is a poor knowledge about validity of
laboratory parameters and values of diagnostic and clinical endpoints in a clinical
trial.
Besides the challenges with logistic and organisation of a clinical trial, special
physiology of maturing organs needs to be considered for dose-finding studies as
well as for the development of an age appropriate formulation (Kearns et al. 2003).
For instance, much higher extracellular fluid volume, especially in premature
babies as compared to full-term infants, older infants or adults is an important
example of the need for thorough investigation of the pharmacokinetics of drugs.
Conversely, fat content is lowest in premature babies, higher in neonates and even
higher in infants and this has to be considered when applying doses on an mg/kg
body weight basis to achieve plasma concentrations similar to those of adults.
Further on, an initial loading dose may be necessary as a part of the treatment
regimen, the dosage interval may need to be increased and the total dose decreased
depending on hepatic and renal function. For medicines that are cleared by liver,
they may have a longer plasma half-life and thus a longer time to reach steady state.
Similarly, for medicines that are entirely eliminated through kidneys, the greater the
prematurity, the less are the kidneys able to excrete the substance and consequently
the longer will be the half-life.
The lack of reliable pharmacokinetic and pharmacodynamic data in paediatric
populations deriving from systematic drug development and clinical trials are
claimed to be responsible for some complications and difficulties following treat-
ment in paediatric population. In most cases it has been related to missing informa-
tion on the right dose and appropriate formulation. These deficiencies need to be
reflected according to each of the different age subpopulations in paediatrics in
order to strive toward safer medicines for children (Hartford et al. 2006; Interna-
tional Conference on Harmonisation 2000).
Where unlicensed and off-label paediatric use is common, it is important for
both the marketing authorization holder and the regulatory authorities to monitor
for any consequential safety concerns and to take appropriate measures to address
them and include in the Summary of Product Characteristics as a standard risk
minimisation measure. The reasons for a relative or absolute contraindication
should also be presented in the product information leaflet to appropriately com-
municate the risk of off-label use (WHO 2007).
2.3 Enhanced Spontaneous Reporting System
The major concern with ADRs is for serious adverse reactions, which are often rare,
and will generally not be observed in paediatric clinical trial programme, particu-
larly if there is a latent period before the onset or a trigger such as change in growth
or development (Impicciatore et al. 2001). Some serious ADRs may only be
diagnosed in a distinct age subgroup of paediatric population (e.g. febrile convul-
sion, growth retardation). Taking this into account, collection and extrapolation of
safety data in paediatric population from data in adults is not always possible due to
physiological facts such as metabolism, growth, and mental development.
Therefore, routine pharmacovigilance measures for detecting new safety signals
with extensively used drugs in adults may be much less effective in paediatric
population. A different, more proactive, approach is needed to conduct pharmacov-
igilance for these types of low usage products.
Clinical trial protocols should set out actions to be taken and their timing, by
category of ADR, if it occurs. For example, if a serious ADR is suspected, a blood,
saliva or urine sample (as appropriate) should be taken as soon as possible after the
suspected event. Preferably the samples should be frozen for drug and metabolite
measurement. For postauthorization safety studies, similar provisions might be
appropriate, but then it needs to be understood that including such a provision in
a trial protocol would disqualify it from having non-interventional status.
Special consideration should be given to long-term follow up as the susceptibility

to ADRs may change throughout the patient’s lifetime according to age and the
stage of growth and development. This applies especially to chronic conditions,
which may require long term, or even life-long, treatment. ADRs related to the
central nervous system are often of critical importance in this respect. Open
questions concerning long-term safety may be answered by results from additional
animal studies, such as juvenile animal toxicology studies. Mutagenicity and carci-
nogenicity data are also important and may need further scientific investigation
through juvenile animal studies (EMA 2005). However, the predictive value of such
studies in terms of subsequent effects in paediatric population is currently unknown.
Disease databases and registries as well as active surveillance systems and
enhanced reporting may help to monitor event rates. Furthermore, specialist
networks and paediatric clinical trial networks may be equally useful in this
context.
Several methods have been used to encourage and facilitate reporting by
healthcare professionals in different situations, such as in-hospital settings for
new products or for limited time periods. Such methods include online reporting
of adverse events and systematic enhanced reporting of adverse events based on
predefined criteria. While these methods have been shown to improve reporting, the
limitations of passive surveillance, especially selective reporting, are well known
(Haffner et al. 2005; Neubert et al. 2006).
Active surveillance, in contrast to passive surveillance, seeks to ascertain
completely the number of adverse events via continuous pre-organized process.
An example of active surveillance is a follow-up of patients treated with a particular
drug through a risk management program. In general, it is more feasible to get
comprehensive data on individual ADR reports through an active surveillance
system than through a passive reporting system. Elaborating surrogate parameters
and indicator symptoms for adverse reactions is useful to establish specific case
definitions for adverse drug reactions in children (Wong and Murray 2005).
In this respect, different categories of ADRs may need different methods for
detection. Routine pharmacovigilance is predominantly based on spontaneous
reporting, but other methods may be considered depending on the estimated
frequency of the expected ADRs (Table 1) (Meyboom et al. 1997).
To provide evidence-based evaluation of relative frequency of adverse drug
reactions or incidence associated with a disease in relation to drug administration,
pharmaco-epidemiological studies should be performed. To establish a causal
association between treatment and ADR, cohort or case–control studies may be
considered; these have been established in adult postmarketing safety studies.
Epidemiological studies using patient databases have been helpful for collecting
information on the incidence of a specific event in general population and may be
useful for increasing knowledge of particular safety issues (Garcia Rodriguez and
Perez Gutthann 1998).
In cases where safety issue is predictable, for example, based on preclinical
findings, long-term follow up registries or long-term cohort studies should be
considered.
Table 1 Methods to detect ADRs

Methods Frequency of reaction
( ) No relevance > 1/
(+) Possible supportive 10–1/ 1/100–1/ 1/1,000–1/ 1/5,000–1/ 1/10,000–1/ <1/
(++) Supportive 100 1,000 5,000 10,000 50,000 50,000
Spontaneous reporting
(international) + ++ ++ ++ ++ +/
Intensified monitoring + ++ ++ +
Prescription event
monitoring + ++ ++ +
Case–control studies + ++ ++
Post-marketing
surveillance studies + ++ +
Large data resources
(+record linkage) ++ ++ + +
Clinical trials ++ +
As detection and monitoring of ADRs is very much depending on the concerned

paediatric age groups, it is necessary that specific pharmacovigilance plans,
strategies and activities should be tailored accordingly. For example, small children
are less able to communicate their complaints verbally and the relevant information
concerning ADRs is mainly dependent on the interpretation of their behavior by the
parents or healthcare professionals Therefore, the need for an enhanced pharmacov-
igilance approach in paediatric pharmacovigilance appears more appropriate.
2.4 Signal Detection Methods
By definition a drug safety signal may arise from a previously unrecognized safety
issue, a change in the frequency or severity of a known safety issue or identification
of a new at risk group. These aspects are all relevant in paediatric population and
both Marketing Authorisation Holder and regulatory authorities are responsible for
identifying these kinds of signals.
Signal detection and data mining in paediatric population are dependent on
detection methods used which needs to be effective for small populations and low
numbers of possible cases. Enhanced data capture techniques can increase the
completeness and quality of the information obtained (Bate et al. 1998; Evans
et al. 2001).
Signal detection should include appropriate stratification for the data collected
based on specific needs (for example by age group or specific medicines like
vaccines), as this can be helpful to increase the ability to detect signals from
spontaneous databases. However, signal detection is an evolving field and the
most up-to-date and suitable statistical methods should be considered based on
the content of the data and the size of database used (Evans 2008).
The review and interpretation of results coming from signal detection analyses
should be at a high and cautious level of suspicion and should have an emphasis on
follow-up to obtain essential information before coming to a final conclusion. Even
one case report may be enough to trigger further investigation or risk minimisation
measures.
In paediatric drug development, the age-related physiological aspects should not
only be considered when conducting clinical trials in children and adolescence as it
is routine for efficacy-related objectives, but they are also very important for signal
detection methods and monitoring of the safety aspect of the product once used in
children.
Given these limitations every opportunity should be taken to maximise the
information obtained following the occurrence of an ADR during the paediatric
development programme.
3 Legislation
Guidance for paediatric pharmacovigilance has recently been emerging. European

Medicinal Agency (EMA; former European medicines Evaluation Agency, EMEA)
has an entire guidance dedicated to safety-monitoring concepts for paediatric
indications in which it is recognised that susceptibility to ADRs with chronic
treatment may change throughout a patient’s lifetime. It includes a particular
focus upon aspects of growth and development. This guidance also recognises
that in most cases clinical trials provide limited data regarding safety because of
limited patient exposure which makes it difficult to detect rare or delayed events,
and therefore it is important to conduct long-term follow up.
New legislation governing the development and authorisation of medicines for
use in children aged 0–17 years was introduced in the European Union in January
2007. The new piece of legislation – Regulation (EC) No 1901/2006 as amended
(the “Paediatric Regulation”) – introduces sweeping changes into the regulatory
environment for paediatric medicines, designed to better protect the health of
children in the EU. The Paediatric Regulation also brings in many new tasks and
responsibilities for the European Medicines Agency, chief of which is the creation
and operation of a Paediatric Committee within the Agency to provide objective
scientific opinions on any development plan for medicines for use in children.
In 1997, the United States Congress passed the Food and Drug Administration
Modernization Act (FDAMA), which encourages studies of certain therapies being
used in paediatrics by providing an exclusivity incentive provision.
In 1998 came the Pediatric Rule, a mandatory regulation that requires paediatric
studies for those conditions being studied in adults and in which significant use or
benefit in paediatrics was expected (Regulations required manufacturers to assess
the safety and effectiveness of new drugs and biological products in paediatric
patients. 63 Federal Register. 66631 (1998). The Best Pharmaceuticals for Children
Act, enacted 4 January 2002, renewed the paediatric exclusivity provision. It aimed
to amend the Federal Food, Drug, and Cosmetic Act to improve the safety and
efficacy of pharmaceuticals for children (Best Pharmaceuticals for Children Act.
Pub L No. 107–109). A fund was created for research and studies on older products
devoid of commercial interest. This fund is managed by the National Institutes of
Health (NIH) and the Food and Drug Administration (FDA). On 17 October 2002,
the Pediatric Rule was enjoined. As a consequence, the Pediatric Research Equity
Act of 2003 became a law on 3 December 2003. This Act gave the FDA the
authority to require certain research into drugs used in paediatric patients. On
September 27, the Food and Drug Administration Amendments Act of 2007, was
signed. Among the many components of the law, the Best Pharmaceuticals for
Children Act (BPCA) and the Pediatric Research Equity Act (PREA) were
reauthorized. Both of these are designed to encourage more research into, and
more development of, treatments for children. They cover many issues including
the need to strengthen surveillance of adverse events and to define the role of the
Paediatric Advisory Committee which now bears the requirement to review all
paediatric safety data at least 1 year post approval.
In a meeting on June 14–15, 2007, the US Food and Drug Administration
(FDA), the European Commission (EC), and the European Medicines Agency
(EMEA) have agreed to expand their current cooperative activities in several
important areas, in particular paediatrics (http://www.ema.europa.eu/htms/human/
paediatrics/).
4 The Future
As the biological sciences have evolved, pharmacovigilance has slowly shifted

toward earlier, proactive consideration of risks and potential benefits of drugs in the
pre- and post-approval stages of drug development.
Since the introduction of the EU paediatric regulation in January 2007, the
development and the life cycle of a drug in the pre- and post-authorization periods
have changed significantly. Pharmacovigilance science has traditionally been a
discipline focused on the post-marketing or post-authorization period, in particular
with attention directed toward pre-clinical safety data, clinical trials, and adverse
events. In this respect, the central function in this EU paediatric regulation, the
paediatric investigation plan, plays an additional important role for the survey of
drug safety in paediatrics.
Despite the new activity of drug development in paediatrics the particular
emphasis on monitoring off-label use, medication errors and reports of poisoning
needs to continue, as still a large number of established drugs, not jet authorized for
the paediatric population, are used. If important safety information relating to off-
label use becomes available, this should be included in the Summary of Product
Characteristics as a standard risk minimisation measure.
Special consideration should be given to the need for long-term follow up, for
example, through treatment registries, including possible effects on skeletal, neural,
behavioral, sexual, and immune maturation and development. Specific proposals

for prospective monitoring will depend on the size of the target population and
expected incidence of ADRs (if available).
The development of drugs for the paediatric population has changed the aware-
ness that both safety and efficacy need to be thoroughly investigated for safe
treatment of children. In conjunction with the knowledge about efficacy, pharma-
cokinetics, pharmacodynamics and the age-appropriate formulation for the
concerned drug, the impact on the objective of making available safe medicines
for children will steadily improve. Under the umbrella of the proposal for safer
medicines for children, a joint effort is needed to carry out clinical research and
appropriate drug development.
References
Bate A, Lindquist M, Edwards IR (1998) A Bayesian neural network method for adverse drug
reaction signal generation. Eur J Clin Pharmacol 54:315–321
B€ucheler R, Schwab M, M€ orike K et al (2002) Off label prescribing to children in primary care in
Germany: retrospective cohort study. BMJ 324:1311–1312
Chalumeau M, Treluyer J, Salanave B et al (2000) Off label and unlicensed drug use among
French office based paediatricians. Arch Dis Child 83:502–505
Choonara I (2006) Paediatric pharmacovigilance. Paed Perinat Drug Ther 7:50–53
Cirko-Begovic A, Vrhovac B, Bakran I (1989) Intense monitoring of adverse drug reactions in
infants and preschool children. Eur J Clin Pharmacol 36:63–65
Clark RH, Bloom BT, Spitzer AR et al (2006) Reported medication use in the neonatal intensive
care unit: data from a large national data set. Paediatrics 117(6):1979–1987
Conroy S, Choonara I, Impicciatore P et al (2000) Survey on unlicensed and off label drug use in
paediatric wards in European countries. BMJ 320:79–82
European Medicines Agency. Guideline on the need for non-clinical testing in juvenile animals of
pharmaceuticals for paediatric indication (EMEA/CHMP/SWP/169215/2005), published
24.01.2008
European Medicines Agency. Medicines for children. http://www.ema.europa.eu/pdfs/human/
comp/29007207en.pdf. Accessed 27 Jan 27 2010
Evans SJW (2008) Stratification for spontaneous report databases. Drug Saf 31(11):1049–1053
Evans SJW, Waller PC, Davis S (2001) Use of proportional reporting ratios (PRRs) for signal
generation from spontaneous adverse drug reaction reports. Pharmacoepidemiol Drug Saf
10(6):483–486
Fortescue EB, Kaushal R, Landrigan CP et al (2003) Prioritizing strategies for preventing
medication errors and adverse drug events in paediatric inpatients. Paediatrics 111:722–729
Garcia Rodriguez LA, Perez Gutthann S (1998) Use of the UK general practice research database
for pharmacoepidemiology. Br J Clin Pharmacol 45:419–425
Gijsen R, Jochemsen H, vanDijk L et al (2009) Frequency of ill-founded off-label prescribing in
Dutch general practice. Pharmacoepidemiol Drug Saf 18:84–91
Grégoire MC, Finley A (2007) Why were we abandoned? Orphan drugs in paediatric pain.
Paediatr Child Health 12(2):95–96
Haffner ME (2006) Adopting orphan drugs – two dozen years of treating rare diseases. N Engl J
Med 354:445–447
Haffner S, von Laue N, Wirth S et al (2005) Detecting adverse drug reactions on paediatric wards:
intensified surveillance versus computerised screening of laboratory values. Drug Saf
28(5):453–464
Hartford CG, Petchel KS, Mickail H et al (2006) Pharmacovigilance during the pre-approval
phases: an evolving pharmaceutical industry model in response to ICH E2E, CIOMS VI, FDA
and EMEA/CHMP risk-management guidelines. Drug Saf 29(8):657–673
Horen B, Montastruc JL, Lapeyre-Mestre M (2002) Adverse drug reactions and off-label drug use
in paediatric outpatients. Br J Clin Pharmacol 54:665–670
Impicciatore P, Choonara I, Clarkson A et al (2001) Incidence of adverse drug reactions in
paediatric in/out-patients: a systemic review and meta-analysis of prospective studies. Br J
International Conference on Harmonisation (ICH) (2000) Topic E 11: clinical investigation of
medicinal products in the paediatric population. http://www.europa.emea.eu./pdfs/human/ich/
271199EN.pdf
Johann-Liang R, Wyeth J, Chen M et al (2009) Paediatric drug surveillance and the food and drug
administration’s adverse event reporting system: an overview of reports, 2003–2007.
Pharmacoepidemiol Drug Saf 18:24–27
Kaushal R, Bates DW, Landrigan C et al (2001) Medication errors and adverse drug events in
paediatric inpatients. JAMA 285:2114–2120
Kearns GL, Abdel-Rahman SM, Alander SW et al (2003) Developmental pharmacology–drug
disposition, action, and therapy in infants and children. N Engl J Med 349(12):1157–1167
Kimland E, Rane A, Ufer M et al (2005) Paediatric adverse drug reactions reported in Sweden
from 1987 to 2001. Pharmacoepidemiol Drug Saf 14:493–499
Kimland E, Bergman U, Lindemalm S et al (2007) Drug related problems and off-label drug
treatment in children a seen at a drug information centre. Eur J Pediatr 166:527–532
McIntyre J, Conroy S, Avery A et al (2000) Unlicensed and off-label prescribing of drugs in
general practice. Arch Dis Child 83:498–501
Meyboom RH, Egberts AC, Edwards IR et al (1997) Principles of signal detection in pharmacov-
igilance. Drug Saf 16(6):355–365
M€ uhlbauer B, Janhsen K, Pichler J et al (2009) Off-label use of prescription drugs in childhood and
adolescence. Dtsch Arztebl Int 106(3):25–31
Neubert A, Dormann H, Weiss J et al (2006) Are computerised monitoring systems of value to
improve pharmacovigilance in paediatric patients? Eur J Clin Pharmacol 62(11):959–965
Nunn T, Williams J (2005) Formulation of medicines for children. Br J Clin Pharmacol
59(6):674–676
O’Donnell CP, Stone RJ, Morley CJ (2002) Unlicensed and off-label drug use in an Australian
intensive care unit. Paediatrics 110:e52
Pandolfini C, Binati M (2005) A literature review on off-label drug use in children. Eur J Pediatr
164:552–558
Roberts R, Rodriguez W, Murphy D et al (2003) Paediatric drug labeling. Improving the safety and
efficacy of pediatrc therapies. JAMA 290(7):905–911
Sanz E, Boada J (1987) Adverse drug reactions in paediatric outpatients. Int J Clin Pharmacol Res
7:169–172
‘tJong GW, Eland IA, Strukenboom MC et al (2002) Unlicenced and off-label prescription of
drugs to children: population based cohort study. BMJ 324:1313–1314
Turner S, Nunn AJ, Fielding K et al (1999) Adverse drug reactions to unlicensed and off label
drugs on paediatric wards: a prospective study. Acta Paediatr 88(9):965–968
Ufer M, Kimland E, Bergman U (2004) Adverse drug reactions and off-label prescribing for
paediatric outpatients: a one-year survey of spontaneous reports in Sweden. Pharmacoe-
pidemiol Drug Saf 13:47–152
Wong I, Murray ML (2005) The potential of UK clinical databases in enhancing paediatric
medication research. Br J Clin Pharmacol 59(6):750–755
World Health Organization Guideline (2007) Promoting safety of medicines for children. www.
who.int/medicines/publications/essentialmedicines/Promotion_safe_med_childrens.pdf
Global Aspects of Drug Development
Kalle Hoppu and Hans V. Hogerzeil
Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
2 Meeting the Health Needs of Children Around the World . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 354
3 The Concept of Essential Medicines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 355
4 WHO Essential Medicines List for Children . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 358
5 Developing Appropriate Paediatric Formulations for the Different Environments . . . . . 359
6 Accounting for Sociocultural Differences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 360
7 Paediatric Fixed-Dose Combinations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
8 The New Paradigm for Global Paediatric Formulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 361
9 Simplified Dosage Regimens Needed: Without Compromising Safety and Efficacy . . 363
10 Paediatric Clinical Trials in the Developing World . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 364
10.1 Ethical Aspects of Clinical Trials in the developing world . . . . . . . . . . . . . . . . . . . . . . 365
10.2 Scientific Aspects of Paediatric Clinical Trials in Developing World . . . . . . . . . . . 366
11 Price, Quality, and Access . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 366
11.1 Providing Access to Essential Medicines for Children at Country Level . . . . . . . 367
11.2 Quality: A Major Challenge . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
11.3 Medicines Have to Be Affordable . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 368
12 Rational Use of Medicines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
13 National Medicine Policy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 369
14 Public Health Approach to Innovation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 370
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 371
K. Hoppu (*)
Poison Information Centre, Helsinki University Central Hospital and Hospital for Children and
Adolescents, Institute for Clinical Sciences, University of Helsinki, P.O. Box 790 (Tukholmankatu
17), 00029 HUS (Helsinki), Finland
e-mail: kalle.hoppu@hus.fi
H.V. Hogerzeil
Essential Medicines and Pharmaceutical Policies, World Health Organization, 1211 Geneva 27,
Switzerland

354 K. Hoppu and H.V. Hogerzeil
Abstract About nine million children die every year before they reach the age of
5 years, of conditions largely amendable with existing medicines. Lack of medicines
is not the single most important health problem of children, but work to provide
children with better access to appropriate medicines is essential for achievement
of the child health goals set. Taking into consideration the global aspect in
the development of paediatric medicines the benefits of the regional paediatric
initiatives can be spread worldwide. This chapter provides insights in the challenges
and opportunities of developing paediatric medicines for health needs of children in
the developing world. The Essential Medicines List for children first made available
in 2008 serves as an example of the many tools available from WHO to improve
children’s access to the medicines they need.
Keywords Drug development • Essential medicines • Access to medicines •

Quality of medicines • Clinical trials • WHO • Ethics • Developing world • Children
1 Introduction
About 28% of the 2008 world population of 6.7 billion is of less than 15 years of
age. In less developed countries children and adolescents less than 15 years of age
make out about a third, and in the sub-Saharan Africa about 43% of the population.
The trend in childhood mortality has been favourable on the global level and
contributes to the increase in life expectancy. However, many countries still have
high child mortality, particularly in sub-Saharan Africa and South Asia, and in
recent years made little or no progress in reducing the number of child deaths.
While lack of medicines is not the single most important health problem of
children, it is clear that work to provide children with better access to appropriate
medicines is essential for achievement of the child health goals set, like the
Millennium Development Goals (MDG) – MDG 4 (Reduce child mortality by
two thirds) and MDG 6 (combat HIV/AIDS, malaria, and other major diseases).
The paediatric medicines initiatives launched in the US and the EU, in essence
public health interventions to improve child health, have successfully increased
interest in study and development of paediatric medicines and already led to
positive results. However, the increased research and development of paediatric
medicines initiated by these regional initiatives are unlikely to benefit children of
the less developed world unless their special needs and requirements are considered
in the process. The aim of this chapter is to discuss factors to be considered,
challenges but also opportunities of developing paediatric medicines that meet
the needs of children in less developed world.
2 Meeting the Health Needs of Children Around the World
It is estimated that about nine million children die every year before they reach the
age of 5 years, 70% of them from treatable conditions. More than three million die
in the neonatal period. The main causes of death in the first month are preterm birth,
Global Aspects of Drug Development 355
birth asphyxia, and infections. After the age of one month and up until the age of
five, the main causes of death are pneumonia (approximately two million/year),
diarrhoeal diseases (approximately 1.9 million/year, comprising 18% of all
under-five deaths), malaria (estimated one million/year), measles, and HIV/AIDS.
Malnutrition contributes to more than one third of under-five deaths.
Effective interventions in the form of medicines exist for many of these
conditions, but a significant proportion of the children do not have access to
these medicines. Like even in the richest countries of the world, the medicines
available for children are often not appropriate for their needs. Many of the
medicines that do exist do not exist in appropriate formulations for children. A
recent study on the inclusion of key medicines for children in national essential
medicines lists (EMLs) and standard treatment guidelines, and to assess the avail-
ability and cost of these medicines in 14 countries in central Africa found that
the availability of key essential medicines for children was poor (Robertson
et al. 2009).
Making medicines available, medicines supply, is part of a functioning health
care system. Most health programmes depend on access to affordable medicines;
without quality medicines success is not possible. Recognizing that better access to
medicines is a prerequisite for improving health outcomes in children, in May 2007
the World Health Assembly passed Resolution WHA60.20 “Better Medicines for
Children”, which identified key steps for ensuring better medicines for children
(World Health Assembly 2007). Key points of the Resolution are summarized in
Table 1.
The WHA60.20 resolution set goals and called for action by Member States and
WHO to address the global need for children’s medicines. One important target for
action was the WHO Model List of Essential Medicines (EML), a global standard
for 30 years, used by many countries as a model for national lists to guide drug
procurement and supply. Although this list has included some paediatric medicines,
a children’s list had not been systematically developed.
3 The Concept of Essential Medicines
Essential medicines are those that satisfy the priority health care needs of the
population. They are selected on the basis of disease prevalence, evidence on
efficacy, safety and comparative cost-effectiveness. The selection of essential
medicines is one of the core principles of a national medicine policy because it
helps to set priorities for all aspects of the pharmaceutical system. This is a global
concept, which can be applied in any country, in private and public sectors and at
different levels of the health care system.
There is good evidence that clinical guidelines and essential medicines lists,
when properly developed, introduced and supported, improve prescribing quality
and lead to better health outcomes (Grimshaw and Russell 1993; Kafuko and
Bagenda 1994; Woolf et al. 1999; Laing et al. 2001). But there is also an economic
Table 1 Key points of the World Health Assembly resolutionWHA60.20 on Better medicines for
children
WHA60.20 urges member states:
To take steps to identify appropriate dosage forms and strengths of medicines for children, and
to encourage their manufacture and licensing
To encourage research and development of appropriate medicines for diseases that affect
children, and to ensure that high-quality clinical trials for these medicines are conducted in an
ethical manner
To facilitate timely licensing of appropriate, high-quality and affordable medicines for children
and innovative methods for monitoring the safety of such medicines
To encourage the marketing of adequate paediatric formulations together with newly developed
medicines
To promote access to essential medicines for children through inclusion, as appropriate, of those
medicines in national medicine lists, procurement and reimbursement schemes, and to devise
measures to monitor prices
To collaborate in order to facilitate innovative research and development on, formulation of,
regulatory approval of, provision of adequate prompt information on, and rational use of,
paediatric medicines and medicines authorized for adults but not approved for use in children
WHA60.20 requests the WHO director-general
To promote the development, harmonization, and use of standards for clinical trials of
medicines for children
To revise and regularly update the Model List of Essential Medicines in order to include missing
essential medicines for children
To ensure that all relevant WHO programmes, including but not limited to that on essential
medicines, contribute to making safe and effective medicines as widely available for children
as for adults
To promote the development of international norms and standards for quality and safety of
formulations for children, and of the regulatory capacity to apply them
To make available evidence-based treatment guidelines and independent information on dosage
and safety aspects of medicines for children, and to work with Member States in order to
implement such guidelines
argument. First, in developing countries pharmaceuticals are the second biggest

budget line in the health system, after salaries. Secondly, new essential medicines
are expensive. For example, even with good differential pricing lumefantrine-
artemisinine at the time of its introduction for use in developing countries was
20 times more expensive than chloroquine, the first-line antimalarial it is supposed
to replace; atovaquone-proguanil is about 400 times as expensive. Life-saving
antiretroviral combinations cost $80–100 per year while 38 countries have less
than $2 per person per year available for all their medicine needs. The selection of
new essential medicines for public supply, subsidy or reimbursement has enormous
financial implications for developing countries.
The advantages of limited lists are therefore both medical and economical. From
a medical point of view they lead to better quality of care and better health
outcomes and help focus quality control, drug information, prescriber training
and medical audit. Economically they lead to better value for money, to lower
costs through economies of scale and to simplified systems of procurement, supply,
distribution and reimbursement. All of this is even more important in resource-poor
situations where the availability of medicines in the public sector is often erratic.
Under such circumstances measures to ensure a regular supply of essential
medicines will result in real health gains and in increased confidence in the health
services.
The concept of essential medicines was launched in 1977 with the publication of
the first WHO Model List of Essential Medicines. Since then the List was revised
every 2 years. Both its content and the process by which it is updated are intended as
a model for developing countries. In 2002, WHO completed a rigorous overhaul of
the process to update the list. An important change was that affordability changed
from a precondition into a consequence of the selection. For example, before 2002
effective but expensive medicines, such as single-dose azithromycin for trachoma,
were not listed because of their price. The new definition of essential medicines is:
Essential medicines are those that satisfy the priority health care needs of the population.
They are selected with due regard to disease prevalence, evidence on efficacy and safety,
and comparative cost-effectiveness. Essential medicines are intended to be available within
the context of functioning health systems at all times, in adequate amounts, in the appro-
priate dosage forms, with assured quality, and at a price the individual and the community
can afford. The implementation of the concept of essential medicines is intended to be
flexible and adaptable to many different situations; exactly which medicines are regarded as
essential remains a national responsibility (WHO 2003)
Under the new definition, twelve antiretroviral medicines for HIV/AIDS were
listed, irrespective of their high cost at that time. Their listing implied that these
medicines should become affordable to all patients who need them; and seven years
later we can conclude that prices have indeed come down dramatically.
Within a country, market approval of a pharmaceutical product is usually
granted on the basis of efficacy, safety and quality, and rarely on the basis of a
comparison with other products already on the market, or cost. This regulatory
decision defines the availability of a medicine in the country. In addition, most
public drug procurement and insurance schemes have mechanisms to limit procure-
ment or reimbursements of drug costs. For these decisions, an evaluation process is
necessary, based on a comparison between various drug products and on
considerations of value for money. This second step leads to a national list of
essential drugs.
A list of essential drugs is best developed for different levels of care, and on the
basis of standard treatment guidelines for common diseases and complaints that can
and should be diagnosed and treated at that level. National lists of essential
medicines are used to guide the procurement and supply of medicines in the public
sector, reimbursement schemes, medicine donations and local medicine production;
they also help define the training of health workers. In short, essential medicines
lists provide the scientific and public health basis for focus and expenditure in the
pharmaceutical sector.
In many countries it has taken several years and several editions of treatment
guidelines and lists of essential medicines before a more or less stable product was
developed which was accepted by most prescribers and actually used for training,
procurement and supply. Although time-consuming, the wide involvement of a
large number of prescribers, academic departments, health facilities and profes-

sional organizations is crucial. It is also important to stress the point that essential
medicines are not second-rate medicines for poor people, but that they represent the
most cost-effective treatments for a given condition. Over time, prescribers increas-
ingly begin to recognize and trust the value of the clinical guidelines.
At the turn of the century, over 150 countries had official essential medicines
lists, of which 127 had been updated in the previous 5 years. Most developing
countries have national lists and some have provincial or state lists as well.
Many international organizations, including UNICEF and UNHCR, as well as
non-governmental organizations and international non-profit supply agencies,
have adopted the essential medicines concept for their supply systems. Several
developed countries, such as Australia, also use the same approach.
4 WHO Essential Medicines List for Children
Effective treatments exist for many of the priority diseases and conditions of
children, however many of these essential medicines do not exist in formulations
for children. There are many gaps in evidence and knowledge about the use of
existing medicines in children and in identifying what medicines do not exist. The
development of the first WHO Essential Medicines List for children (EMLc) in
2007 was a first step in addressing this knowledge gap.
The first EMLc (WHO 2008a), which was adopted on the day of the 30th
Anniversary of the EML, was developed using the same procedures that are used
to update the main list. Selection of medicines as essential is based on public health
need and evidence of their efficacy and safety. In selecting essential medicines for
children, one of the first difficulties encountered was the relative lack of evidence
about medicines used to treat children with “neglected” diseases such as leishmani-
asis. The first EMLc included about 200 medicines in about 450 dosage forms.
Many were marked as needing further review, or had age restrictions on use
because of lack of data. The meeting report also lists many medicines for which
further evidence is required to confidently assess the benefits and harms of their use
in children. Some of the questions might be answered by systematic reviews of
existing information, but others require more research and drug development. The
published report of the WHO Expert Committee (WHO 2008a) also includes a
listing of Research Priorities for Children’s Medicines developed by a group of
experts convened by the WHO in October 2007.
A second EMLc was adopted in March 2009, and included for the first time a
listing of essential medicines that can be used in neonates (WHO 2009b). A
temporary Subcommittee of the WHO Expert Committee on the Selection and
Use of Essential Medicines prepared these first two Essential Medicines Lists for
children. The subcommittee meetings were held from 9 to 12 July 2007 and 29
September to 3 October 2008. In its last meeting, the Subcommittee recommended
that for the foreseeable future, it is essential that the EMLc remain separate from the
WHO Model List of Essential Medicines in order to maintain a critical focus on

the needs of children. However, it was considered that a Paediatric Subcommittee
as such would not be necessary and that it would be feasible for Expert Committees
to update the EMLc if appropriate consideration is given to the constitution of
future Expert Committees. Wide paediatric expertise will be necessary in order to
meet the needs of children and the demands of United Nations Millennium Goals 4
and 6 to focus on paediatric priorities of Resolution WHA60.20.
The most up-to-date WHO Essential Medicines List for children is available
from the WHO Selection of essential medicines – web-site (http://www.who.int/
selection_medicines/list/en/) as are the Technical reports of the Expert Committee
meetings (WHO 2008a; WHO 2009b).
5 Developing Appropriate Paediatric Formulations

for the Different Environments
Many of the essential medicines do not exist in formulations for children, and many
of the existing dosage forms of medicines for children are associated with significant
problems. Practical experience from the children, their caregivers, and health care
professionals from all over the world is that the existing paediatric formulations are
not optimal when it comes to dosing, dispensing, and administering the medicines
to children. This problem of lack of age-appropriate paediatric formulations has
been widely recognized, including by the US and EU paediatric initiatives, which
include measures designed to try to alleviate the problem.
The problems of paediatric formulations are even more difficult in resource poor
settings, and especially in areas of the world where high temperature and humidity
combined with problems of transport make logistics and storage a real challenge.
These problems exist at the country level for logistics needed for medicines supply,
at the level of local health care delivery and for the end users, the children and their
caregivers.
High humidity, present often in combination with high temperature, is detrimen-
tal to the quality of medicines and may render them inactive quite rapidly. Access to
electricity is not given in areas where temperatures are highest, therefore facilities
for cold storage of medicines – common requirement for liquid formulations such
as anti-infective agents once reconstituted – may not be reliably available in all
health care facilities, and even less so in households. Bulky formulations – liquids
are much more bulky than solid dosage forms – pose significant logistical
challenges, require more warehouse space, pharmacy space and compel parents to
carry home a heavier load of medicines. The transport problems for the end users
become even more significant in case of multi-drug treatments, long distances and
lack of means of transportation.
Paediatric formulations are most often in a liquid form but at the time of
dispensing or before administration may have to be dissolved in water. Water
needed to reconstitute medicines has to be clean, and clean water cannot be

assumed to be readily available all over the world. If age-appropriate formulations
are only available in bulk, containers for repackaging have to be provided, as there
is no guarantee that containers the patients/caregivers can provided are suitable
(e.g. may not be clean). Preferably medicines should be provided in packages ready
for dispensing. If injectable medicines are provided in strengths and vials for adults,
and are stable only for a short time after reconstitution, a lot of wastage occurs as
one child can use them only – the rest is waste. Appropriate handling of waste may
add to the problems.
Successful administration of the right dose of a medicine to a young child is
challenging all over the world. Clear instructions on administering medicines for
children that can be given to parents/caregivers are helpful. However, illiteracy is
common in many areas of the world and good illustrations or drawn instructions
have not been developed for paediatric use. The need for non-verbal instructions
that can be given to the parents who bring children to hospitals is highlighted when
the parents are not the ones who administer the medicines, so that they have to
communicate instructions to another caregiver (grandparents, house help, mother in
law, school matron, school nurse, teacher, etc). Given that medicine administration
in children is often complicated and requires specific directions, mistakes may
occur when information is transferred to “third parties”.
6 Accounting for Sociocultural Differences
In a global world sociocultural differences still play a major role, also when it
comes to paediatric medicines. Colour, form and taste of a medicine may not only
affect the success of administration to children but also the assessment people make
on the strength and effect of medicines. The preferences and interpretations can
have a significant cultural variability. These differences have been noted and for
example taste preferences routinely influence development of paediatric medicines
for the developed world. When the cultural variability of the less developed world is
added to that, the issue becomes even more complicated. A large pill may be
interpreted as “stronger” than a small one, and a bitter tasting medicine more
powerful than a sweet one. “Western” medicines may be considered too “strong”
and with too many “side effects” and traditional (homeopathic or herbal) medicines
may be preferred, a phenomenon not unfamiliar in the “western” world either. Pill
burden is a pragmatic problem, in any culture. Multiple concomitant diseases
increase the pill burden irrespective of geography, but are more common in areas
of high disease burden.
Traditional beliefs, misconceptions, irrational use of medicines are not unfamil-
iar anywhere in the world, but their variability and effect may be more pronounced
in resource poor setting where education and other services are available only to a
limited extent. The global coverage of data on sociocultural differences is limited,
and we do not even know the real relevance of the existing information. While there
can be no doubt that sociocultural differences need to be considered in global

development of paediatric medicines, we do not yet really know how and to what
extent.
7 Paediatric Fixed-Dose Combinations
Combination therapy is necessary for successful treatment of acute infections and

for prohibiting resistance to emerge in many of the priority diseases. Fixed dose
combinations (FDCs) can reduce the pill burden of combination therapies and
improve adherence to treatment. FDCs made their breakthrough in HIV/AIDS
treatment of adults and are now considered essential in other diseases such as
malaria and TB.
The concept of a FDC is valid for children also. In children the common
difficulties in administration and the increased physical mass that has to be carried
and stored when liquid formulations are used for long-term combination therapy are
additional arguments for use of FDCs. However, developing FDCs for children
brings some additional challenges. Developmental disposition of each individual
component (active ingredient) of a combination therapy may be different. The ratio
of the components providing optimal exposure for efficacy and safety may be
different in children when compared to adults, and may change in relation to
development. Simple linear scaling down of adult FDCs to lower strength
paediatric formulations may not be appropriate and increase in children the risk
of treatment failures and development of resistance. The latter may have wide
reaching consequences affecting also adults. Scoring of adult FDCs into infinitely
small fragments to adjust dosing for use of children cannot be safely done, unless
the pharmaceutical specifications of the product guarantee that dose accuracy is
maintained.
In practice, dosing children with 1/4 or ½ adult FDCs tablet is often feasible as
long as the tablet is suitable for scoring. When developing paediatric FDCs for
children needing lower doses than this, it is highly recommended to ascertain
whether developmental pharmacokinetic differences require changes of the ratio
of the components. Failure to do so has led to rejection of applications for inclusion
of newly developed paediatric FDCs on the EMLc.
8 The New Paradigm for Global Paediatric Formulations
The majority of paediatric formulations are in some liquid form – provided as

syrups or solutions, or powders that have to be dissolved in water. Liquid FDCs
exist, but they are usually more difficult to develop than solid FDCs. Many of the
presumed benefits of liquid formulations are not valid. Studies indicate that both
parents and children – sometimes unrealistically – in fact prefer tablets to liquids.
The possible benefit of the potentially greater dose accuracy of liquid vs. solid
formulations is not always necessary, when the active substance has a broad
therapeutic range (e.g. common antimicrobials) or is lost when inaccurate measur-
ing devices (e.g. a tablespoon) are used. Liquids are expensive, less stable than solid
forms, difficult to ship and store. As indicated earlier, liquid formulations are
particularly problematic in many areas of the developing world.
In the current growing interest and need to develop new paediatric formulations
of old and new medicines to benefit from the incentives and fulfil the requirements
of the US and EU paediatric legislations, great global benefit could be achieved if
one of the development specifications would be appropriateness for global use. An
expert meeting was convened by the WHO in December 2008 to identify the dosage
forms of medicines most suitable for children with particular attention to conditions
prevailing in the developing countries, and to flag future research required in this
area (WHO 2008c). The most important proposal was a shift from the traditional
paradigm of liquid paediatric formulations to flexible solid dosage forms. Many
stakeholders have subsequently endorsed this recommendation.
Flexible solid oral dosage forms such as tablets that are oro‐dispersible and/or
that can be used for preparation of oral liquids (for example, suspension or solution)
could potentially be used in very young children (0–6 months) provided the product
can be dispersed in breast milk from the mother. This type of product is feasible to
manufacture in facilities that have conventional tableting facilities, but requires
excipients that ensure stability and palatability. Examples of existing dispersible
tablet products suggest that they can be more affordable than standard liquid dosage
forms. These dosage forms could be used for many of the medicines necessary to
treat the diseases that are the major causes of mortality and morbidity in under five-
year-olds (lower respiratory tract infection, malaria, diarrheal diseases).
Some medicines require precise dose measurement or titration. For such oral
medicines, the most suitable dosage form should be based on use of a solid platform
technology (multi particulate solid, including those that could be dispersed to form
a liquid dose), rather than oral liquids. This makes possible production of tailored
doses and strengths as well as preparation as a range of dosage forms such as tablets
or capsules. Examples of currently existing forms are mini‐tablets and spherical
granules (pellets). These dosage forms are feasible to manufacture and can be
produced from standard excipients including those that are pre‐mixed and suitable
for a range of actives, and they have potential flexibility for constructing appropri-
ate FDCs.
Some chemical substances are “difficult molecules”, with problems of perme-
ability and/or solubility (defined using BCS classes). Techniques for these difficult
molecules need to be developed/or evaluated, including manipulation (e.g. spray
drying, micronization) prior to use with some platform technology that may pro-
duce suitable dosage forms for children.
9 Simplified Dosage Regimens Needed: Without Compromising

Safety and Efficacy
In resource poor settings, the medicine may be prescribed and dispensed by a

community health worker. If administration is not possible by the parents at
home, e.g. injections for severe neonatal infections, and treatment as in-patient is
not an option, administration of every dose will require a visit by the health care
worker to the patient or vice versa. Only a simple, short course of a minimal number
of administrations is feasible under such circumstances. Simplicity in dosing and
administration is also necessary if the treatment is administered at home by a parent
or a caregiver, and particularly if the dosing is to be determined by them. Such
challenges are common and unavoidable in programmatic approaches to priority
diseases such as malaria.
To adjust for developmental and size differences, drug doses in children are
typically calculated according to body weight. However, weight-based dosing may
be challenging in less developed countries where priority diseases such as malaria
are endemic because functioning weighing scales are scarce, and access to formal
health services is limited. The methods used to establish regional age-based
dose regimens for the treatment of uncomplicated falciparum malaria have
been based on “epidemiological” modelling, carried out to translate weight-based
recommendations to age-based dosing regimens for programmatic use in the target
population (Taylor et al. 2006). The basic assumption is that the recommended
mg/kg starting dose is correct, based on efficacy and safety data and PK data from
paediatric populations. This weight-based information is then converted to age-
bands, using regional weight-for-age reference curves from compiled country-
level, population-representative nutritional data.
For malaria and other diseases where medicines are bought over-the-counter,
age-based dosing is appropriate. For treatment and management of diseases such as
HIV, weight information is imperative, since ARVs have a narrow therapeutic
index, and weight change is used to monitor response to treatment.
Age-based dosing requires a drug with a relatively large therapeutic index,
because it considerably increases the variability in dose intake, which will lead to
some under- or over-dosing, particularly in drugs with relatively narrow therapeutic
indexes. In principle, medicines with a wide therapeutic index could be safely dosed
by age. Those with a narrow therapeutic index would need to be dosed by weight.
The determining factors for the accuracy and applicability of age-based dosing
include the availability of appropriate tablet that is preferably scorable, and solid
knowledge of the therapeutic dose range and therapeutic index (WHO 2009a). The
starting point, as with any dosing regimen, is appropriate efficacy, safety, and PK
data in the relevant age group.
The lack of data on the optimum target dose and therapeutic dose range for
paediatric medicines and the unavailability of appropriate paediatric dosage forms
result in children frequently being prescribed medicine doses that are inappropriate.
Sub-optimal dosing is a major determinant of treatment failure in individual
patients and may drive the development of drug resistance in the population.
Overdosing may lead to serious adverse effects in individuals and may negatively
affect the reputation of an efficacious medicine in communities, thereby affecting
use and compliance.
Population pharmacokinetic modelling (POPPK) and simulations have been
undertaken to evaluate some of the recommended ARV and TB treatment regimens
(WHO 2009a). The advantages of using POPPK modelling is that a broad spectrum
of subjects can be included, and covariates for size, age, genotype, binding proteins,
diet, and interacting drugs are incorporated into the model. For many important
medicines in use today, paediatric-specific PK data from large, well-conducted
clinical trials spanning the continuum of the paediatric age spectrum do not
generally exist. Paediatric PK data may be available from only a few published
studies, with small subject cohorts that restrict the ability to accurately determine
the true variability associated with specific PK parameters for each of the drugs.
However, modelling and simulation based on limited PK data in children can be
supplemented to a certain extent with information from adult studies and provide
valuable information, which ideally should be validated by exposure data collected
from subjects of different age ranges. The information from the modelling exercises
can also be used to design future studies of these drugs to better eliminate the
knowledge gaps.
10 Paediatric Clinical Trials in the Developing World
Many essential medicines have not been properly tested in children for efficacy and
safety. Without adequate clinical trials, regulatory authorities cannot approve use of
medicines in children. Approval of paediatric medicines by regulatory authorities,
even the stringent ones, in earlier times were often based on efficacy and safety
data-sets, which would be today considered insufficient. Clinical experience from
years of use may strongly indicate that there are no major paediatric safety concerns
with the dosage used. However, paediatric dosages tend to be biased towards
underdosing as a consequence of conscious or unconscious fear of dose related
toxicity and lack of appropriate PK and dose-ranging studies. These problems
affecting paediatric drug therapy, well illustrated by the TB medicines, are global
and call for additional clinical trials of many medicines having already approval for
use in children.
The need for paediatric clinical trials is global. The general ethical and scientific
principles for clinical trials are the same all over the world, and are discussed in
Section “The Concept of Essential Medicines”. However, differences between high
and lower income countries lead to problems and challenges, which require some
comments.
10.1 Ethical Aspects of Clinical Trials in the developing world
Clinical trials must be done in the developing world for diseases that do not exist
elsewhere, and to account for variables, which may affect dosing, safety, or efficacy.
These variables include differences in genetic and environmental factors, and
health-care provision. Such trials are necessary and provide a direct benefit for the
paediatric population from which the trial subjects come. It would be unethical not
do the trials, and treat the children without proper knowledge or not treat them at all.
Less developed countries have some characteristics, which make them increas-
ingly attractive for clinical trials not, or at least not primarily, intended to benefit the
local paediatric population. These characteristics include high prevalence of
diseases, commonly in treatment-naı̈ve form, and lower trial costs. Such trials
are usually intended to provide data for regulatory approval of a medicine in the
developed countries, and in the case of paediatric medicines especially in the areas
providing lucrative incentives for development of medicines for children. These
trials are not necessarily inherently unethical, but run the risk of leading to
exploitation, if the paediatric population from which the trial subjects come will
not have access to the medicine once it is approved.
For an individual child participating in a clinical trial in a developing country, the
ethical framework for recruitment and protection of the study subjects is provided
by international agreements (Chapter Ethical Considerations in Conducting Pediat-
ric Research). However, also at the individual level the real situation in a resource-
poor country may often be significantly different from that of a high-income country
child. In the environment the child is living, participation in a clinical trial may be
the only real chance to get a treatment that may be life saving, a maximum benefit on
individual level. In relation to this, the risk–benefit ratio would be positive even
when the risks could be long-term adverse effects not treatable in the local health-
care system or risk of relapse when the child has no longer access to the study
treatment after the trial ends. Children in resource-poor settings have an increased
risk of being exploited. In poor settings almost any form of reimbursement of
expenses may run the risk of being an undue inducement for the family to provide
consent for the participation of the child. Problematic may also be, if the study offers
a big benefit for the local community in the form of an improvement in health-care
infrastructure (facility, equipment etc.) that will remain after the study, but the risks
are borne by the child. However, a clinical trial may also bring risks to the local
community and health-care provision, if it focuses too much of the local resources
and captures the best health-care workers for a single disease, and leads to deterio-
ration of care for other health needs.
Principally the ethical framework of the international agreements makes provi-
sion to take care of these special challenges of the resource poor settings by the
local ethical committees and/or national authorities. In practice, it is not uncommon
that even when a system of ethical assessment and approval is in place paediatric
expertise may be lacking, or at least expertise on paediatric clinical trials of
medicines. A somewhat functional system of ethical assessment lacking appropri-
ate paediatric trials expertise, but recognizing vulnerability and rights of children,
tends not to approve applications for paediatric trials, often by not at all or belatedly
responding to the applications. While this may protect the children from exploita-
tion, it also denies them the opportunity to have better treatments through research.
10.2 Scientific Aspects of Paediatric Clinical Trials

in Developing World
The scientific criteria for planning and performance of a valid paediatric clinical
trial are similar all over the world. In the developing world, it may be easier to
recruit enough patients to find a significant difference, and to find treatment-naı̈ve
patients. On the other hand, normal values or validated scales used to measure end-
points may not be available for the population to be studied. Confounding variables
may be completely different or have a different scale. For example the capacity to
offer concomitant non-medical treatment for a psychiatric condition may not be
comparable to other settings and render the results difficult to generalize.
Practical problems in performing trials in developing world settings are numer-
ous, ranging from illiteracy of parents who should give consent, lack of electricity,
and problems of logistics to corruption and unforeseeable changes in regulations,
which may delay or make it impossible to export collected samples for the planned
analysis.
Within the scope of this book it is possible only to give some ideas about the wide
variety of ethical, scientific, and practical challenges of paediatric clinical trials in
developing world settings. It is clear that the international agreements and
conventions on ethics do not go to the level of interpretation needed to handle the
increasing redistribution of paediatric clinical trials to the developing world. Sup-
port to build competency and capacity for paediatric clinical trials is also needed. It
remains to be hoped that the WHO within the tasks set by the WHA 60.20 resolution,
and the main profiteers of the trial redistribution, the US and EU, take initiative to fill
the gaps in the international ethical framework and provide other support needed.
11 Price, Quality, and Access
Even when appropriate formulations of medicines for the important priority

conditions have been developed, they are often in poor supply in low-income
countries. This is mainly due to high prices, and weak medicines procurement
and supply capacity. Paediatric formulations are often more expensive than
formulations for adults. More generally, manufacturers are reluctant to undertake
research and development into medicines for children, due to the unpredictable and
smaller market size for these products.
Baseline data from a sample of African countries highlight discrepancies
between WHO’s first Model List of Essential Medicines for Children and national
lists and treatment guidelines. Drug regulatory review of medicine for children in
these countries is also highly variable.
After new medicines for children have been developed and appropriate
formulations and data on dosing, safety, and efficacy have become available, the
question comes up how to improve access to these new and better medicines at
country level.
11.1 Providing Access to Essential Medicines for Children

at Country Level
Any discussion on access to medicines for children has to start with the question:
access to which medicines? In practice, this implies that every national essential
medicines programme must first agree on the clinical guidelines for children, and
draw up a list of essential medicines for children. The most sustainable solution is
that the clinical guidelines for children be included in the national clinical
guidelines used for training and supervision, and that the list of essential medicines
for children be included in the national list of essential medicines for supply and
reimbursement (Fig. 1). When the national list of essential medicines for children
has been defined, focused efforts can start to increase funding for these medicines
through government supply, bilateral support, donations, Global Fund grants,
World Bank loans, etc.
This explains also why the selection of essential medicines for children was also
the first and most important step to guide future drug development. In 2006, an
analysis of the then current WHO Model List of Essential Medicines showed that
over hundred medicines listed by WHO did not include a formulation for children,
Clinical guidelines and a list of essential medicines

lead to better prevention and care
List of common diseases and complaints
Treatment choice
Training and Financing and

Supervision Supply of drugs
Prevention
and care
Fig. 1 Link between selection of essential medicines, clinical guidelines and the supply system
either because they were simply forgotten, or because they did not exist in the
market. The resulting list of “missing essential medicines for children” added a new
dimension to WHO’s concept of essential medicines.
When new children’s formulations have become available and added to WHO’s
global Model List of Essential Medicines, it is equally important that national
clinicians include the new medicine in their updated national clinical guidelines;
and that the national formulary committee includes the new medicine in their new
national list. In this regard it may help to prepare and present short clinical update-
sheets to make clinicians and formulary committee members aware of the new
evidence.
11.2 Quality: A Major Challenge
With regard to quality, there is always a tendency to buy the cheapest medicines
irrespective of quality. This is a dangerous approach, which needs to be resisted.
The product with the lowest price can only be chosen when at least minimum
quality standards are guaranteed. Within the UN system (but also used by the
Global Fund, World Bank, UNITAID and international NGOs), WHO operates a
programme of “prequalification” of suppliers and products for the treatment of
HIV/AIDS, tuberculosis, malaria (including the paediatric formulations for these
diseases) and a few other essential medicines for children (e.g. zinc tablets). This
system is based on rigorous international assessments of the product dossiers and
manufacturing site inspections (www.who.int/medicines; look under “prequali-
fication”). By the end of 2009, 239 products had been prequalified for UN procure-
ment, of which 34 are children’s formulations.
This prequalification programme is of great practical relevance for all national
and international procurement agencies, as it gives clear guidance in which
paediatric products available in international commerce have been approved for
UN procurement. This also removes the need for each and every national regulatory
agency to invest heavily in their own dossier assessments and expensive site
inspections in countries such as India, where most of the cheapest generic
medicines are produced. But the programme also has a special function in
paediatric drug development, by offering a mechanisms by which the quality of
newly developed medicines can be assessed and endorsed at the global level,
facilitating their regulatory uptake and procurement in developing countries.
11.3 Medicines Have to Be Affordable
Prices of children’s medicines are often significantly higher than the cost of adult
dosages making procurement and supply a challenge. There are many ways
to improve affordability of essential medicines, including those for children.
In general, the preferred mechanism is competition. Competition is best guaranteed

by the availability of several similar products of assured quality, and price trans-
parency. Globally, whole-sale prices for generic medicines from not-for-profit
suppliers are published by WHO and Management Sciences for Health (www.
msh.org). In addition, national price surveys can be performed, price negotiations
can be started, and pricing policies can be developed, including generic policies. In
case of high prices linked to patent protection and failure of price negotiations,
voluntary or compulsory licenses can be issued for local production or importation
of generic products. Parallel import (import of a registered branded product from
another country in which its market price is lower) is not generally recommended as
it undermines differential pricing agreements and leads, in the long run, to higher
prices for the poorer countries.
12 Rational Use of Medicines
About half of the medicines used are not prescribed in the most cost-effective
manner: overprescription, unnecessary prescription, wrong doses, overuse of
antibiotics, overuse of injections and prescriptions not in line with clinical
guidelines are very common. After that, about half the patients do not adhere to
the treatment; many never collect the medicines of the prescription; do not follow
the instructions or interrupt the treatment before it is completed. All this leads to
enormous medical and economic waste. The situation is not any better in the
treatment of children.
There are many proven effective ways to promote rational and cost-effective
prescribing (WHO 2002), such as the use of clinical guidelines and essential
medicines lists, drugs and therapeutic committees in districts and major hospitals,
and problem-based undergraduate training in pharmacotherapy. In general a com-
bination of interventions is more effective than isolated measures. In the case of
treatment of children, the use of clinical guidelines and standard protocols for use
by doctors and other health workers is the best option; especially for the treatment
and follow-up in rural clinics. This is also the way to promote the introduction and
use of newly developed essential medicines for children.
13 National Medicine Policy
Different aims and objectives of a national pharmaceutical programme are often

contradictory. For example, reimbursement restrictions may lead to irrational
alternative prescribing, and support to the national pharmaceutical industry usually
results in higher domestic medicine prices. A national medicines policy, when
developed in a consultative way, helps to bring out and resolve such diverging
interests (WHO 2001). The policy then becomes the expression of government
commitment to a common goal and a framework for action. For example, the 1996
national medicine policy of South Africa (Ministry of Health 1996) strongly
focuses on equity. By the turn of the century, 109 developing countries had
developed a national medicines policy.
With regard to children, in many developing countries the needs are so great
that drastic nation-wide measures are needed. In addition, several aspects of the
problem touch upon other departments, such as the medicine regulatory agency
(for speedy registration of medicines, quality assurance, licensing of national
production), supply and distribution (for inclusion of medicines for children in
the regular medicine supply system) and human resources (for clinical guidelines
and prescriber training programmes); or other ministries, such as the Ministry of
Finance (for additional funding for essential medicines for children, tax reductions,
inclusion of paediatric formulations in health insurance and reimbursement
schemes), the Ministry of Trade (for international trade agreements, patent legisla-
tion, compulsory licenses) and the Ministry of Education (for undergraduate and in-
service training).
14 Public Health Approach to Innovation
WHO gives public health-based guidance to innovation in many ways (Table 2).
First, the list of “missing essential medicines for children” describes exactly which
medicines or formulations are missing. This can help interested companies to
choose a certain niche in the market for drug development. Secondly, the published
criteria for the Model List of Essential Medicines describe exactly which clinical
and safety data will be needed for considering the new medicine for inclusion on
Table 2 Useful resources available from WHO

The WHO model list of essential medicines
The WHO Model List of Essential Medicines is a model for national programmes and
reimbursement decisions. It has been updated every 2 years since 1977. The Model List of
2009 (WHO 2009b) contains about 350 active ingredients and is divided into a main list and a
complementary list. Drugs are specified by international non-proprietary name (INN) or
generic name without reference to brand names or specific manufacturers. The List aims to
identify cost-effective medicines for priority conditions, linked to evidence-based clinical
guidelines and with special emphasis on public health aspects and considerations of value of
money
The WHO model formulary for children
The WHO Model Formulary (WHO 2008b) presents model formulary information on all
medicines on the Model List and is a useful reference to individual prescribers. It is also
intended as a starting point for developing national or institutional formularies. A separate
WHO Model Formulary for Children is available (WHO 2010)
The WHO medicines web Site: www.who.int/medicines
All WHO publications on essential medicines, including the Model List, Model Formulary,
Essential Medicines Library, guidelines for national drug policies, information on prices,
quality, prequalification, patent status, regulatory status are freely available on this website
WHO’s Model List of Essential Medicines. This helps companies in designing the
necessary studies and also further strengthens the public health approach to
innovation. These clinical and safety data, which are public, can later also
assist decision-making by national formulary committees. Thirdly, the WHO/UN
prequalification programme describes exactly the quality requirements for the
product application file, again guiding the innovation process and subsequent
national regulatory review.
The advantages for the manufacturers are not only that the clinical, safety, and
quality requirements of the missing paediatric formulations are clearly described
and that the assessment process is predictable. In addition, if the product is indeed
prequalified by WHO, most international and national medicine procurement
agencies are likely to procure the new product, and an increasing number of
national regulatory agencies will fast-track regulatory approval for their private
markets. The advantages for public health authorities are that separate in-depth
regulatory assessments are no longer needed, and that a fair competition is pro-
moted between “prequalified” products of assured quality, leading to lower prices.
References
Grimshaw JM, Russell IT (1993) Effect of clinical guidelines on medical practice: a systematic
review of rigorous evaluations. Lancet 342:1317–1322
Kafuko J, Bagenda D (1994) Impact of national standard treatment guidelines on rational drug use
in Uganda health facilities. UNICEF/Uganda, Kampala
Laing R, Hogerzeil H et al (2001) Ten recommendations to improve use of medicines in develop-
ing countries. Health Policy Plan 16:13–20
Ministry of Health (1996) National drug policy of South Africa. Pretoria
Robertson J, Forte G et al (2009) What essential medicines for children are on the shelf? Bull
World Health Organ 87:231–237
Taylor WR, Terlouw DJ et al (2006) Use of weight-for-age-data to optimize tablet strength and
dosing regimens for a new fixed-dose artesunate-amodiaquine combination for treating
falciparum malaria. Bull World Health Organ 84:956–964
WHO (2001) How to establish and implement a national drug policy. WHO, Geneva
WHO (2002) Promoting rational use of medicines: core components. WHO Policy Perspectives on
Medicines, Geneva
WHO (2003) The selection and use of essential medicines. Report of the WHO Expert Committee,
2002 (including the 12th model list of essential medicines). Technical Report Series, No 914.
WHO, Geneva
WHO (2008a) The selection and use of essential medicines. Report of the WHO Expert Commit-
tee, October 2007 (including the model list of essential medicines for children). Technical
Report Series, No 950. WHO, Geneva
WHO (2008b) The WHO model formulary. WHO, Geneva
WHO (2008c) Report of the informal expert meeting on dosage forms of medicines for children.
Available form: http://www.who.int/selection_medicines/committees/expert/17/application/
paediatric/Dosage_form_reportDEC2008.pdf
WHO (2009a) Report of the technical consultation on the use of pharmacokinetic analyses for
paediatric medicine development. Available form: http://www.who.int/childmedicines/prog-
ress/Pharmacokinetic_June2009.pdf
WHO (2009b) The selection and use of essential medicines. Report of the WHO Expert Commit-
tee, March 2009 (including the 16th WHO model list of essential medicines and the 2nd model
list of essential medicines for children). Technical Report Series, No 958. WHO, Geneva
WHO (2010) WHO model formulary for children 2010. WHO, Geneva
Woolf SH, Grol R et al (1999) Clinical guidelines: potential benefits, limitations, and harms of
clinical guidelines. BMJ 318:527–530
World Health Assembly (2007) Resolution WHA60.20 Better medicines for children.
Index
A Age-based dosing, 363

a, 185, 186, 188, 192, 193 Age-matched normal range, 117
Absorption, Distribution, Metabolism, Agranulocytosis, 170, 173
and Excretion (ADME), 182 AHS See Anticonvulsant
Acceptability, 92, 93, 95, 97, 105 hypersensitivity syndrome
Acceptable Daily Intake (ADI), 102 Alcohol
Access to essential medicines, 356, 367–368 consumption, 35, 37
Access to medicines, 354, 355, 359, 365, 367 ALF See Acute liver failure
ACEI See Angiotensin converting enzyme Alfentanil, lidocaine, theophylline, 141
inhibitors Allocation, 190, 191, 197
Acute liver failure (ALF), 171–174 Allometric scaling, 68–69
Adaptation American Academy of Pediatrics, 248
after birth, 18, 19 Aminoglycosides, 7, 10, 20
ADHD See Attention-deficit/ Anabolic androgenic steroids, 38
hyperactivity disorder Analysis, 182, 183, 187–192, 194–199
Adhesive urinary bags, 206 of covariance, 187–190
Adjuvants, vaccination final, 192, 196
AS02, 322, 324 interim, 182, 192, 196–199
AS04 and CpG 7907, 324 results, interim, 199
described, 322 sequential, 191, 194, 195
MF59 and AS03, oil-in-water, 324 of variance, 191
new, 322, 323 Analytical methods, 78, 80, 81, 209, 212
ADME See Absorption, Distribution, Angiotensin converting enzyme
Metabolism, and Excretion inhibitors (ACEI), 287
Administration routes, 92–101 Angiotensin II antagonists, 287
Adolescent Research Animal model(s), 21, 22, 27, 39
(Definition of Child), 239–240 Anthracyclines
ADRs See Adverse drug reactions cardiotoxicity, 31–32
Adverse drug reactions (ADRs), 170, 173, Anthrax, 138–139
174, 179, 339–341, 343–348, 350 Anthropometric, 128
Adverse events following immunization Antibiotics, 138
(AEFI) Anticoagulants
drug reaction, 318 pharmacodynamics, 31
reactogenicity, 328 Anticonvulsant hypersensitivity
standardized case definitions, 329–330 syndrome (AHS), 174, 176–179
AEFI See Adverse events following Antihypertensive dose-ranging trials, 144
immunization Antineoplastic agents, 287

DOI 10.1007/978-3-642-20195-0. # Springer-Verlag Berlin Heidelberg 2011
374 Index
Apoptotic neurodegeneration, 310 non-inferiority trials, 232

Archimedes model, 138 placebo controls, 232–234
Assumptions, 187, 188, 197 randomized withdrawal trials, 234
Asthma, 154, 155, 161 Christmas tree, 195
controller medication, 32 Citric acid, 206
Attention-deficit/hyperactivity disorder Clinical equipoise, 224, 231–233
(ADHD), 171–173, 182, 183 Clinical guidelines, 355, 358, 367–370
medication, 29, 32, 38–39 Clinical trial, 339, 340, 344–349, 356, 364–366
Autoregulation simulation, 137–138, 144
cerebral, 8 CMV infection See Cytomegalovirus infection
Cocaine, 21, 34, 35, 287, 292
Code of Federal Regulations, 247, 248, 255
B Cognitive development, 296, 298, 300,
b, 185, 186, 190, 193, 194 306–307, 310
Barrier Cohn fractionation, 331
blood-brain barrier, 7, 18 Compensation, 229, 231, 233, 237
gastrointestinal mucosal barrier, 20 Component analysis, 224–225, 230
Benzyl alcohol, 102, 103 fallacy of the package deal, 224
Best Pharmaceuticals for Children Act Composite endpoint, 155, 160, 161
(BPCA), 252, 254–256, 258, 260 Condition, 135, 138, 141
Betamimetics, 11, 25 95% Confidence Intervals (CIs), 186, 187,
Bias, 81, 85, 151, 289–293, 297, 298, 301 192, 195
Binding Confounding effects, 288–293
high-affinity acid binding sites, 18 Congenital defects, 286
plasma protein binding capacity, 7 Consent, 208
Bioavailability, 19, 20 Cord blood, 212
Biobanking, 203–213 Corticosteroids, 17, 272, 279, 287
Biological matrix, 211 Coumarin, 287
Biologics Control Act in 1902, 247 Covariates, 128–130, 139, 144
Biomarkers, 130, 139, 144 Crossover design, 187, 189, 190
Consortium, 258 Cyclosporine
Blood, 204–209, 211–213 pharmacodynamics, 26
sampling methods, 205 CYP1A2, 57, 58, 60
Bottom up, 127, 130–137, 141–145 CYP3A, 59
Boundaries, 191–198 CYP2C9/CYP2C19, 57, 58, 61–62
BPCA See Best Pharmaceuticals CYP2D6, 57, 60–62, 66, 67
for Children Act activity score, 67
Breast feeding, 21 genotyping, 67
Breath test, 206–207 CYP2E1, 57, 62–64
Cystic fibrosis, 154–155
Cytochrome P450 (CYP) mono-oxygenase
C activity, 176
Carbamazepine, 177, 178 Cytomegalovirus (CMV) infection
Cardiac defects, 301 intrauterine
Catheters, 205 described, 279
Channels maternal oral administration,
developing brain, 19, 22 VACV, 279
regulation of ductal tone, 13 VACV, description, 280
transepithelial electrolyte transport, 14–15
Child assent, 220, 221, 227, 237–240
Child-Pugh, 141 D
Choice of control group, 232–234 DAMOCLES, 198, 199
active controlled trials, 235 Data mining process, 129
Index 375
Data Monitoring Committee (DMC), 198, DPI See Dry powder inhalers
199, 236 Dried blood spot (DBS), 82–83, 211
DBS See Dried blood spot Drugs, 170, 171, 173–179 See also
Decision study, 188, 190 Medicinesabsorption, 53–55, 65, 66
Deductive, 129, 130, 137 The Gastrointestinal Tract, 53–55, 70
DeMets, D.L., 192 skin, 53, 55
Depression(s), 21–22, 35–38 abuse, 34, 37
Designs addiction, 34
adaptive, 187–198 assays, 209–212
crossover, 187, 189, 190 clearance(s), 25
response-adaptive, 187–190, 197 disposition, 9, 19–21, 24, 37
sequential, 191–198 distribution, 56–57
Deterministic simulation, 127–129 body composition, 53
Development extracellular water, 53
brain, 19, 22, 23 drug-metabolizing enzymes, 21, 36
changes, 6–9, 13, 18–19, 24–25, 39 elimination, 9, 24
period(s), 6–39 enteral absorption, 19–20
pubertal, 33, 34, 36, 37 excretion, 64–65
window(s), 16–17, 22–23, 27–28, renal function, 64, 65
31–32, 37–39 serum creatinine, 64
Developmental exposure, 129, 138, 144
pharmacokinetics, 51–70 illicit drug use, 37
stage, 150, 153, 154 metabolism
Dexamethasone, 187 cytochromes P450 (CYP450), 57
Diabetes, 18, 28, 31, 34, 37 metabolizing enzymes, 55, 57–60, 62,
Diapers, 206, 207 66, 68–69
Diethylstilbestrol, 286, 287 rash with eosinophilia and systemic
Difference, 182, 184–189, 191, 192 symptoms (DRESS), 174
clinically important, 189 targets, 10–16, 21–23, 25–27, 29–31, 37
clinically relevant, 184, 187, 188 Dry powder inhalers (DPI), 101
relevant, 182, 184, 187, 188, 192 Ductus arteriosus
statistically significant, 187 ductal closure, 13, 14
Direct benefit, 221, 224–230, 233, 237, 238 ductal constriction, 14
Directive 2001/83/EC, 260 ductal tone, 13–14
Disease, 150–162 patent ductus arteriosus (PDA), 8
Disinfectants perinatal switch, 12
alcohols, 334 Dysmenorrhea
aldehydes, 334 therapy, 34
chemicals treatment, 334 Dysmorphisms, 296, 299–300
description, 334
heat, 334–335
iodine, 335 E
oxidizing agents, 335 EaSt, 195
phenolics, 334–335 Eating disorders, 36
physical treatment, 334 Effect
quaternary ammonium compound, 335 actual, 194–195
Diuretics carry-over, 189, 190
furosemide, 14–15 expected, 194–195
thiazide, 14–15 size, 190, 192–195, 197
DMC See Data Monitoring Committee Effervescent dosage forms, 95
Dosages, 182, 183, 189 Efficacy, 183, 187, 195, 196, 198
Dose assessment, 149–162
loading, 7, 9 Elective abortion, 291, 303
maintenance, 9 EMA See European Medicines Agency
376 Index
Emax-model, 130 Extrapolation, 150, 158, 159, 161, 222,

EMLc See Essential Medicines List for 223, 248, 253, 254, 264
children
Endpoints, 150–162
Epilepsy, 23, 29, 37 See also Seizures F
Equipoise, 184, 186 Face masks, 101
Errors Facial clefts, 301–302, 309
type I, 185, 192, 196 FDA See Food and Drug Administration
type II, 185, 186, 193, 198 FDAAA See Food and Drug Administration
Essential medicines, 355–359, 364, 366–371 Amendments Act
Essential Medicines List for children FDC See Fixed dose combinations
(EMLc), 358–359, 361 Fetal analgesia
Estimation, 183, 186, 187, 190, 192, 195 intraperitoneal administration, 277
Ethanol, 103 nociceptial reaction, 277
Ethical framework, 365, 366 noxious stimulus, 276
Ethics, 356, 364–366 procedures and benefits, 277
committee, 192 spinothalamic connection, 276–277
Etomidate–®Lipuro, 192 Fetal goiter
EudraCT, 266 cordiocentesis and direct blood
EU, Regulation (EC) No 726/2004, 260 sampling, 280
European legislation hypothyroidism, 280
European Commission, 251, 259–261, 267 Fetal heart arrhythmias
European Medicines Agency (EMA), 183, defined, tachycardia and bradycardia, 278
187, 258–260, 267–268 digoxin use, 278
European Parliament, 259, 261, 264, 266 management, tachycardia, 278
European Union (EU), 251, 259–263, 265, Fetal medicine and treatment
266, 268 analgesia, 276–277
Community research programs, 267 CMV infection, 279–280
Directive (2001/20/EC), 260, 264 diagnostics, 272
Directive 2001/83/EC, 260 drugs and pharmacokinetics, placenta
Directives, 259, 260, 264 transfer
European Commission, 251, 259–261, 267 concentration, 273
European Council of Ministers, 259, 261 diffusion, 272–273
European Medicines Agency, 259–260 direct administration, routes, 273, 274
European Parliament, 259, 261, 264, 266 human fetal liver microsomes, 273
Food and Drug Administration (FDA), transplacental route, 273
247–258, 260, 265, 266 goiter, 280
Japanese authorities, 265 heart arrhythmias, 278
languages, 259, 263 lung maturation, corticosteroids, 279
Member States, 259–262, 265, 267 stem cell therapy, 275–276
National Institutes transfusions, 274–275
of Health (NIH), 252, 267 transplacental steroid, 272
network of networks, 267 Fetal stem cell therapy
regulation, 251, 258–268 arguments, transplantation, 275
regulation (EC) No 726/2004, 260 bone marrow transplantation, 275
regulation (EC) No 1901/2006, 260 intrauterine and MSC transplantation, 276
Regulations and Directives, 259 in-utero transplantation, 275–276
World Health Organization Fetal transfusions
(WHO), 265, 266 cordocentesis, 274
Events description, 274
adverse, 188, 198 intravascular, 274
Excipients, 92, 93, 95, 97, 99, 101–105 platelets, 275
Exclusivity, 249, 250, 254, 260, 265 survival rates, 274–275
Extraction, 207, 209, 212, 213
Index 377
First in Human (FIH), 231, 235–236 Hydantoins, 287, 288

Pediatric Trials, 231 Hypertension, 8, 11, 28, 31, 38, 155, 160
Fixed dose combinations (FDC), 361, 362 Hypoglycemia, 9, 18, 30
Fleming, T.R., 192 Hypospadia, 301
Flexible solid oral dosage forms, 362 Hypothesis, 184–187, 193, 194, 196, 197
Folate, 308–309 alternative, 185, 193
Folic acid antagonists, 287 null, 185, 194, 196, 197
Food and Drug Act, 247, 249, 256 Hypoxic-ischemic events, 65
Food and Drug Administration (FDA), 170,
247–258, 265, 266
Food and Drug Administration I
Amendments Act (FDAAA), 256 ICH E11, 255, 259, 263
Food and Drug Administration Modernization Idiopathic liver failure, 172
Act (FDAMA), 249–251, 253, 255 Immune dysregulation, 28
Food Drug and Cosmetic Act, 247 Immune system, 8, 9, 18, 24, 26
Futility, 192, 195–198 Incentives and rewards
market exclusivity, 118
patent extension, 118
G Incontinence, 157, 158
Gastric emptying, 54 Individualization, 84, 86
Gauze/cotton ball method, 206 Inductive, 129, 130, 137
GCLP See Good Clinical Laboratory Practice Infants, 183, 196
Generalizability, 188, 190 premature, 183
Glomerular filtration rate (GFR), 134, 141 Infusion pumps, 99
Good Clinical Laboratory Injuries
Practice (GCLP), 209 accidents, 29–30, 35
Growth Innovation, 356, 370–371
pubertal growth spurt, 28, 33–34 In silico, 137, 144
retardation, 188, 296, 299–300, International collaboration
309, 310 confidentiality arrangements, 265
stunted linear growth, 38 Interventions, 184–186, 188, 189, 191,
G-study, 188, 190 192, 196
Guidance control, 185
American Academy of Pediatrics, 236 experimental, 185, 188
CIOMS, 227, 229, 233 Intestinal drug metabolizing enzymes, 55
declaration of Helsinki, 222, 233 Intestinal motility, 54
European Medicines Agency (EMA), 222 Inverse normal method, 197
Institute of Medicine, 225, 227–228 In vitro diagnostic tests, 174
International Conference on
Harmonisation (ICH), 222, 233
J
Jaundice
H kernicterus, 18
H0, 185 physiological, 18
Hair, 207–208, 212 Juvenile idiopathic arthritis (JIA), 158, 159
Harm, 188, 189, 198
Haybittle, J.L., 192 K
Head circumference, 299 Kaiser Permanente, 138
Heart failure, 161
Heel prick, 205
Human knockout(s), 14 L
Human milk, 20 See also Breast feeding Lan, K.K.G., 192
Human research subject protections, 255, 258 Leftover material, 208–209, 213
378 Index
Leftover samples, 213 human fetal safety data, 286, 288

Level of evidence randomized controlled trials, 288
exposure–response relationships, 114, teratogens, 286
120, 253 Matrix, 210–213
paediatric disclaimers, 114 Maturation, 133–134, 139
pharmacokinetics, efficacy and safety, 117 brain, 22, 27
proof of efficacy, 114 physiological, 6, 24–28
safety and efficacy, 117 pulmonary, 8
shift in paradigm, 114 sexual, 33, 37
Levetiracetam, 141 windows of maturation, 16–17, 22–23, 39
Levofloxacin, 138–139, 143 Measurements
Lidocaine, 192 repeated, 187–190
Lifestyle, 31, 123, 124, 137–138, 291–292, 340 Meconium, 207, 212
Liquid formulations, 93, 95 Medical Birth Registry, 302–305
Liquid (LC-MS)/Gas (GC-MS) Medical treatment
chromatography-mass spectrometry, 210 clinical research, 112–113, 116–117
Lithium, 21, 288 effective treatments, 112
Liver cirrhoses, 141, 142 evidence synthesis, 112
Long-term consequences, 16, 31, 33, 34, 37, 38 health care practice, 112
Long-term follow-up, 17 Medication errors
Long-term safety, 37, 39 iatrogenic, 99
monitoring, 117 Medicines, 354–371 See also Drugs
Lung function, 154, 155, 161 Mesenchymal stem cells (MSC), 276
Lymphocyte Toxicity Assay (LTA), 174, Meta-analysis
176–179 prospective, 187–189, 191
Lymphocyte Transformation Metabolism
Test (LTT), 174–179 first-pass metabolism, 20
hepatic, 9–10, 20, 21, 29, 36
organs of metabolism, 9–10, 21, 25,
M 30, 36–37
Major congenital malformations, 296, 298, Metered-dose inhalers, 101
300–306, 308, 310 Metoclopramide, 196
Malignancies, 28, 29, 31, 34 See also Microassays, 209, 211, 212
Neoplastic diseases Microcephaly, 299–300
Market authorisation application, 122 Midazolam, 141, 142
Matching, 187, 189, 190 Migraine, 156, 159–160
Maternal pharmacotherapy, fetal risks Migration
confounding effects phthalates, 100
abortion data, bias, 291 Minimal/low risk, 225–226
bias, indication, 289 Mini-tablets, 95–97, 105
null hypothesis, 292–293 Minor anomalies, 296, 299–300
observational studies, 288 Minor increase over minimal risk, 225,
recall bias, 290–291 227–230, 234
retrospective ascertainment, 291–292 Misoprostol, 288, 291
retrospective studies, bias, 290 Modeling and simulation, 126–129, 144–146
sample size, 289 Monitoring, 77–86
time of enrollment, bias, 290 Monte Carlo simulation, 127, 129, 140
teratology principles Mortality, 188
congenital defects, 286 MSC See Mesenchymal stem cells
drug exposure timing and phases, 286 MTHFR gene, 309
drugs and chemicals, 286–288 Multiple drug assays, 212
Index 379
N Paediatric investigational plan (PIP), 119,

National Institutes of Health (NIH), 252, 253, 120, 122, 261–263
256–258, 266, 267 Paediatric strategy
National medicine policy, 355, 369–370 disease, 120
National Research Act, 248 dosing rationale, 120
Nebulizers, 101 drug delivery, 120
Neonates, 183 level of evidence, 120
Neoplastic diseases, 25, 29, 31 risk management, 121
See also Malignancies study implementation, 121
Neural tube defects, 297, 301, 309 Paediatric studies, 149–162
Neuronal plasticity, 22 PAH See Pulmonary arterial hypertension
Neurotransmitter(s) Pain, 21, 23, 34, 153, 155–157, 160,
acetylcholine (ACh), 27 183, 192
gamma-aminobutyric acid (GABA), 19, 22 Parachute, 184
Newborns, 184 Paradoxical effects, 25
Nicotine Paradoxical failure, 14
abuse, 34–35 Parental permission, 220, 221, 227, 237–240
autonomic nervous system, 27 Patent, 249, 250, 252–254, 256, 260,
fetal growth restriction, 34–35 262–265, 267
sudden infant death syndrome Patent ductus arteriosus (PDA), 8, 13, 65
(SIDS), 27, 34–35 PBPK See Physiologically based
NIH See National Institutes of Health pharmacokinetic
NONMEM program, 183 PD See Pharmacodynamics
The null hypothesis, 185, 194, 196, 197, 232, PDA See Patent ductus arteriosus
292–293 PDB See Prospect of Direct Benefit
Numerical, 127, 130, 137 PDCO See Paediatric Committee
PDE See Permitted Daily Exposure;
Phosphodiesterase
O Pediatric, 169–179
Obesity, 154 investigation plan (PIP)
O’Brien, P.C., 192 EudraCT, 327
Obstructive airway disease pharmacogenomics, 66, 67
mediators, 26 regulation, 260–262, 266, 267
Of delayed-type drug hypersensitivity, 174 Research Equity Act (PREA), 252–256
Off-label, 339–345, 349 rule, 248, 250–252
Off-patent, 252, 253, 256, 262–264, 267 Pemoline, 171–174
One-sided, 185, 187–189, 194–196 Performance, 154–157, 162
Ontogeny capacity, 154–157
ontogenesis, 11, 37 Permitted Daily Exposure (PDE), 104
ontogenetic changes, 20, 21 Personalised medicine
Opioids, 18, 21–22 phenotypes, 123
Optimisation, 78, 81 rare diseases, 123
Oral lyophilisates, 96–97 PEST, 195
Orphan Drug Act, 247, 249 Pharmacodynamics (PD), 10, 26, 31, 37,
Orphan Drugs, 339, 340, 342–344 78, 79, 82, 86, 127, 128, 130, 139
Outcome measures, 153, 157, 162 Pharmacokinetics (PK), 9, 27, 37, 78, 79,
Outcomes 82, 84–86, 127, 128, 130–146,
composite, 188, 189 182–184, 204–205, 208, 212
surrogate, 187–189 Pharmacometrics, 144
Pharmacotherapy, 127–128, 130, 137, 146
Pharmacotyping, 14
P Pharmacovigilance, 342–349
Paediatric Committee (PDCO), 261–264, 267 Phase, 184–198
Paediatric formulations, 356, 359–362, Phase I Enzymes, 59–64
366, 368, 370, 371 Phenylisohydantoin, 171
380 Index
Phosphodiesterase (PDE) vaccination

inhibitors, 12, 13 AEFI, 318
Physiologically based pharmacokinetic clinical vaccine trials, 324–327
(PBPK), 130–137, 141–143, 145 development, 320–321
Physiologically Based Pharmacokinetic historical overview, vaccines
Modeling, 131 development, 318–320
PK See Pharmacokinetics immunizations, 318
PK/PD, 130, 137, 139 licensure, 328
Pocock, S.J., 192 post-marketing settings, safety
Point estimates, 186, 187, 195 assessment, 328–330
PopED, 183 preclinical vaccine trials, 321–324
Population pharmacokinetic, 130, 131, 139 pre-licensure vaccine trials, 327–328
modelling (POPPK), 364 programs, immunization, 318, 320
pharmacodynamic, 130 Price(s), 356, 357, 366–371
Population PK, 204, 213 Product criterion, 197
Postmarketing period, 170 Programming
Power, 184–192, 194, 196 reprogramming, 28
Pregnancy Propofol, 192
teenager, 37 Proportions, 192, 193
Pregnancy registries, 298, 302–305, 308–310 Proposed Pediatric Study Request, 250
Premarketing studies, 170 Propylene glycol, 102, 103
Pre-/post-exposure passive immunization Prospect of Direct Benefit (PDB), 222–225,
antibody isotypes, 331 227, 229–236
applications, immunoglobulines, 332 Prostaglandin synthesis inhibitors
Cohn fractionation, 331 ibuprofen, 26
described, immunoglobulines/ indomethacin, 13
antibodies, 331 Prostanoid(s)
homologous and heterologous synthesis inhibitors, 13, 16, 26, 34
immunoglobulines, 332 Protein precipitation, 212
pre-existing allergy, 332–333 Psychomotor development, 306
products, dosage and administration Psychostimulants
route, 332 amphetamines, 32
sensitization and intravenous route, 333 methylphenidate, 32
virulence factors, immunoglobulin Puberty
donors, 331 delayed pubertal development, 34
Prequalification programme, 368, 371 precocious puberty, 33–34
Prescription drugs, 170 Public–private partnership, 115–117
Prescription Drug User’s Fee Act, 249 Pulmonary arterial hypertension (PAH), 155
Preventive medicines
disinfectants
Q
alcohols, 334
Questionnaires, 156, 157
aldehydes, 334
chemicals treatment, 334
description, 334 R
heat, 334–335 Radioactive isotopes, 206
iodine, 335 Randomization, 182, 184, 187–192, 194–196
oxidizing agents, 335 Rational Use of Medicines, 360, 369
phenolics, 334–335 RCTs, 184
physical treatment, 334 RDS See Respiratory distress syndrome
quaternary ammonium compound, 335 Reactive oxygen species (ROS), 309
prophylaxis Recall bias
avoidance, exposure, 331 malformation, 290–291
pre-/post-exposure passive prescription databases, 291
immunization, 331–333 prospective cohort, 291
Index 381
Receptors Salt-losing tubular disorders (SLT)

adrenergic receptors, 11, 25, 30, 32 DCT disorder, 14, 15
angiotensin receptor (ATR), 16 loop disorder, 14, 15
nicotinic acetylcholine receptors Sample
(nAChRs), 27, 38 collection, 80–82
opioid receptors, 21 path, 194, 195
prostanoid receptors, 11–13 preparation, 211–213
Recruitment, 188–190, 195, 196, 198 size estimation, 187
Rectal preparations, 98 size power, 184–186
Reflux sizes, 184–192, 194–198
gastroesophageal, 196 fixed, 194–197
Regression analysis, 191 Sampling, 204–209, 211–213
Regulations Scales, 156, 157, 160, 161
European Union, 221 Scientific necessity, 221–223, 227
United States (US), 228, 230, 236, Seizures, 18, 19, 22–25, 29 See also
238, 239 Epilepsyanticonvulsants, 23
Regulatory authorities long-term effects, 23
evidence from clinical trial, 113, 122 Selective serotonin reuptake inhibitors (SSRIs)
modern drug labelling system, 113 eating disorders, 36
product claims, 113 pulmonary hypertension, 8
Reimbursement, 121, 123, 124 Self assessment, 156
Renal excretory function, 21 Sepsis, 158
Renin-angiotensin system Sequential probability ratio test (SPRT),
filtration pressure (in the newborn), 15–16 193–195
Reproducibility, 187–189 truncated, 194
Resolution WHA60.20, 355, 356, 359, 366 Sexual behavior, 35
Respiratory distress syndrome (RDS), 8, 13 Shipping, 209, 213
described, 279 SI See Stimulation index
Respiratory syncytial virus, 187 Significance, 184–187, 189, 191, 192, 195
Restriction, 189, 190, 193 statistical, 185–187, 195
Results Simulation, 125–146
false-negative, 184–185 Skin permeability (permeability of skin), 7, 18
false-positive, 184–185 SLT See Salt-losing tubular disorders
inconclusive, 187 Sociocultural differences, 360, 361
randomized, 182, 187 Sotalol, 139–141
statistically significant, 187 SPRT See Sequential Probability Ratio Test
true-positive, 186 SSRIs See Selective serotonin reuptake
Retinoids, 288 inhibitors
Retinopathy of prematurity (ROP) Stable, 206, 213
mediators, 17 Standardisation, 159, 162
pathophysiology, 16–17 Standard operating procedures (SOP), 209, 213
Retrospective studies, 290, 307 Stimulation index (SI), 175–176
Review Stopping, 182, 186, 192, 194–199
systematic, 184, 197, 199 Storage, 207–209, 211, 213
Risk Management Plans, 266 Stratification, 187, 189, 190
ROP See Retinopathy of prematurity Study
ROS See Reactive oxygen species multicenter, 191
Study designs, 125–146
Subpart D, 248, 255
S Suicide, 34–36, 38
Safety, 204–205 Superiority, 185, 195
Saliva, 206 Supplementary Protection
Salivette, 206 Certificate (SPC), 260, 262, 265
382 Index
Suppositories, 97 U
Surrogate endpoints, 150–153, 155, 162 Uncertainty, 128, 129
Surrogate markers, 37, 39 United States Code, 246–247
Symptoms, 151, 153–156, 159–161 United States Congress, 247, 248
neurological, 188 Unlicensed, 340–345
drug, 341–344
Unmet medical needs, 115–118
T Urinary catheters, 205
Tablets Urine, 205–207, 211
dispersible, 95
enteric-coated, 95
orally disintegrating, 97 V
orodispersible, 96, 97, 104, 105 V(d) See Volume of distribution
splitting, 95, 96 Vaccination
sustained-release, 95 AEFI, 318
Taste clinical vaccine trials
electronic tongues, 104 endpoints, proof of efficacy, 326
taste-masking, 97, 104, 105 international databases, 325
taste perception, 104, 105 oral rotavirus vaccine, 327
Teratogenic risk, 287, 288, 290, 293, 296, 301 phase I, II and III, 325–326
Termination phase IV, 327
early, 198, 199 phases, post-marketing
Tests, 182, 184–189, 191–196 assessment, 324, 325
non-inferiority, 185, 188 pre-licensure vaccine, 324–325
one-sided, 185, 188, 194 developments
superiority, 195 academic/private research
triangular, 194–196 laboratories, 321
two-sided, 184, 185, 188, 189, 194 good laboratory practice, 321
Tetracyclines, 288 live-attenuated, 321
Thalidomide, 247, 288 prerequisites, 320–321
Theophylline, 141–143 immunizations, 318
apnea, 10 licensure, 328
therapeutic drug level post-marketing settings, safety assessment
monitoring (TDM), 10 alleged vaccine side effects, 330
Thin film strips, 96–97, 105 “The Brighton Collaboration”, 330
Top down, 127, 129–130, 137–141, 145 causality, 329
Transdermal products, 98 health professionals, 329
Transplant trials immunization programs, 329
renal, 188 nasal influenza vaccine, 329
Transporters, 55–57, 66–68, 70 public trust, 328
developing brain, 19, 22 reactogenicity, 328–329
protein P-gp, 20 risk-benefit, 328
the skin, 37, 38, 57 standardized case definitions, 329–330
transepithelial electrolyte transport, 14–15 preclinical vaccine trials
Trials, 182–199 adjuvants, 322–324
agricultural, 191 FDA and EMEA, 321
clinical, 184–198 non-toxicity proof, 321–322
N-of-1, 190 pharmacodynamic and
non-inferiority, 185 pharmacokinetic, 322
randomized, 188 product characteristics, 322
randomized clinical, 184, 191, 192 three-dimensional visualization, 321
superiority, 185 pre-licensure vaccine trials, 327–328
underpowered, 187–188, 191 EudraCT, PIP, 328
Triangular Test (TT), 194–196 EU Paediatric Regulation, 327–328
Tubular secretion, 134, 139 programs, immunization, 318, 320
Index 383
Valaciclovir (VACV) Vulnerability, 220, 222

description, 280 vulnerable, 220, 222
maternal oral administration, 279
Validation, 150–159, 161, 162
clinical endpoints, 117
Validity W
external, 189, 190 Weight-based dosing, 363
predictive, 188 WHO See World Health Organization
Valproic acid, 82, 83, 288, 289 WHO Essential Medicines List for children,
Value 358–359
neutral, 186 WHO model formulary for children, 370
Variances, 184–191 WHO Model List of Essential
Venepuncture, 205 Medicines, 355, 357, 359, 367, 370
Ventilation WINPOPT, 183
mechanical, 187 World Health Organization (WHO), 265, 266
Virtual world simulation, 127, 137–138 Written Request, 249–250, 255–257, 263,
Vitamin A, 288 265, 266
Volume of distribution (V(d)), 7, 9, 36, 56,
65, 69

Pediatric Clinical Pharmacology 2011

Uploaded by

Copyright:

Available Formats

Pediatric Clinical Pharmacology 2011

Uploaded by

Document Information

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Pediatric Clinical Pharmacology 2011

Uploaded by

Copyright:

Available Formats

Handbook of Experimental Pharmacology

For further volumes:

Prof. Dr. Matthias Schwab

Department of Clinical Pharmacology

ISSN 0171-2004 e-ISSN 1865-0325

# Springer-Verlag Berlin Heidelberg 2011

Printed on acid-free paper

Springer is part of Springer Science+Business Media (www.springer.com)

Historical development of pediatric pharmacology started at the very beginning of

Marburg, Germany Hannsjörg W. Seyberth

Part I General Considerations and Methodological Aspects

Basics and Dynamics of Neonatal and Pediatric Pharmacology . . . . . . . . . . . 3

Principles of Therapeutic Drug Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 77

Drug Delivery and Formulations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 91

Part II Development of Pediatric Medicines

Development of Paediatric Medicines: Concepts and Principles . . . . . . . . . 111

Study Design and Simulation Approach . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125

Efficacy Assessment in Paediatric Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 149

Safety Assessment in Pediatric Studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 169

Small Sample Approach, and Statistical

Sample Collection, Biobanking, and Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 203

Ethical Considerations in Conducting Pediatric Research . . . . . . . . . . . . . . . 219

Pediatric Regulatory Initiatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 245

Part III Specific Pediatric Pharmacology

Fetal Medicine and Treatment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 271

Fetal Risks of Maternal Pharmacotherapy: Identifying Signals . . . . . . . . . 285

Antiepileptic Treatment in Pregnant Women: Morphological

Preventive Medicines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 317

Postmarketing Surveillance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 339

Global Aspects of Drug Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 353

Maurice J. Ahsman Department of Clinical Pharmacy, Erasmus MC, Rotterdam,

Dina Battino Department of Neurophysiopathology and Epilepsy Centre, IRCCS

Jörg Breitkreutz Institut für Pharmazeutische Technologie und Biopharmazie,

Oscar Della Pasqua Division of Pharmacology, Amsterdam Center for Drug

Saskia N. de Wildt Intensive Care and Department of Pediatric Surgery, Erasmus

Abdelbasset Elzagallaai Division of Clinical Pharmacology and Toxicology,

Fatma Etwel Division of Clinical Pharmacology and Toxicology, Hospital for

Ulrich Heininger Universitäts-Kinderspital beider Basel (UKBB), Postfach, CH-

Steven Hirschfeld National Children’s Study Eunice Kennedy Shriver, National

Hans V. Hogerzeil Essential Medicines and Pharmaceutical Policies, World

Kalle Hoppu Poison Information Centre, Helsinki University Central Hospital

Evelyne Jacqz-Aigrain Department of Pediatric Pharmacology and

Ralph E. Kauffman Division of Clinical Pharmacology and Medical Toxicology,

Gregory L. Kearns Division of Pediatric Pharmacology and Medical Toxicology,

Gideon Koren The Motherisk Program, Division of Clinical Pharmacology and

Stephanie Läer Department of Clinical Pharmacy and Pharmacotherapy, Heinrich-

Pirjo Laitinen-Parkkonen Health Care and Social Services, City of Hyvinkää,

Ron A.A. Mathot Department of Clinical Pharmacy, Erasmus MC, Rotterdam,

Bernd Meibohm College of Pharmacy, University of Tennessee Health Science

Dirk Mentzer Paul-Ehrlich-Institut, Referate Arzneimittelsicherheit, Paul-Ehrlich-

Martin Offringa Department of Paediatric Clinical Epidemiology, Emma

Klaus Rose klausrose Consulting Pediatric Drug Development & More,

Agnes Saint-Raymond Scientific Advice, Paediatrics, and Orphan Drug Sector,

Matthias Schwab Dr. Margarete Fischer-Bosch-Institute of Clinical Pharma-

Hannsjörg W. Seyberth Klinik für Kinder- und Jugendmedizin, Philipps-Universität

Dick Tibboel Intensive Care and Department of Pediatric Surgery, Erasmus

Torbjörn Tomson Department of Clinical Neuroscience, Karolinska Institutet,

Johannes N. van den Anker Division of Pediatric Clinical Pharmacology,

Hanneke van der Lee Department of Paediatric Clinical Epidemiology, Emma

Vera Vlahović-Palčevski Department for Clinical Pharmacology, University of