Ch1 DrugOverview

In: Commonly Used Drugs ISBN: 978-1-63463-828-9
Editor: Rafik Karaman © 2015 Nova Science Publishers, Inc.
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Chapter 1
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Drug Overview
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Hatem Amin Hejaz1 and Rafik Karaman1,2
1
Pharmaceutical Sciences Department, Faculty of Pharmacy
Al-Quds University, Jerusalem, Palestine
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2
Department of Science, University of Basilicata, Potenza, Italy
Abstract
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A drug is a chemical substance with known biological effects on humans or
other animals. In the pharmacology field, a drug is defined as a chemical substance
used in the treatment, cure, prevention, or diagnosis of disease or used to otherwise
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enhance physical or mental well-being. Drugs usually affect either normal or
abnormal physiological processes. Drugs may be used for a limited duration, or on a
regular basis for chronic disorders. The way drugs are classified or grouped are
confusing. Therefore, a new approach of drugs classification is presented in this
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chapter along with general information on drugs which includes definition, drugs and
diseases types, drugs administration, drugs interactions and drug names. In addition,
the chapter describes some important aspects of drugs design and development, drug
effectiveness and safety, and drug errors.
Keywords: Drugs, Disease, Drug classification, Drug administration, OTC drugs,

Prescription drugs, Drug interactions, Drug safety
a
Abbreviations
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ADHD Attention Deficit Hyperactivity Disorder

ADME Absorption, Distribution, Metabolism and Excretion
AIDS Acquired Immune Deficiency Syndrome
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API Active Pharmaceutical Ingredients

BCS Biopharmaceutical Classification System
BP Blood Pressure
2 Hatem Amin Hejaz and Rafik Karaman
BTC Behind-the-Counter
CNS Central Nervous System
CoA Coenzyme A
COMT Catechol O-Methyltransfarase
Cox-1 Cyclooxygenase-1
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COX-2 Cyclooxygenase-2
DDT Dichlorodiphenyltrichloroethane
DMARDs Disease- Modifying Antirheumatic Drugs
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DNA Deoxyribonucleic Acid
DPP-IV Dipeptidyl Peptidase-IV
FDA Food and Drug Administration
GERD Gastroesophageal Reflux Disease
GIT Gastrointestinal Tract
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HCl Hydrochloric Acid
HMG-CoA 3-Hydroxy-3-Methylglutaryl-Coenzyme A
I.V Intravenous Injection
IM Intramuscular Injection
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INR International Normalized Ratio
IRB Institutional Research Board
Kcal Kilocalorie
LSD Lysergic Acid Diethylamide
MAO Monoamine Oxidases
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MAOIs Monoamino Oxidase Inhibitors
NSAIDs Nonsteroidal Anti-inflammatory Drugs
OMAs Organic Medicinal Agents
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OTC Over-the-Counter
POM Prescription Only Medicines
R&D Research and Development
RNA Deoxyribonucleic acid
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Rx Medical Prescriptions
SAM S-Adenosylmethionine
SAR Structure Activity Relationships
Sc Subcutaneous
SNRI Serotonin Nonselective Reuptake Inhibitor
SSRIs Selective Serotonin Reuptake Inhibitors
T3 Triiodothyronine
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T4 Thyroxine
TCA Tricyclic Antidepressant
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TNF Tumor Necrosis Factor
Drugs Definition
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A drug is a chemical substance that has known biological effects on humans or other
animals, used in the treatment, cure, mitigation, prevention, or diagnosis of disease or used to
Drug Overview 3
enhance physical or mental well-being. Drugs may be used for a limited duration, or on a
regular basis for chronic disorders. Drugs are generally taken to cure and/or relieve any
symptoms of an illness or medical condition, or may be used as prophylactic medicines. A
drug usually interacts with either normal or abnormal physiological process in a biological
system, and produces a desired and positive biological action. If the drug‘s effect helps the
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body, the drug is called a medicine, whereas, if its effect causes harm to the body, the drug is
classified as a poison [1-3]. The drugs can treat different types of diseases such as infectious
diseases, non-infectious diseases, and non-diseases (alleviation of pain, prevention of
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pregnancy and anesthesia).
Disease Classification
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There are three various ways of expressing human ill-health: disease, illness and sickness.
Disease is abnormal pathophysiological conditions affects either part or all or the body
organisms and associated with a group of signs, symptoms and laboratory findings linked by
a common pathophysiologic sequence.
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Disease may be caused due to external sources, such as infectious diseases such as
bacteria (pneumonia, salmonella), viruses (common cold, AIDS), fungi (thrush, athletes foot)
and parasites (malaria) or it may be caused due to internal dysfunctions, such as autoimmune
diseases or non-infectious diseases such as disorders of the human body caused by genetic
malfunction, environmental factors, stress, old age etc. (e.g., diabetes, heart disease, cancer,
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hemophilia, asthma, mental illness, stomach ulcers, arthritis). Diseases are most likely affect
people physically, and/or emotionally.
Diseases could be acute (short e.g., common cold, respiratory infections) or chronic (lasts
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for a long time, above six months e.g., diabetes, asthma, arthritis, cancer). Illness is a
condition of being unhealthy in the body or mind or it is the subjective state of the individual
who feels aware of not being well. The ill individual may or may not be suffering from
disease (illness can include lethargy, depression, anorexia, sleepiness, hyperalgesia and
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inability to concentrate). Sickness is the social role assumed by an individual suffering from
an illness.
Other terms for ill-health are syndrome and conditions; when the signs and symptoms
have not yet clearly been placed in a common pathophysiologic sequence the disease is
referred to as a syndrome. Diseases of a chronic nature are sometimes called conditions,
especially if they are present since birth [4-5]. Thus; a disease is a condition of impaired
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health resulting from a disturbance in the structure or function of the body.
Diseases may be classified into the following major categories:

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 Infectious diseases: also known as transmissible or communicable diseases. They are

caused by microorganisms, viruses, rickettsia, bacteria, fungi, protozoa and worms.
They are contagious illnesses that can be transmitted between people or animals in a
variety of ways. All communicable diseases are transmitted via some form of
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infectious pathogen. A communicable disease that passes through sexual contact is

called a sexually transmitted disease. Antibiotics, antivirals, antifungals,

antiprotozoal and anthelminthic agents are the drugs used to treat infectious diseases.
 Non-communicable diseases: non-infectious and non-transmissible. They are not
mainly caused by an acute infection and result in long-term health consequences and
often create a need for long-term treatment and care. They are chronic and
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considered as the number one cause of death and disability in the world. These
include chronic lung disease, autoimmune disease, heart disease, stroke, cancers,
asthma, diabetes, chronic kidney disease, osteoporosis, Alzheimer's disease, injuries
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and mental health disorders and more.
 Allergic diseases: are caused by antigens and foreign substances.
 Metabolic disorders: are caused by defects in the body's ability to carry out normal
reactions, these may be hereditary, deficiency, and congenital defects.
 Cancer: is a group of diseases involving abnormal cell growth with the potential to
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invade or spread to other parts of the body. The majority of cancers are due to
environmental factors and the remaining are due to inherited genetics.
 Toxic diseases: are caused by the consumption of substances, which are harmful to
the human body (caused by poisons).
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 Psychosomatic and mental diseases: psychosomatic disorders are diseases which
involve both mind (psyche) and body (soma). These may include affective emotional
instability, behavioral dysregulation, and/or cognitive dysfunction or impairment.
These include major depression, generalized anxiety disorder, schizophrenia, and
attention deficit hyperactivity disorder (ADHD). These diseases affected the ability
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of a person to work or study and harm his life including interpersonal relationships.
 Miscellaneous diseases: Among this class are foodborne illness or food poisoning,
airborne diseases, lifestyle diseases (any disease that appears to increase in frequency
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as countries become more industrialized and people live longer, especially if the risk
factors include behavioral choices like a sedentary lifestyle or a diet high in
unhealthful foods such as refined carbohydrates, trans fats, or alcoholic beverages)
and organic diseases (caused by a physical or physiological change to some tissue or
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organ of the body, excluding infections and mental disorders).
The general classification of diseases which is most widely used, is that based on
pathogenesis or disease mechanisms. Most diseases can be assigned in the following
classification:
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(i) Congenital diseases: also referred as birth defects; the conditions existing at birth and
often before birth, involve defects in or damage to a developing fetus. They may be
genetic (inherited or sporadic mutations, inheritance of abnormal genes from the
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parents) and non-genetic (environmental or accidental). The causes also include fetal
alcohol exposure, toxic substances (drugs and/or environmental toxin during
pregnancy), infections, lack of nutrients (folic acid), radiation and physical restraint
[5]. Congenital anomalies and preterm birth are important causes of childhood death,
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chronic illness, and disability in many countries.

Drug Overview 5
(ii) Acquired diseases: the medical condition which develops after birth. For example,
inflammatory, hemodynamic, growth disorders, injury and disordered repair,
disordered immunity, metabolic and degenerative disorders [5].
c.
Drugs Classification
There are different ways to group or classify drugs; therefore, different classification
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systems for therapeutic agents exist. A drug may be classified by its chemical structure; by
the way it is used to treat a particular condition, by its source or by its mechanism of action.
Each drug can be classified into one or more drug classes [3, 6].
Drug can be classified by the following ways:
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1. By its pharmacological effect; drugs are classified by their biological effect they
have, e.g., anti-inflammatory, analgesics, antiviral, anticancer, antianxiety, anti-
depressants, antipsychotics, antihypertensive, antibacterial agents, antiarrhythmic,
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diuretics and others [7-9].
2. By its chemical structure; drugs are grouped together by their chemical structures
based on a common skeleton they have. Some examples include sulfonamides,
sulfonylurea, tricyclic antidepressants, -lactams (penicillins), barbiturates, opiates,
steroids, catechol amines, aminoglycosides and others. All drugs of a certain
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chemical group have the same uses, or act on the same site of action [9].
3. By its target system; drugs in this class are classified according to a certain target or
target organ system in the body where they affect. Examples for such class include
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drugs acting on the cardiovascular system, ‎ drugs acting on the nervous system,
drugs acting on the gastrointestinal system and drugs acting on the musculoskeletal
system [9].
4. By its site of action; drugs are classified according to the drug targets (receptors,
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enzymes, cell lipids, pieces of DNA or RNA and carbohydrates) where they interact.
Most of drugs interact with enzymes or receptors to give their biological action and
others interact with other drug targets such as, drugs inhibit the enzyme
acetylcholinesterases. This classification is specific as most of drugs targets have
been identified. The drugs in this group have a common mechanism of action [9].
5. By its mechanism of action; there are a difference between actions of drugs and their
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effects. Drugs are classified by a specific biochemical interaction through which a

drug substance produces its pharmacological effect. Drugs are divided into six
classes according to their biochemical mechanism of action: (i) signal-transduction
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systems, (ii) other components of plasmatic membranes, (iii) intracellularly, (iv) a

gene therapy, (v) extracellularly and (vi) invasive agents [9-11]. A mechanism of
action usually includes the specific molecular targets to which the drug binds or
interacts. For example; the mechanism of action of non-steroidal anti-informatory
(NSAIDs) drugs is by inhibiting cyclooxygenase enzyme and thus stopping the
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production of prostaglandins and thromboxane and as a result reducing the pain and
inflammation. One major problem of pharmacology is that there is no such a drug
which produces only a single effect. The primary effect is the desired therapeutic
effect. Secondary effects are all other effects beside the desired effect which may be
either beneficial or harmful. Drugs are chosen to exploit differences between normal
metabolic processes and any abnormalities which may be present. Since the
differences may not be great, drugs may be nonspecific in action and alter normal
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functions as well as the undesirable ones which lead to unwanted side effects. The
mechanisms of action of some drugs are still unknown. Many drugs have multiple
mechanisms of action thus; it is sometimes difficult to agree on how to classify a
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particular drug.
6. By its physicochemical properties; this classification is also know the
biopharmaceutical classification system (BCS). It is the measures of permeability,
solubility and dissolution of the drugs. The system is designed mainly for oral drug
delivery as most of the drugs are administered orally. BCS is a tool in a drug product
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development used by the industry. The primary purpose of the BCS is to help in
qualifying drug products for a waiver of in vivo bioequivalence studies. The aim of
the BCS is the measurement of the permeability and solubility of the drug in vitro
and thus prediction of its performance in vivo. The information will help in the
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drug‘s formulation. The BCS places a given active pharmaceutical ingredients (API)
in one of four categories depending on its permeability and solubility [12]:
Class I: high permeability, high solubility; a drug substance is considered ―highly

soluble‖ when the highest dose strength is soluble in less than 250 ml water over a pH range
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of 1–7.5 and 37 °C. A drug substance is considered ―highly permeable‖ when the extent of
the absorption (parent drug plus metabolites) is more than 90% of the administered dose.
Those compounds are well absorbed and their absorption rate is usually higher than their
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excretion. Examples include metoprolol, amiloride, chloroquine, cyclophosphamide,
diazepam, digoxin, doxycycline, fluconazole and etc.
Class II: high Permeability, low Solubility; drug‘s absorption in this class is generally
slower than those in Class I. The dissolution-rate of these drugs is limited. However, specific
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techniques may be considered to enhance their dissolution rate. The bioavailability of those
products is limited. Examples for this class include glibenclamide, bicalutamide, ezetimibe,
carbamazepine, dapsone, ibuprofen, nifedipine, sulfamethoxazole, trimethoprim and etc.
Class III: Low Permeability, High Solubility; drugs in this class are quite soluble and
generally have rapid dissolution rates; however, their absorption is limited due to their low
permeation. The formulation method to be used should change the permeability or gastro-
intestinal duration time and thus enhance intestinal absorption. Examples include cimetidine,
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abacavir, acetaminophen, acyclovir, allopurinol, atenolol, captopril, codeine phosphate,

metformin, promethazine, sodium cloxacillin, ibuprofen and etc.
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Class IV: Low Permeability, Low Solubility; drugs in this class have significant problems
due to their low solubility and low permeability. Those compounds have a poor
bioavailability. Usually they are not well absorbed over the intestinal mucosa and a high
variability is expected. Techniques can be considered regarding selection of excipients
designed to enhance their dissolution rates and absorption. Examples include
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hydrochlorothiazide, furosemide, ritonavir, acetazolamide and etc.

Drug Overview 7
7. By its source or origin; drugs can be classified according to their origin:
(i) Natural compounds: materials obtained from either plant or animal, such as vitamins,
hormones, amino acids, antibiotics, alkaloids and glycoside. Natural products
(secondary metabolites) have been the most successful source of potential drug leads.
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(ii) Synthesis compounds: they are chemically produced in a laboratory, either pure
synthesis or synthesis of organic compounds whose structures are closely related to
those of naturally occurring compounds.
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(iii) Semi-synthesis compounds: some compounds either cannot be purely synthesized or
cannot be isolated from natural sources in low cost. Therefore, the natural
intermediate of such drugs could be used for the synthesis of the desired product such
as semisynthetic penicillins [13].
8. By its activity: drug activity can be classified as structurally non-specific drugs or
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structurally specific drugs. The actions of structurally non-specific drugs result from
accumulation of a drug in some vital part of a cell with lipid characteristics such as
general anesthetics, hypnotics, some bactericidal and insecticides. The structurally
non-specific drug depends on physical properties like solubility, partition coefficients
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and vapor pressure and not on the presence or absence of some chemical groups [14].
Structurally specific drug is dependent upon the interaction of the drug with a
cellular receptor. It is dependent upon factors such as the presence or absence of
certain functional groups, intramolecular distance, and shape of the molecules. The
drug activity is not easily correlated with any physical property and small changes in
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the structure often lead to changes in activity.
9. By its route of administration: route of administration is the path by which a drug or
other substance is taken into the body. Route of administration are generally
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classified by the location at which the drug is applied or where the target of action is.
Each route of administration has specific purposes, advantages, and disadvantages
[15-17]. Drugs are introduced into the body by several routes: (a)
Gastrointestinal/enteral: administration through the gastrointestinal tract (GIT) is
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termed enteral or enteric administration (meaning 'through the intestines'). Usually

includes oral and rectal administration. Sublingual (under the tongue) and buccal are
sometime classified as enteral. Enteral administration can be used for systemic
administration such as tablets and capsules, as well as local (topical), such as enema.
Many drugs can be administered orally as liquids, capsules, tablets, or chewable
tablets. The oral route is the most often used and most convenient because it is the
safest and least expensive. Some drugs are placed under the tongue (taken
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sublingually) or between the gums and teeth (buccal). Nitroglycerin (used to treat
angina) is given sublingually, has a rapid absorption and an immediate effect. Many
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drugs that are administered orally can also be administered rectally as a suppository.
A suppository is prescribed for people who cannot swallow (pediatrics, elderly).
Other routes of administration are used when the oral route cannot be used. For
example, when a person cannot take anything by mouth or a drug must be
administered rapidly or in a precise or very high dose, or a drug is poorly or
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erratically absorbed from the digestive tract. b) Central nervous system: this includes
epidural (injection or infusion into the epidural space), intracerebral (into the
cerebrum) direct injection into the brain (e.g., treatment of brain malignancies and
intracerebroventricular (into the cerebral ventricles) and (c) Other locations: this
includes; intravenous, intramuscular, intravaginal, intrauterine, epicutaneous or
topical (application to the skin). Topical: local effect, substance is applied directly
where its action is desired to a specific location. Examples, epicutaneous,
inhalational, enema, ophthalmic drugs/ eye drops (onto the conjunctiva), and otic
c.
drugs (ear drops). Enteral: administration involves any part of the GIT. The desired
effect is systemic; drug is given via the digestive tract. The drug may be introduced
orally by mouth or by gastric feeding tube, duodenal feeding tube, or gastrostomy.
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Parenteral: desired effect is systemic; substance is given by routes other than the
digestive tract. Examples: intravenous, intra-arterial, intra-muscular, intracerebral,
intracerebroventricular and subcutaneous (hypodermoclysis).
10. By its safety during pregnancy: many drugs are used in pregnancies. The most
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commonly used drugs include antiemetics, antacids, antihistamines, analgesics,
antimicrobials, diuretics, hypnotics, tranquilizers, and social and illicit drugs.
Medications taken by the pregnant woman can cross the placenta and enter the
developing baby's bloodstream. A medicine's effect on the unborn baby depends on
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the medication and the trimester in which the medicine is taken. Drugs that cross the
placenta may have a direct toxic effect or a teratogenic effect. The food and drug
administration (FDA) classifies drugs into 5 categories (A, B, C, D and X, Table 1)
based on the potential for producing birth defects or safety for use during pregnancy.
Drugs that fall into either class A or B are considered safe and are routinely used [18-
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19].
Category A: these drugs have been tested and found to be safe during pregnancy.
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Controlled studies in women fail to demonstrate a risk to the fetus in the first trimester
(and there is no evidence of a risk in later trimesters), and the possibility of fetal harm
appears remote. Category A includes drugs such as folic acid, vitamin B6, and some
thyroid medicines in prescribed doses.
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Category B: these drugs are frequently used during pregnancy and do not appear to cause
major birth defects or other problems. Animal-reproduction studies have not
demonstrated a fetal risk but there are no controlled studies in pregnant women, and
animal-reproduction studies have shown an adverse effect that was not confirmed in
controlled studies in women in the first trimester (and there is no evidence of a risk in
later trimesters). Category B includes some antibiotics, acetaminophen, aspartame,
famotidine, prednisone, insulin, and ibuprofen. Pregnant women should not take
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ibuprofen during the last three months of pregnancy.

Category C: no studies in animals have revealed adverse effects on the fetus (teratogenic
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or embryocidal or other) and there are no controlled studies in women, or studies in

women and animals are not available. It is wise to avoid taking the medications during
pregnancy. Drugs should be given only if the potential benefit justifies the potential risk
to the fetus. Always the pregnant woman should consult the doctor about taking any
medications, whether prescription or over-the-counter.
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Category D: there is a positive evidence of human fetal risk, but the benefits from use in
pregnant women may be acceptable despite the risk (e.g., if the drug is needed in a life-
Drug Overview 9
threatening situation or for a serious disease for which safer drugs cannot be used or are
ineffective).
Category X: studies in animals or humans have demonstrated fetal abnormalities, or there
is evidence of fetal risk based on human experience or both, and the risk of the use of the
drug in pregnant women clearly outweighs any possible benefit. The drug is
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contraindicated in women who are or may become pregnant.
Table 1. Classification of some drugs [19]
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Pharmaceutical agent Category Pharmaceutical agent Category
Acetaminophen/Paracetamol B Tetracycline D
Acetylsalicylic acid/Aspirin D Triamcinolone (skin) C
Amoxicillin B Chloramphenicol X
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Amoxicillin with clavulanic acid B Sulfonamide X
Cefotaxime B Misoprostol X
Diclofenac C Finasteride X
Isotretinoin X Methimazole X
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Leflunomide X Valproic Acid X
Loperamide B Metronidazole X
Paroxetine D Warfarine X
Phenytoin D Lithium X
Rifampicin C Alcohol X
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Thalidomide X Theophylline C
As mentioned previously, drugs can be classified according to various criteria including

chemical structure or pharmacological action or origin. Since there is uncertainty in the
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relationship between chemical structure and pharmacological activity, it would be unwisely to
classify all drugs on the basis of their chemical structures or origin. Therefore, it is
advantageous to classify them according to their medicinal use. Using this classification we
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may divide drugs into the following main groups [20]:
 Chemotherapeutic agents: those drugs which are used to fight pathogenic, used to
cure infectious diseases and cancer such as sulphonamides, antibiotics, antimalarial
agents, antivirals, anticancer agents and etc.
 Pharmacodynamic agents: drugs that act on the various physiological functions of the
body, used in non-infectious diseases such as cholinergic, adrenergic, hallucinogenic
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and sedatives.
 Miscellaneous agents: such as narcotic analgesics and local anesthetics.
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Drugs are classified into different groups according to their chemical characteristics,
structure and how they are used to treat specific disease. There are about eighty such broad
categories of drugs under therapeutic classification, they are: [7-8, 13, 21-24].
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Analgesics: agents that relieve pain without causing loss of consciousness. Examples
include acetaminophen, ibuprofen and aspirin.
Anesthetics: produce lack of feeling either local or general depending upon the type and
way of administration. Examples include lidocaine and procaine.
Antacids: neutralize acid such as magnesium hydroxide, aluminum hydroxide and
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calcium carbonate.
Anthelmintics: used to treat worm infections such as albendazole, mebendazole,
triclabendazole, levamisole, aminoacetonitrile, flubendazole and tiabendazole.
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Antianemics: prevent or cure anemia or increase the number of red blood cells or the
amount of hemoglobin in the blood, deficiencies of which characterize the disorder known as
anemia. Examples of this class are ferrous sulfate, folic acid and vitamin B12.
Antianginals: prevent or relieve angina attacks, used in the treatment of angina pectoris, a
symptom of ischemic heart disease. Examples include nitroglycerin, isosorbide dinitrate,
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isosorbide mononitrate), acebutolol, oxprenolol, verapamil, amlodipine, nifedipine and
Diltiazem.
Antianxiety agents: relieve anxiety and muscle tension such as chlordiazepoxide, valium,
alprazolam, clonazepam, oxazepam, clorazepate, rromazepam and afobazole.
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Antiarrhythmics: control cardiac arrhythmias such as lidocaine, propranolol, quinidine,
procainamide, phenytoin, atenolol, amiodarone and verapamil.
Antibiotics: destroy or inhibit growth of microorganisms; agents target the bacterial cell
wall e.g., penicillins and cephalosporins or cell membrane e.g., polymyxins, those targets
protein synthesis e.g., macrolides, lincosamides, tetracyclines, aminoglycosides, those
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interferes with essential bacterial enzymes e.g., rifamycins, lipiarmycins, quinolones, and
sulfonamides. Others antibiotics include cyclic lipopeptides (such as daptomycin),
glycylcyclines (such as tigycycline), oxazolidinones (such as linezolid) and lipiarmycins
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(such as fidaxomicin).
Anticholinergics: block parasympathetic nerve impulses; decrease oral and respiratory
secretions such as atropine, trihexyphenidyl, benzatropine, ipratropium bromide and
bupropion.
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Anticoagulants: prevent or delay blood clotting such as heparin, warfarin, dabigatran,

rivaroxaban and apixaban.
Anticonvulsants: prevent or relieve convulsions/seizures such as phenytoin,
ethosuximide, carbamazepine, valproic acid, eslicarbazepine acetate, pregabalin, vigabatrin,
felbamate and stiripentol.
Antidepressants: prevent or relieve symptoms of depression; tricyclic antidepressant such
as imipramine, monoamino oxidase inhibitors (MAOIs) such as phenelzine and
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isocarboxazid, and selective serotonin re-uptake inhibitors (SSRIs) such as fluoxetine and
fluvoxamine.
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Antidiabetics: used to manage diabetes.

Antidiarrheal agents: prevent or relieve diarrhea; inhibit peristalsis and reduce fecal
volume. Examples include methylcellulose, bismuth subsalicylate, electrolyte and bulking
agents such as fibers.
Antidotes: counteract poisons and their effects. Examples include naloxone: antidote of
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opioids, flumazenil: antidote of benzodiazepines, N-Acetyl cysteine: antidote of paracetamol,

deferoxamine: antidote of iron, ethanol or fomepizole: antidote of methanol and ethylene
glycol.
Drug Overview 11
Antidysrhythmics: control and prevent cardiac dysrhythmias

Antiemetics: prevent or relieve nausea and vomiting. Examples include
trimethobenzamide, dimenhydrinate, metoclopramide, promethazine and dronabinol.
Antiflatulents: relieve gas and bloating in GI tract. Examples include simethicone,
lactase, beano, marmite, epazote and asafetida.
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Antifungals: kill or inhibit growth of fungi. Examples include amphotericin B, candicidin,
natamycin, nystatin, econazole, ketoconazole, tioconazole, fluconazole, terbinafine, benzoic
acid, flucytosine and griseofulvin.
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Antigout agents: inhibit production of uric acid. Examples include colchicine,
allopurinol, benzbromarone, febuxostat, sulfinpyrazone and Probenecid.
Antihistamines: act to prevent the action of histamine (allergies). Examples include
fexofenadine, diphenhydramine, brompheniramine, cyproheptadine, loratadine and
bromodiphenhydramine.
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Antihyperlipidemic agents: used to lower abnormally high blood levels of fatty
substances (lipids). Examples include atorvastatin, gemfibrozil, lovastatin, niacin and
simvastatin.
Antihypertensive agents: prevent or control high blood pressure. Examples include
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clonidine, methyldopa, metoprolol, enalapril and nifedipine.
Anti-impotence agents: used to treat erectile dysfunction. Examples for such class include
sildenafil; Viagra, tadalafil; Cialis, vardenafil, prostaglandin E1, papaverine and phentolamine.
Anti-infective agents: kill and inhibit growth of bacteria.
Anti-inflammatory agents: prevent inflammation. Examples include ibuprofen, naproxen
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and aspirin.
Antimanic agents: used for treatment of manic episode of manic-depressive and bipolar
disorder. Examples for such class include lithium, haloperidol, clonazepam and lorazepam.
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Antimigraine agents: cause vasoconstriction in large intracranial arteries. Examples
include 2-bromo-lysergic acid, amidrine, cafergot, ergotamine, iprazochrome, lasmiditan,
methysergide, migraleve, oxetorone, telcagepant, treximet and antimigraine.
Antineoplastic agents: prevent the replication of neoplastic cells; used to treat tumors.
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Examples include busulfan and cyclophosphamide.

AntiParkinsonian agents: used for palliative relief of major symptoms of Parkinson
disease. Examples include L-dopa, ropinirole, amantadine, deprenyl and apomorphine.
Antiprotozoal agents: destroy protozoa. Examples include metronidazole, furazolidone,
eflornithine, melarsoprol, ornidazole, paromomycin, pentamidine, pyrimethamine and
tinidazole.
Antipsychotic agents: used to treat psychotic disorders. Examples include amisulpride,
a
aripiprazole, clozapine, olanzapine, quetiapine, risperidone, sertindole, chlorpromazine,

flupentixol, haloperidol, levomepromazine, pericyazine, perphenazine, pimozide, sulpiride,
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trifluoperazine and zuclopenthixol.

Antipyretics: reduce fever. Among the examples included in this class are paracetamol
and aspirin.
Antiretroviral agents: used to manage HIV infections. This class includes maraviroc,
enfuvirtide, zidovudine, abacavir, lamivudine, emtricitabine, ritonavir, elvitegravir and
N
nevirapine.
Antispasmodics: control hyper motility in IBS. Examples include anisotropine, atropine,

cindinium, hyoscyamine, dicycloverine, mebeverine, donnatal, metaxalone, methocarbamol,
chlorzoxazone, dantrolene and baclofen.
Antituberculosis agents: used in treatment of tuberculosis; inhibit growth of
mycobacteria. Among examples included in this class are isoniazid, ethambutol, rifabutin,
c.
rifapentine, pyrazinamide, rifampin, streptomycin, kanamycin, ciprofloxacin and thioridazine.
Antitumor necrosis factor agents: slow and halt the destruction of joints by disrupting the
activity of tumor necrosis factor (TNF). Examples include etanercept, infliximab,
In
adalimumab, golimumab and certolizumab pegol.
Antitussive agents: prevent or relieve cough. This class includes codeine,
dextromethorphan, guaifenesin and benzonatate.
Antiulcer agents: used in treatment of active duodenal ulcer and for pathological hyper
secretory; controls stomach acid. Examples include cimetidine, ranitidine, nizatidine and
rs
famotidine.
Antivirals: combat a specific viral disease such as herpes. Examples include acyclovir,
zanamivir, penciclovir, oseltamivir, Zidovudine and famciclovir.
Bone resorption inhibitors: treat and prevent osteoporosis. Examples include alendronate,
he
risedronate, ibandronate, zoledronic acid, raloxifene, denosumab and teriparatide.
Bronchodilators: dilate the bronchi. This class includes albuterol, isoproterenol,
salbutamol, salmeterol, formoterol, ipratropium, theophylline and tiotropium.
Cardiac glycosides: exert a positive inotropic effect on the heart; increase strength and
force of contractions and slow heart rate. Examples include digitalis preps; digoxin and
is
digitoxin.
Contraceptives: device, method or agent that prevents conception. Examples include
intrauterine device, progestogens and estrogens.
bl
Corticosteroids: suppress inflammation and modify normal immune response. This class
includes cortisol, prednisone, methylprednisolone, triamcinolone acetonide, fluocinonide,
betamethasone, dexamethasone and hydrocortisone 17-butyrate.
COX-2 Inhibitors: inhibit cyclooxygenase (COX-2) enzyme found in joints and other
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areas affected by inflammation. Examples include rofecoxib and celecoxib.

Decongestants: reduce nasal congestion and/or swelling; produce vasoconstriction.
Examples for such class are pseudoephedrine, phenylephrine, naphazoline and
xylometazoline.
Disease-modifying antirheumatic drugs (DMARDs): may influence the course of disease
progression of rheumatoid arthritis. Examples include leflunomide, penicillamine,
cyclophosphamide, methotrexate and auranofin.
a
Diuretics: increase the excretion of urine. Examples include loop diuretics such as
furosemide, thiazides diuretics such as hydrochlorothiazide, carbonic anhydrase inhibitors
ov
such as acetazolamide and methazolamide, potassium-sparing diuretics such as

spironolactone and amiloride, calcium-sparing diuretics such as thiazide (chlorothiazide and
hydrochlorothiazide), Osmotic diuretic such as mannitol and low ceiling diuretic such as
bendroflumethiazide and hydrochlorothiazide.
Electrolytes: treat or prevent electrolyte depletion. They are used to replace fluids and
N
minerals such as sodium and potassium lost due to diarrhea and vomiting. They help
preventing or treating the loss of too much body water (dehydration).
Drug Overview 13
Emetic agents: used to induce vomiting. Examples include apomorphine, ipecac syrup,
hydrogen peroxide and xylazine.
Expectorants: facilitate the removal of secretion from bronco-pulmonary mucous
membrane. Examples include guaifenesin, carbocysteine, potassium iodide and potassium
guaiacol sulfonate.
c.
Gastric acid-pump inhibitors: suppress gastric acid secretions; also used for
gastroesophageal reflux disease (GERD). Examples include pantoprazole, omeprazole,
lansoprazole and rabeprazole.
In
Hemostatic agents: control or stop bleeding. Examples for such class include vitamin K,
aminocaproic acid, chitosan, fibrinogen and aluminum sulfate.
Hormone replacement (HRT) agents: treat vasomotor symptoms of menopause.
Examples for such agents are Estrogen and progestin derivatives.
Hypnotics: produce sleep or hypnosis; depress CNS. Examples include chloral hydrate,
rs
ethchlorvynol, secobarbital, phenobarbital, methaqualone, alprazolam, lorazepam, diazepam,
clonazepam and zopiclone.
Hypoglycemics: lower blood glucose level. Examples include Insulin and oral
hypoglycemic agents such as Sulfonylurea e.g., chlorpropamide, tolbutamide, glipizide,
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glibenclamide, glimepiride, α-Glucose inhibitors e.g., acarbose, meglitinides e.g., repaglinide,
mitiglinide and nateglinide, thiazolidinediones (Glitazones) e.g., rosiglitazone, pioglitazone,
lobeglitazone, troglitazone, biguanides e.g., metformin; glucophage®, phenformin, buformin,
dipeptidyl peptidase-IV (DPP-IV) inhibitors e.g., sitagliptin, vildagliptin, saxagliptin,
linagliptin, anagliptin, teneligliptin, alogliptin, gemigliptin, dutogliptin, berberine and lupeol.
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Immunologic agents: induce immunity and prevent infectious diseases; stimulate body to
produce antibodies. Examples for such class are Varicella vaccine, MMR vaccine, DPT
vaccine, Hepatitis B vaccine.
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Immunosuppressants: treat and prevent rejection of transplanted organs. Examples
include glucocorticoids, cytostasis, cyclophosphamide, methotrexate, azathioprine,
fluorouracil, antibodies, interferons, infliximab, etanercept, adalimumab, mycophenolic acid,
fingolimod, ciclosporin, tacrolimus and sirolimus.
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Laxatives: loosen and promote normal bowel elimination; relieve constipation. Examples
for such class include bisacodyl, sennosides, magnesium hydroxide; milk of magnesia®,
psyllium, methyl cellulose, polycarbophil calcium, glycerine, sorbitol, lactulose, magnesium
sulfate, castor oil, lubiprostone, cisapride and tegaserod.
Leukotriene receptor antagonist blockers: used for treatment and management of asthma.
Examples include zafirlukast, zileutin and montelukast.
Lipid-lowering agents: this class includes cholesterol-lowering drugs, statins such as
a
atorvastatin, fluvastatin, lovastatin, pitavastatin, pravastatin, rosuvastatin and simvastatin,

niacin, bile-acid resins, fibric acid derivatives (fibrates), Cholesterol absorption inhibitors
ov
(ezetimibe) and omega-3- fatty acids.

Mucolytic agents: break chemical bonds in mucus, lowering the viscosity. Examples
include acetyl cysteine, erdosteine, bromheksin, carbocysteine, guaifenesin and iodinated
glycerol.
Muscle relaxants: produce relaxation of skeletal muscle. Examples include diazepam,
N
metaxalone, orphenadrine, chlorzoxazone and methocarbamol,

Neuroleptic: modifies psychotic behavior (Risperdal, Zyprexa, Stelazine)
Ophthalmic anti-infective agents: treat eye infections. Examples include levofloxacin,

tobramycin, ciprofloxacin, azithromycin, gatifloxacin, natamycin, moxifloxacin, idoxuridine,
chloramphenicol and gentamicin.
Otic preparations: treat ear conditions. Examples include antibiotics, hydrogen peroxide,
isopropyl alcohol, glycerin, boric acid, hydrocortisone, ethyl alcohol, acetic acid,
c.
aminoglycosides antibiotics, aluminum acetate, triamcinolone and dexamethasone.
Platelet inhibitors: inhibit the ability of platelets to adhere to each other; similar to
coagulant. Examples include aspirin, triflusal, clopidogrel, prasugrel, ticagrelor, ticlopidine,
In
vorapaxar, abciximab, tirofiban and dipyridamole.
Selective serotonin reuptake inhibitors (SSRIs): selectively inhibit serotonin reuptake and
result in potentiation of serotonergic neurotransmissions. Examples include fluvoxamine,
paroxetine, fluoxetine; Prozac and sertraline.
Serotonin nonselective reuptake inhibitors (SNRIs): inhibit the reuptake of both serotonin
rs
and norepinephrine. Examples for such class are venlafaxine, desvenlafaxine, duloxetine,
milnacipran, levomilnacipran and sibutramine.
Smoking deterrents: used to manage nicotine withdrawal. Examples include bupropion,
topiramate, varenicline, nicotine and clonidine.
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Thrombolytic agents: dissolve an existing thrombus (clot) when administered soon after
their occurrence. Examples include streptokinase, anistreplase, alteplase and urokinase.
Thyroid hormone agents: increase basic metabolic rate (Triiodothyronine; T3, Thyroxine;
T4)
Vasodilators: produce relaxation of blood vessels; lowers blood pressure. Examples
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include Iisosorbide dinitrate and nitroglycerin.
Vasopressors: produce contraction of muscles of capillaries and arteries; elevate blood
pressure; used to treat allergic reactions (Norepinephrine, Metaraminol)
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Weight control agents: used to manage obesity. Examples include a combination of
phentermine and topiramate, orlistat, lorcaserin, sibutramine, rimonabant, amphetamine,
Phenylpropanolamine, metformin and pramlintide.
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Drug Types
There are four types of drugs: 1-medication, 2-recreational, 3-spiritual and 4-nootropic
[26-35].
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Medication Drugs: A medication or medicine is a drug taken to cure and/or improve any
symptoms of an illness or medical condition, or may be used as preventive medicine that has
future benefits but does not treat any existing or pre-existing diseases or symptoms.
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Medications are classified in various ways. One of the key divisions is between traditional
small molecule drugs, usually derived from chemical synthesis, and biopharmaceuticals
which include recombinant proteins, vaccines, and blood products used therapeutically, gene
therapy and cell therapy.
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Dispensing of medication is often regulated by governments into three categories:

Drug Overview 15
Over-the-counter (OTC): medications which are available in pharmacies and

supermarkets without special restrictions and without a need of prescription. The list of OTC
medicines varies from country to country.
Behind-the-counter (BTC): drugs that are dispensed by a pharmacist without a need for a
doctor's prescription and are available in pharmacies. They are called pharmacy medicines in
c.
the United Kingdom. These medicines are only sold in registered pharmacies, by or under the
supervision of a pharmacist. These medications are designated by the letter P on the label.
The number of medicines available without a prescription varies from country to country.
In
Prescription only medicines (POM): these medications must be prescribed by a licensed
medical professional, usually a physician and are available in pharmacies or clinics.
Medications are typically produced by pharmaceutical companies and are often patented
to give the developer exclusive rights to produce them, but they can also be derived from
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naturally occurring substance in plants called herbal medicine. Those that are not patented (or
their patent has expired) are called generic drugs. Generic drugs can be produced by other
companies without restrictions or licenses from the patent holder. A pharmaceutical drug
(medicine or medication and officially medicinal product) is any chemical substance
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formulated or compounded as a single active ingredient or in combination of other
pharmacologically active substance, it may be in a separate but packed in a single unit pack as
combination product intended for internal, or external or for use in the medical diagnosis,
cure, treatment, or prevention of diseases [36-44].
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Examples of Important OTC Drugs: in the United States, the FDA classified whether
medicines are prescription or nonprescription based on the safety and effectiveness of the
drug if used under a physician care or not. The term prescription (Rx) refers to medicines that
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are safe and effective when used under a doctor's care.
Nonprescription or OTC drugs are medicines that are safe and effective for use without a
doctor's prescription. The FDA also has the authority to decide when a prescription drug is
safe enough to be sold directly to consumers over the counter.
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The regulatory process known as Rx-to-OTC switch is allowing Americans to take a

more active role in their health care. As a result of this process, more than 700 products are
sold as OTC. There are more than 80 classes of OTC drugs, ranging from allergy medicines
to pain relievers to weight loss products [45-47]. OTC medicines vary from country to
country.
a
OTC Drugs for Aches, Pains, and Headaches: OTC pain medicines can help with
headache, arthritis pain, sprains, and other minor joint and muscle problems. Acetaminophen
and nonsteroidal anti-inflammatory drugs (NSAIDs) such as aspirin, ibuprofen and naproxen
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(Figure 1) are used as OTC drugs for pain relief. Acetaminophen (Tylenol) and ibuprofen
(Advil, Motrin) used to reduce fever in children and adults.
N
HN CH3
O OH
O CH3
c.
O
OH
Acetaminophen Aspirin
In
O
CH3 CH3
OH H3C
CH3
O
H3C
rs
HO O
Naproxen Ibuprofen
Figure 1. Chemical structures of acetaminophen, aspirin, naproxen and ibuprofen.
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OTC Drugs for Cold, Sore Throat and Cough: Cold medicines can treat symptoms not
the specific cold viruses. Treatment the cold symptoms make the patient feels better, they
don't cure the cold, but they can bring relief, lighter symptoms, or maybe even shorten the
cold. Using zinc supplements within 24 hours of the start of a cold may reduce the symptoms
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and duration of the cold. Cough medicines include guaifenesin (Figure 2) which helps break
up mucus, menthol throat lozenges which soothe "tickle" in the throat. Liquid cough
medicines with dextromethorphan (Figure 2) suppress the cough (Benylin, Delsym,
Robitussin DM, and Simply Cough, Vicks, and store brands).
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O
H3C
CH3
Pu
O OH
O OH
N CH3
H
a
Guaifenesin Dextromethorphan
OH
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NH
CH3
CH3
Pseudophedrine
N
Figure 2. Chemical structures of guaifenesin, dextromethorphan and pseudoephedrine.

Drug Overview 17
Decongestants help clear a runny nose and relieve postnasal drip. Examples of oral
decongestants include pseudoephedrine (Figure 2) (Contact Non-Drowsy, Sudafed, and store
brands), phenylephrine (Sudafed PE and store brands). Examples of decongestant nasal
sprays are oxymetazoline (Afrin, Neo-Synephrine Nighttime, Sinex Spray), phenylephrine
(Neo-Synephrine, Sinex Capsules) [45-47].
c.
OTC Drugs for Allergy: In general, there is no cure for allergies, but there are several
types of medications available, both OTC and prescription. These medications help ease and
treat annoying symptoms like congestion and runny nose. These allergy drugs include
In
antihistamines, decongestants, combination drugs, corticosteroids, and others. For allergies
antihistamine pills and liquids work well for treating allergy symptoms. Among the
Antihistamines that may cause sleepiness are diphenhydramine (Benadryl), chlorpheniramine
(Chlor-Trimetron) (Figure 3), brompheniramine (Dimetapp), or clemastine (Tavist).
Examples of antihistamines that cause little or no sleepiness are loratadine (Alavert, Claritin,
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Dimetapp ND), fexofenadine (Allegra), cetirizine (Zyrtec) (Figure 3).
O OH
he
O
CH3
N
H3C
N
N
is
N
bl
Cl Cl
Chlorpheniramine Cetirizine
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Figure 3. Chemical structures of chlorpheniramine and cetirizine.
OTC Drugs for Diarrhea, Nausea and Vomiting: Diarrhea, vomiting and nausea are
common complaints that can result from diseases such as gastrointestinal and inflammatory
bowel diseases, conditions such as food allergies, and from usage of antibiotics or other
drugs. The fluid and electrolytes lost during diarrhea and vomiting need to be replaced
promptly. Anti-diarrhea medicines such as loperamide (Imodium) are effective for
a
terminating diarrhea. Medicines that contain bismuth may be taken for mild diarrhea
(Kaopectate, Pepto-Bismol). Rehydration fluids may be used for moderate and severe
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diarrhea (Enfalyte or Pedialyte). For mild nausea and vomiting, liquids and pills for stomach
upset may help (Emetrol; Pepto-Bismol). Rehydration fluids may be used to replace fluids
from vomiting (Enfalyte or Pedialyte). Medicines for motion sickness such as dimenhydrinate
(Dramamine), meclizine (Bonine, Antivert, Postafen, and Sea Legs) can be effective in
nausea and vomiting conditions [45-47].
N
OTC Drugs for Skin Rashes and Itching: Oral antihistamines may help in itching and
allergy conditions. Hydrocortisone cream may help with mild rashes (Cortaid, Cortizone 10).
Anti-fungal creams and ointments may help with diaper rashes and rashes caused by yeast
(nystatin, miconazole, clotrimazole, and ketoconazole) [45-47].
Top Twenty OTC Medications Sold in US: The following are the top twenty OTC
c.
drugs sold in the united states: Advil (ibuprofen), Aleve (naproxen), Cēpacol®
antibacterialmulti-protection mouthwash (cetylpyridinium chloride), Children's Dimetapp
Cold and Cough (brompheniramine maleate, dextromethorphan HBr, and phenylephrine
In
HCl), Claritin (loratadine), Colace (docusate sodium), Cortaid Maximum Strength
(hydrocortisone acetate), Dulcolax (docusate sodium or bisacodyl), Excedrin Extra Strength
(acetaminophen, aspirin, caffeine), Gaviscon (aluminum hydroxide, magnesium carbonate),
Lotrimin® AF Antifungal (miconazole nitrate, Figure 4), Maalox Antacid (aluminum
hydroxide, magnesium carbonate), Midol (ibuprofen), Motrin IB (ibuprofen), Orajel
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Maximum Strength (benzocaine Figure 4), Pepto-Bismol (bismuth subsalicylate), Rolaids®
Multi-Symptom (calcium carbonate, dimethicone or simethicone), Tagamet HB (cimetidine),
Tylenol® (acetaminophen) and Zantac75® (ranitidine hydrochloride, Figure 4) [47].
he
H3C O
+
O N
N -
H3C S O
NH
CH3 Ranitidine
NH
Cl
is
bl
Cl
H2N
O
O CH3 N
Pu
N
Cl Cl
O
Benzocaine Miconazole
Figure 4. Chemical structures of ranitidine, benzocaine and miconazole.

a
Drug Administration
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Drugs, both medicinal and recreational, can be administered by a number of ways. Many
drugs can be administered in a variety of ways rather than just one as the following [48].
Bolus: is the administration of a medication, drug or other compound that is given to raise
its concentration in blood to an effective level. The administration can be given intravenously,
by intramuscular, intrathecal or subcutaneous injection. An intravenous injection can be more
N
difficult to administer than a subcutaneous or intramuscular injection because inserting a

needle or catheter into a vein may be difficult, especially if the person is obese. The
Drug Overview 19
subcutaneous route is used for many protein drugs because such drugs would be destroyed in
the digestive tract if they are taken orally.
Inhaled: Inhaled medications can be absorbed quickly, and act both locally and
systemically. They are breathed into the lungs as an aerosol or dry powder. This includes
smoking a substance. Usually, this method of administration is used to administer drugs that
c.
act specifically on the lungs, such as aerosolized antiasthmatic drugs in metered-dose
containers (called inhalers) and gases used for general anesthesia.
Injected: They can be as a solution, suspension or emulsion. They are given either
In
intramuscular, or intravenous, or intraperitoneal or intraosseous. Intravenous administration is
the best way to deliver a precise dose quickly and in a well-controlled manner throughout the
body. The intramuscular route is preferred over the subcutaneous route when larger volumes
of a drug are needed.
Insufflation: snorted into the nose. Drugs administered by this route generally work
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quickly. Some of them irritate the nasal passages.
Orally: The oral route is the most common route of drug administration. It may be in the
form of a liquid or solid (tablets, capsules, syrup, emulsions or powders) that is absorbed
through the intestines. The advantages of this route are its convenience, cheapest, easy to use,
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safe and acceptable. While the disadvantages of this route include less amount of a drug
reaches the target tissue, some of the drug is destroyed by gastric juices, the drug‘s absorption
is slow, gastric irritation may be caused by the drug, objectionable in taste and discoloration
of teeth.
Rectally: Drugs in solid forms such as suppositories or in liquid forms such as enema are
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given by this route and absorbed by the rectum or colon. This route is mostly used in old
patients and pediatrics that have difficulties in swallowing. Drugs may have local or systemic
actions after absorption. The advantages of this route are preferred in unconscious or
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uncooperative patients, avoiding nausea or vomiting can be achieved using this route and
drugs are not destroyed by enzymes (avoid hepatic first pass metabolism, drugs given by
rectal route have 50% first pass metabolism). While the disadvantages are patients dislike
suppositories or may be not acceptable by the patients. Locally acting drugs include glycerin
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and bisacodyl suppository and systemic acting drugs include indomethacin (anti-
inflammatory) and aminophylline (bronchodilator).
Sublingually: drugs are diffused into the blood through tissues under the tongue.
Topically: usually as a cream or ointment. A drug administered in this manner may be
given to act locally or systemically.
Vaginally: Some drugs may be administered vaginally to women as a solution, tablet,
cream, gel, suppository or ring. The drug is slowly absorbed through the vaginal wall.
a
Suppositories are primarily used to treat vaginal infections. This route is often used to give
estrogen to women during menopause to relieve vaginal symptoms such as dryness, soreness
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and redness.
Recreational Drugs: Recreational drugs are chemical substances that affect the central
nervous system (CNS) such as opioids or hallucinogens. They may be used for effects on
perception, consciousness, personality and behavior. They are taken for enjoyment, or leisure
purposes, rather than for medical reasons. Alcohol, nicotine, and caffeine are the most widely
N
consumed psychotropic drugs worldwide. Some drugs can cause addiction and habituation
and all of these drugs have side effects [26-35]. The use of these drugs is incredibly common
around the world and it very often leads to disaster and crime.
Spiritual Drugs (Entheogen): Spiritual drugs are chemical substances, typically of plant
origin or may be synthesized, that are ingested to produce unordinary state of consciousness
for religious or spiritual purposes. These drugs can cause severe damage to mental or physical
health. There are a number of drugs that are said to induce spiritual experiences including
lysergic acid diethylamide (LSD) (Figure 5), peyote, ayahuasca, psilocybin (magic
c.
mushrooms), ecstasy, marijuana, mescaline and etc. [26-35].
CH3
In
O N CH3
O
HN OH
rs
N
CH3
H
Cl
S N
O O CH
he
HN 3
Lysergic acid diethylamide Tianeptine
CH3
is
NH2 Amphetamine
Figure 5. Chemical structures of lysergic acid diethylamide, tianeptine and amphetamine.

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Nootropic Drugs: Nootropic drugs also referred to as smart drugs, memory enhancers,
neuro enhancers, cognitive enhancers, and intelligence enhancers, are drugs, supplements,
nutraceutical, and functional foods that improve one or more aspects of mental function, such
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as working memory, motivation, and attention. These drugs are used primarily to treat people
with cognitive or motor function difficulties attributable to such disorders as Alzheimer's
disease, Parkinson's disease, Huntington's disease and ADHD. Examples for such drugs
include stimulants (amphetamine, Figure 5), methylphenidate, eugeroics (armodafinil and
modafinil), xanthines and nicotine. Certain stimulants will enhance cognition in the general
population, but only when used at low (therapeutic) concentrations. Relatively high doses of
stimulants will result in cognitive deficits. Other examples are phosphatidylserine, tianeptine
a
(Figure 5), valproate and isoflavones [26-35].

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Drug Interactions
A drug interaction occurs when a drug affects the activity of another drug when both are
administered together. Drug interactions can result in unwanted side effects, reduce the
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effectiveness of a medicine or possibly increase the action of a particular medicine or produce

a new effect that neither produces on its own. Drug interactions are usually divided into four
Drug Overview 21
groups: antagonism (drug's reduces or blocks the effect of another), synergism (drug's effect
is increased), potentiation (drug A boosts the effects of drug B), and interaction with
metabolism. There are different risk factors of drug interactions: age (elderly or young),
multiple disease, multiple drug therapy, renal and liver impairment, narrow therapeutic index
(e.g., Insulin, Lithium, Digoxin, Warfarin, Phenytoin, Theophylline, Phenobarbitone) and
c.
enzyme inhibitors or inducers. The outcomes of drug interactions might be loss of therapeutic
effect, toxicity, unexpected increase in pharmacological activity, beneficial effects e.g.,
additive and potentiation (intended) or antagonism (unintended) and chemical or physical
In
interaction (e.g., I.V incompatibility in fluid or syringes mixture). Drug interactions may
result from pharmacokinetic interactions (absorption, distribution, metabolism, and excretion)
or from interactions at drug receptors. These interactions may occur out of accidental misuse
or due to lack of knowledge about the active ingredients involved in the relevant substances.
Interactions may also exist between drugs and foods (drug-food interactions), as well as
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drugs and medicinal plants or herbs (drug-plant interactions). Drug-food interactions can
happen with both prescription and OTC medicines. Not all medicines are affected by food,
but many medicines can be affected by what we eat and when we eat. An example of a drug-
food interaction; patients who take monoamine oxidase inhibitors (antidepressants) should
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not take food containing tyramine (found in cheese) because hypertensive crisis may occur
[49-53].
The pharmacological interactions of drugs are important to know and understand. For
example; if a person is taking two drugs and one increases the effect of the other it is possible
that an overdose may occur (toxicity occurs). The interaction of the two drugs may also
is
increase the risk of side effects. On the other hand, if the action of a drug is reduced it may
reduce or diminish any therapeutic effect because of under dosage. Nevertheless, sometimes
the interactions may improve the therapeutic effect. Examples of this include the use of
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codeine with paracetamol to increase the analgesic effect of the medication. The combination
of clavulanic acid with amoxicillin is another example to overcome the bacterial resistance to
antibiotics. The interactions that are important are those that have negative effects on patients.
The risk that a pharmacological interaction will cause is increased as a function of the number
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of drugs administered to a patient at the same time.

As mentioned before, it is possible that an interaction will occur between a drug and
another substance present in the body (such as food or alcohol). In certain specific situations a
drug may even react with itself (hypersensitivity).
In other situations, the interaction does not involve any effect on the drug. In certain
cases, the presence of a drug in an individual's blood may affect certain types of laboratory
analysis (analytical interference).
a
It is also possible for interactions to occur outside the organism before the administration
of a drug. This can occur when two drugs are mixed together. Some classic examples of this
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type of interaction include thiopentone and suxamethonium (Figure 6) which should not be
placed in the same syringe and the same is also true for benzylpenicillin and heparin.
N
CH3
O
Et
O CH3
HN CH3 + CH3
c.
H3C + O N
N O CH3
S N O H3C
H CH3 O
In
Thiopentone Suxamethonium
Figure 6. Chemical structures of thiopentone and suxamethonium.
Drug interactions may be due to various processes such as alterations in the

pharmacokinetics of the drug (alterations absorption, distribution, metabolism, and excretion
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(ADME)) or/and interactions in the pharmacodynamic properties of the drug (co-
administration of a receptor antagonist and an agonist for the same receptor).
Pharmacodynamics is related to the pharmacological activity of the interacting drugs e.g.,
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synergism, antagonism, altered cellular transport, effect on the receptor site [49-53].
Types of Drug Interactions

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As mentioned before, drug interaction is the modification of the effect of one drug (the
object drug) by the prior concomitant administration of another (precipitant drug). There are
different types of drug interaction: (i) pharmacokinetic interactions, (ii) pharmacodynamic
bl
interactions, (iii) drug-nutrient interactions, (iv) drug-disease interactions and (v)
pharmaceutical interactions. The outcomes of drug interactions are loss of therapeutic effect,
toxicity, unexpected increase in pharmacological activity, beneficial effects such as additive
and potentiation (intended) or antagonism (unintended) and chemical or physical interaction
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such as I.V incompatibility in fluid or syringes mixture. There are essentially two types of
drug interactions: pharmacodynamic and pharmacokinetic.
Pharmacokinetic Interactions
a
Pharmacokinetic interactions involve the effect of a drug on another and the drugs
absorption, distribution, metabolism and excretion are the important factors playing roles in
such interactions. Pharmacokinetic interactions are those in which one drug results in an
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alteration (increase or decrease) of the concentration of another drug in the system. Different
parameters can be affected by pharmacokinetic interactions, including a drug‘s
bioavailability, volume of distribution, peak level, clearance and half-life. Such changes can
lead to changes in drug plasma concentrations and ultimately increase the risk of side effects
or diminish the efficacy of one or more drugs. Pharmacokinetic interactions are more
N
complicated and difficult to predict because the interacting drugs often have unrelated
actions.
Drug Overview 23
The paragraphs below are a brief summary and some examples of the four
pharmacokinetic processes that may be involved individually or collectively in various drug
interactions.
Absorption: Drug absorption refers to the route or method by which the drug reaches the
blood supply (the movement of drugs into the body depends on how the drug is
c.
administered). There are three areas in which interactions might occur at the level of drug
absorption. One drug may affect the rate and/or extent of absorption of other drugs if it alters
GI motility, gastric pH or chemically binds with other drugs to form insoluble, non-
In
absorbable complexes.
Alteration of GIT absorption can occur as a result of either (1) alteration of pH (such as
antacids and H2 antagonists decrease the pH and thus decrease the absorption of
Ketoconazole, (2) alteration bacterial flora (e.g., In 10% of patients receive digoxin about
40% or more of the administered dose is metabolized by the intestinal flora). If antibiotics are
rs
administered with digoxin, a toxicity might occur as digoxin concentration increases because
antibiotics kill a large number of the normal flora of the intestine, (3) formation of drug
chelates or complexes (e.g., tetracycline interacts with iron preparations, milk products and
antacids. Aluminum or magnesium hydroxides decrease the absorption of tetracycline by 85%
he
due to chelation, (4) drug induced mucosal damage (e.g., antineoplastic agents such as
cyclophosphamide, vincristine, procarbazine which inhibit the absorption of several drugs
such as digoxin) and (5) altered GIT motility (e.g., metoclopramide (antiemetic), increases the
toxicity of cyclosporine because it increases its absorption due to the increase of stomach
empting time).
is
Displaced protein binding (distribution): Distribution is the movement of the drugs
around the body. Once the drug is absorbed, it is rapidly distributed around the blood supply,
and then slowly distributed to the various tissues and organs. The rate and extent of the drug
bl
distribution depends on the blood flow, tissue size, and affinity of the drug to plasma protein
(albumin) and tissue components, and permeability of tissue membranes. The most likely
bound drugs are capable to displace others. The free drug is increased by displacement by
another drug with higher affinity. For example, drugs that are highly bound to plasma protein
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such as phenytoin, tolbutamide and warfarin (Figure 7) can displace other agents with lower
affinity to plasma protein such as aspirin, sulfonamides and phenylbutazone. Warfarin and
methotrexate bound to albumin and plasma protein in the blood and they will be unavailable
to interact with their targets. When another drug is taken with these medications which have
the ability to compete for plasma protein binding (e.g., sulphonamide), a certain percentage of
previously bounded drug (warfarin or methotrexate) is released, thus increasing the free form
of the drug and consequently its effect.
a
Altered metabolism: the effect of one drug on the metabolism of the other is well
documented. The liver is the major site of drug metabolism but metabolism can occur in other
ov
organs such as WBC, skin, lung, and GIT. Cytochrome P450 family is the major
metabolizing enzyme in phase I (oxidation process). Therefore, the effect of drugs on the rate
of metabolism of others can involve the followings:
(a) Enzyme induction; a drug may induce the enzyme that is responsible for the
metabolism of another drug or even itself such as in the case of carbamazepine (antiepileptic
N
drug, Figure 8) which increases its own metabolism. Phenytoin increases hepatic metabolism
of theophylline (Figure 8), leading to a decrease in the latter‘s concentrations level and
reduces its therapeutic action. Enzyme induction involves protein synthesis. Therefore, it
needs time up to 3 weeks to reach a maximal effect.
CH3
c.
OH O
O
H3C S NH CH3
In
O NH
O O O
Tolbutamide Warfarin
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Figure 7. Chemical structures of tolbutamide and warfarin.
H O
he
N H
O H3C N
N
N N
O H N
O N
O
is
H2N CH3
Carbamazepine Phenytoin Theophylline
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Figure 8. Chemical structures of carbamazepine, pheytoin and theophylline.
(b) Enzyme inhibition; it is a decrease of the rate of metabolism of a drug by another one.
This will lead to an increase of the concentration of the target drug and consequently to an
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increase of its toxicity. Inhibition of the enzyme may be due to the competition on its binding
sites. When an enzyme inducer such as carbamazepine is administered with an inhibitor such
as verapamil (Figure 9), the effect of the inhibitor will be predominant. Erythromycin inhibits
the metabolism of astemazole and terfenadine, thus increases their serum concentrations and
leads to an increase of the life threatening cardio-toxicity. Another example is omeprazole
(Figure 9) which inhibits the oxidative metabolism of diazepam (Figure 9).
Excretion: Renal excretion (active tubular secretion); it occurs in the proximal tubules, a
a
portion of renal tubules. The drug combines with a specific protein to pass through the
proximal tubules. When a drug has a competitive reactivity to the protein that is responsible
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for the active transport of another drug this will reduce a drug excretion increasing its
concentration and hence its toxicity. For example, probenecid (Figure 10) decreases tubular
secretion of methotrexate (Figure 10).
Passive tubular reabsorption; excretion and reabsorption of drugs occur in the tubules by
passive diffusion which is regulated by concentration and lipid pharmacodynamics
N
interactions solubility. Ionized drugs are reabsorbed in a lower extent than non-ionized ones.
Sodium bicarbonate increases lithium clearance and decreases its action. Antacids increase
salicylates clearance and decrease their action [54-58].
Drug Overview 25
H3C CH3
O CH3
N O
O O
N CH3 Cl
CH3 N
c.
H3C O
CH3 N
CH3
In
Verapamil Diazepam
H3C O CH3
O N CH3
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H3C
S N
N O
H Omeprazole
O
O he
Figure 9. Chemical structures verapamil, diazepam and omeprazole.
is
H3C S
N
O
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CH3 OH Probenecid
HO O
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O
OH
NH2 NH
N O
a
N N
CH3
H2N N N Methotrexate
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Figure 10. Chemical structures of probenecid and methotrexate.

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Pharmacodynamic Interactions
Pharmacodynamic interactions are alteration of the dug action without a change in its
serum concentration by pharmacokinetic factors. The Pharmacodynamics interactions types
are:
c.
A synergism (1+1=3): When the therapeutic or toxic effects of two drugs are greater than
the effect of an individual drug, it is called synergism. Drug synergism is of two types:
In
additive effect and potentiation. Propranolol + verapamil is synergistic or additive effect
Additive effect (1+1=2): when the net effect of two drugs used together is equal to the
sum of the individual drug effects, the drugs are said to have an additive effect. For example,
the combination of a thiazide diuretic and a beta adrenergic blocking drug used for the
treatment of hypertension.
rs
Potentiation (1+0=2): when the net effect of two drugs used together is greater than the
sum of the individual drug effects, the drugs are said to have potentiation effect. For example,
the combination of sulfamethoxazole (Figure 11) and trimethoprim (Figure 11) used as
antimicrobial agents.
O
S
N
N O
CH3
he H2N
N
N NH2
O
O
CH3
CH3
is
O
H O
H2N CH3
Sulfamethoxazole Trimethoprim
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Figure 11. Chemical structures of sulfamethoxazole and trimethoprim.
Antagonism (1+1=0 or 0.5): the effect of one drug can be reduced or abolished by the
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presence of another drug and this effect is termed drug antagonism. Drug antagonism is of
three types- chemical, physiological and pharmacological. Physiological and pharmacological
antagonisms involve the interaction of an agonist with an antagonist.
Chemical antagonism; when a drug antagonizes the effect of another drug by simple
chemical reaction without activating a receptor. For example, antacid neutralizes the gastric
acid. Physiological antagonism; when the physiological effect of a drug is antagonized by
a
another drug by acting on two different types of receptors. For example, acetylcholine causes
contraction of an intestinal smooth muscle by acting on muscarinic choline-receptors.
Whereas this action of acetylcholine is antagonized (that is relaxation of the intestinal smooth
ov
muscle) by adrenaline. Pharmacological antagonism; when a drug antagonizes the effect of

another drug by acting on the same receptor it is called pharmacological antagonism.
Pharmacological antagonism is of two types: competitive and noncompetitive.
Competitive antagonism; competitive antagonism is reversible. The inhibitory effect of
an antagonist is overcome by using large amount of agonist. Here, both, the agonist and
N
antagonist compete for the same receptor and are able to displace each other at the receptor
site. For example, acetylcholine causes contraction of intestinal smooth muscle. Atropine
Drug Overview 27
(Figure 12) blocks the effect of acetylcholine (Figure 12). When a low concentration of an
agonist is plotted against the responses, a sigmoid shaped curve will be obtained. The
maximum response of the agonist is obtained in the presence of competitive antagonist. The
dose-response curve remains parallel but is shifted to the right.
c.
H3C N H
HO
In
H O CH3
O CH3
+
N
O H3C O CH3
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Atropine Acetylcholine
Figure 12. Chemical structures of atropine and acetylcholine.
Noncompetitive antagonism; the maximum response of an agonist in the presence of
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antagonist is reduced. The inhibitory effect of a drug is not overcome by using large amount
of agonist [48, 54, 57, 59-63].
Drug-Nutrient Interactions
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Nutrition can affect the body's response to drugs; conversely, drugs can affect the body's
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nutrition. Food, beverages, and dietary supplements alter the effects of drugs the person takes.
Foods can enhance, delay, or decrease drug absorption. The presence of food in the digestive
tract may reduce the absorption of a drug. Often, such interactions can be avoided by taking
the drug 1 hour before or 2 hours after eating. Dietary supplements are regulated as foods, not
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as drugs, so they are not tested comprehensively. However, they may interact with
prescription or OTC drugs. People who take dietary supplements should inform their doctors
and pharmacists, so that interactions can be avoided. For instance, taking alcohol with
metronidazole can cause flushing, headache, palpitations, and nausea and vomiting. Drugs
such as terfenadine, cyclosporine and felodipine interact with grapefruit juice. Other food,
such as orange juice, coffee, or mineral water, may reduce the absorption and effectiveness of
these drugs. Anticoagulants interact with foods containing high concentrations of vitamin K
a
(such as broccoli, brussels sprouts, spinach, and kale).

Such foods may reduce the effectiveness of anticoagulants such as warfarin and increase
ov
the risk of clotting. Intake of such foods should be limited, and the amount consumed daily
should remain constant. Digoxin interacts with oat meals, the fiber in oat meal and other
cereals, when consumed in large amounts, can interfere with the absorption of digoxin.
Tetracycline interacts with calcium or foods containing calcium, such as milk and other dairy
products. These foods can reduce the absorption of tetracycline which should be taken 1 hour
N
before or 2 hours after meals [64-67].

Drug-Disease Interactions
Sometimes, drugs that are helpful in one disease are harmful in another. Drug-disease
interactions can occur in any age group but are common among old people, who tend to have
more diseases. For example, some beta-blockers taken for heart disease or high blood
c.
pressure can worsen asthma. This interaction makes it hard for people with diabetes to tell
when their blood sugar is too low. Some drugs taken to treat a cold may worsen glaucoma.
People should tell their doctor all of the diseases they have before the doctor prescribes a new
In
drug [68-72].
Pharmaceutical Interactions
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Pharmaceutical interactions occur when two drugs react chemically or physically during
administration or absorption so that the amount of drug available for absorption (of one or
both drugs) is altered. Pharmaceutical interactions also occur as a result of mixing two or
more antagonistic substances and an undesirable product is formed which may affect the
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safety, efficacy and appearance of pharmaceutical preparation. The types of interactions are:
(i) physical interaction, examples immiscibility, insolubility, precipitation and liquefaction,
(ii) chemical interaction; (1) tolerated: the chemical interaction can be minimized by
changing the order of mixing or mixing the solutions in dilute forms but no alteration is made
in the formulation, (2) adjusted: the chemical interaction can be prevented by an addition or
is
substitution of one of the reacting ingredients of a prescription with another of equal
therapeutic value [73-76].
Serious loss of potency can occur from incompatibility between an infusion fluid and a
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drug that is added to it. Similarly, an addition of more than one drug to the same infusion
fluid may result in interactions which cause loss of activity. The immediate effect of soluble
insulin is reduced if it is drawn up with potassium zinc insulin in the same
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syringe or drip [73-76].

Examples of pharmaceutical interactions are mixture of thiopentone and suxamethonium
(precipitation), mixture of diazepam and infusion fluid (precipitation), mixture of phenytoin
and infusion fluid (precipitation), mixture of heparin and hydrocortisone (inactivation of
heparin), mixture of kanamycin and hydrocortisone (inactivation of kanamycin) and mixture
of carbenicillin and gentamicin (inactivation of gentamicin). Table 2 illustrates some
examples of drug interactions.
a
Table 2. Examples of some important drug interactions

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Interaction Effect Time to Effect Recommendations

SSRIs with selegiline or Hypertensive crisis Soon after Avoid.
nonselective monoamine initiation
oxidase inhibitor
SSRIs with tramadol Seizures; serotonin Any time Monitor the patient for signs
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syndrome and symptoms of serotonin

syndrome
Drug Overview 29

SSRIs with St. John's wort Serotonin syndrome Any time Avoid
SSRIs with naratriptan, Serotonin syndrome Possibly after Avoid. monitor the patient
rizatriptan, sumatriptan or initial dose for signs and symptoms of
zolmitriptan serotonin syndrome
Lovastatin with warfarin Warfarin effects Any time Monitor INR.
c.
increased
SSRIs with tricyclic TCA level increased Any time Monitor for anticholinergic
antidepressant (TCA) excess and consider lower
dosage of TCA
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Warfarin with ciprofloxacin, Warfarin effects within 1 week Use another antibiotic
clarithromycin, increased
erythromycin,
metronidazole
Warfarin with Bleeding & INR Any time Reduce the dose of
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acetaminophen increased acetaminophen and monitor
INR.
Warfarin with aspirin Bleeding & INR Any time Reduce the dose of aspirin
increased to 100/ day and monitor
INR.
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Warfarin with NSAIDs Bleeding & INR Any time Avoid combination or use a
increased cyclooxygenase-2 inhibitor
instead of Cox-1 inhibitor
and monitor INR.
Fluoroquinolones with Fluoroquinolones Any time Space administration by 2 -4
is
sucralfate absorption decreased hr.
Carbamazepine with Carbamazepine levels within 1 week Monitor carbamazepine
cimetidine, erythromycin, Increased levels
clarithromycin or
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fluconazole
Phenytoin with cimetidine, Phenytoin levels within 1 week Monitor phenytoin levels
erythromycin, increased
clarithromycin or
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fluconazole
Phenobarbital with Phenobarbital levels within 1 week Monitor phenobarbital
cimetidine, erythromycin, increased levels
clarithromycin or
fluconazole
Phenytoin with rifampin Phenytoin levels within 1 week Monitor phenytoin levels.
decreased
Phenobarbital with rifampin Phenobarbital levels within 1 week Monitor phenobarbital
a
decreased levels.
Carbamazepine with Carbamazepine levels within 1 week Monitor carbamazepine
rifampin decreased levels.
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Lithium with NSAID or Lithium levels Any time Decrease lithium dosage by
diuretic increased 50% and monitor lithium
levels
Oral contraceptive with Effectiveness of Any time Avoid combination or use
rifampin contraception contraceptive pill with a
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decreased higher estrogen or use

different method of
contraception
Table 2. (Continued)

antibiotics contraception another contraceptive
c.
decreased
troglitazone contraception contraceptive pill with a
decreased higher estrogen or use
In
different method of
contraception
Cisapride with Cisapride metabolism within 1 week Avoid. Or use
erythromycin, inhibited metoclopramide
clarithromycin, fluconazole,
itraconazole, ketoconazole,
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nefazodone
Cisapride with class IA or Prolongation of QT Any time Avoid. Or use
class III antiarrhythmic interval along with metoclopramide.
agents, tricyclic arrhythmias
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antidepressants or
phenothiazine
Sildenafil (Viagra) with Acute hypotension Directly after Absolute contraindication
nitrates taking
sildenafil
Sildenafil with cimetidine, Sildenafil levels Any time Initiate sildenafil at a 25-mg
is
erythromycin, itraconazole increased dose
or ketoconazole
HMG-CoA reductase Any time Rhabdom- Avoid combination
inhibitor with niacin, yolysis
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gemfibrozil, erythromycin
or itraconazole
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Prescription or Nonprescription Drugs

According to laws, drugs are divided into two groups: prescription drugs and
nonprescription drugs (OTC). Prescription drugs are used only under medical supervision and
dispensed only with a prescription from a licensed medical professional (physician, dentist or
veterinarian). Nonprescription drugs are used without medical supervision (such as aspirin)
a
and are sold as OTC. In the United States, the FDA is the government agency that decides
which drugs require a prescription and which don't require prescription [77-80].
Dietary supplements do not require the FDA approval before marketing; thus their safety
ov
and efficacy standards are different and not the same as prescription or OTC drugs because
these products are not classified as drugs. Dietary supplements include medicinal herbs and
nutraceutical which given as supplement to the diet. These products may contain vitamins,
amino acids, minerals, and herbs or other plant-derived material. They can act in the same
way as a drug does in the body and may cause health problems if not used correctly or if
N
taken in large amounts. These products may not claim to treat specific medical conditions
because they do not meet the FDA standards for safety and efficacy [77-80].
Drug Overview 31
Drug Names
Drugs have three or more names including a chemical name, brand or trade name
(proprietary, given by the pharmaceutical company it is developed by), and generic or
common name (nonproprietary or official, scientific name, named for the active ingredient of
c.
the medicine). The chemical name is assigned according to rules of nomenclature of chemical
compounds. The brand name is always capitalized and is selected by the manufacturer. The
generic name refers to a common established name irrespective of its manufacturer. For
In
example, sildenafil is the generic name of a medicine used to treat erectile dysfunction.
However, the company that makes sildenafil, Pfizer, sells it under the brand name Viagra. In
most cases, a drug bearing a generic name is equivalent to the same drug with a brand name.
Some knowledge of drug names can help in understanding drug product labels. The names of
medicines can often be confusing, as the same medicine can sometimes be called differently.
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The chemical name describes the atomic or molecular structure of the drug. The chemical
name is usually too complex and cumbersome for general use. So an official body assigns a
generic name to a drug. The generic names for drugs of a particular type (class) usually have
the same ending. For example, the names of all beta-blockers, which are used to treat such
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disorders as high blood pressure, end in "lol" such as metoprolol and propranolol.
The trade name is chosen by the pharmaceutical company that manufactures or
distributes the drug. Patented drugs are usually sold under a trade name. Generic versions of
trade-name drugs manufactured after expiration of the pharmaceutical company's patent may
be sold under the generic name (for example, ibuprofen) or under the manufacturer's own
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trade name (for example, Advil) [81-84].
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Drug Development
Before a drug is tested in human, the drug should be tested in a laboratory and animals to
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determine how the drug works and to evaluate its safety in humans. Drug Development is the
process of bringing a new drug to the market after identification of the lead compound
through a drug discovery process. Drug development includes pre-clinical research where the
experiments are conducted in microorganisms/animals and clinical trials where studies are
carried out on humans. The drug development process may include obtaining an approval
from regulatory bodies to market the drug. The drug discovery process begins by focusing on
specific diseases and patient needs. Researchers search for biological targets within the body
a
that play a role in a given disease. Targets can be part of the body (such as a protein, receptor,
or gene) or foreign (such as a virus or bacteria). Researchers identify, design, and synthesize
promising molecules, screening perhaps tens of thousands of compounds, to assess their
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effect on the relevant biological targets. Molecules that have the desired effect on the target
and meet other design criteria become ―lead‖ molecules that go on to the next phase of
development.
The structure of the lead compound is usually modified many times to optimize its
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specificity and selectivity to target site, its potency, efficacy, effect, safety, stability,
absorption, pharmacokinetics and pharmacodynamics properties. The structure modification
of the lead compound is known as structure activity relationship (SAR). In general, SAR also
overcome the problems associated with certain drugs such as physicochemical properties
(solubility, acidity/basicity, reactivity, binding affinity), pharmacokinetics (absorption,
distribution, metabolism, excretion), pharmacodynamics (onset of action, duration of action),
pharmaceutics (formulation, stability) and pharmacological (effect, side effects, mode of
action) in order to have optimum drugs that are suitable for clinical uses. These factors
c.
involve what the body does to the drug and what the drug does to the body.
Ideally, when a drug is highly selective for its target site it has minimal or no side effects.
The drug should also be highly potent and effective, thus low doses are used in order to
In
minimize the side effects of the drug. The drug should be effective when taken by mouth,
absorbed well from the digestive tract, and reasonably stable in body tissues and fluids so
that, ideally, one dose a day is adequate.
During a drug development, standard or average doses are determined. However, people
respond to drugs differently. Many factors must be considered when doctors determine the
rs
dose for a particular person, including age, weight, genetic make-up, and the presence of
other disorders, affect drug response. Development of new drugs is a complex and costly
process. It takes an average of 10 years and about $950 million to get a new drug from the
laboratory to the market. Only one in 1000 compounds which begin laboratory testing will
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make it to human testing [85-94].
Early development: After a drug that may be useful in treating a disorder is identified or
designed, it will undergo extensive study on animals. Early development gathers information
about how the drug works, it‘s effectively, and what toxic effects it produces, including
possible effects on reproductive capacity and the health. However, little will be known about
is
the safety, toxicity, pharmacokinetics and metabolism of the drug in humans. The pre-clinical
study is the function of drug development to assess all of these parameters prior to human
clinical trials. Many drugs are rejected at this stage because they are shown to be too toxic or
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not effective.
If a drug seems promising after early development, a program describing the clinical
study must be approved by an appropriate institutional research board (IRB) and an
investigational new drug application is filed with the FDA. If the FDA approves the
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application, the drug is allowed to be tested in people (a phase called clinical studies) [85-94].
Clinical studies: clinical studies involve three or four steps. These studies occur in
several phases and only in volunteers who have given their full consent.
Phase I trials determine safety and dosing usually in healthy volunteers (20 to 80). The
investigation in Phase I is to evaluate the safety and tolerability of the drug as well as its
pharmacokinetic and pharmacodynamic properties. In phase I, different amounts of the drug
are given to a small number of healthy, young, usually male people to determine the dose at
a
which toxicity first appears.

Phase II trials are used to get an initial reading of efficacy and further explore safety in
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small numbers of sick patients (100 to 500 patient volunteers). In phase-II, safety and
tolerability, pharmacokinetic and pharmacodynamic properties, efficiency and dosage to
effect relationship are investigated. Phase II evaluates what effect the drug has on the target
disorder and what the right dose might be. Different amounts of the drug are given to up to
100 people who have the target disorder to see whether there is any benefit. Just because a
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drug is effective in animals in early development does not mean it is effective in people.
Phase III trials are large, pivotal trials to determine safety and efficacy in sufficiently
large number of patients (up to 1000 or more patient volunteers). In this phase, the drug is
Drug Overview 33
tested in a much larger (often hundreds to thousands, 300-30,000) group of people who have
the target disorder to monitor reaction to long term drug use. These people are selected to be
as similar as possible to the people who might use the drug in their life. The drug's
effectiveness is studied further, and any new side effects are noted. Phase III tests usually
compare the new drug to standard drug or to placebo, or both in multicenter and multinational
c.
trials. In addition to determining a drug's effectiveness, studies in people focus on the type
and frequency of side effects and on factors that make people susceptible to these effects
(such as age, sex, other disorders, and the use of other drugs). The overall aim of phase III is
In
risk-benefit evaluation. The outcome of phase III studies is crucial for the decision taking of
the regulatory authorities.
Approval: After extensive study and testing, a candidate drug is submitted for regulatory
approval. The decision of the regulatory body determines whether or not the drug can be
marketed to patients for approved uses. The review process usually takes 6 -24 months or
rs
longer. If studies indicate that the drug is effective and safe, a new drug application is filed
with the FDA, which reviews all the information and decides whether the drug is sufficiently
effective and safe to be marketed. If the FDA approves, the drug becomes available for use.
The whole process usually takes about 10 years. On average, only about 5 out of 4,000 drugs
he
studied in the laboratory are studied in people, and only about 1 out of 5 drugs studied in
people is approved and prescribed. Overall drug development process on average to bring one
drug to market takes 12-15 years. Pre-clinical testing takes 1-3 years, on average 18 months.
Clinical research (phase I-III) takes 2-10 years, on average 5 years. The drug development
phase is significantly more expensive in terms of time and money than either lead discovery
is
or drug design and many drugs will fail during the wayside. On average, for every 10000
synthesized structures during a drug design, 500 will reach animal testing, 10 will reach phase
I clinical trials and only 1 will reach the market place.
bl
Phase IV (post marketing): individuals may respond quite differently to the same
medication. Thus, after a new drug is approved, the manufacturers continue monitor the use
of the drug and promptly report any additional, previously undetected side effects to the FDA.
Usually approved medications have been subjected to extensive testing for safety and
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efficacy. But even after medications are approved for general use, companies continue to
collect product-safety information and monitor the safety profile of all products. In fact, the
monitoring increases over time, through the collection of information from ongoing clinical
studies, spontaneous adverse-event reports voluntarily reported directly from healthcare
providers, and patients using the medicine. The FDA may withdraw approval if new evidence
indicates that a drug may cause severe side effects [85-94].
Placebos: Dosage form is made to look exactly like a real drug but do not contain an
a
active ingredient (inactive), usually contains sugar or starch used in research studies. Despite
there being no active ingredients, some people who take a placebo feel better. Some others
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develop side effects. This phenomenon, called the placebo effect. The placebo effect is
mainly on symptoms rather than the actual disease.
When a new drug is being developed, investigators conduct studies to compare the effect
of the drug with that of a placebo because any drug can have a placebo effect, unrelated to its
action. The true drug effect must be distinguished from a placebo effect. Typically, half the
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study's participants are given the drug, and half are given an identical-looking placebo.
Ideally, neither the participants nor the investigators know who received the drug and who
received the placebo.
When the study is completed, all changes observed in participants taking the active drug
are compared with those in participants taking the placebo. The drug must perform
significantly better than the placebo to justify its use [95-96].
c.
Drug Effectiveness and Safety
The main goals of drug development are effectiveness and safety, however, there are
In
three main issues involved in the drug development process: (i) the drug has to be tested to
ensure that it is not only safe and effective, but can be administered in a suitable fashion. This
step involves preclinical and clinical trials to test toxicity, drug metabolism, stability,
formulation, and pharmacological aspects, (ii) there are the various patenting and legal issues
and (iii) the drug has to be synthesized in ever-increasing quantities for testing and
rs
manufacturing. All drugs can harm as well as help, safety is relative, and this depends upon
the dose or quantity of the drug. The difference between the usual effective dose and the dose
that causes severe or life-threatening side effects is called the margin of safety. A wide
margin of safety is desirable, but when treating a dangerous condition or when there is no
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other alternatives, a narrow margin of safety must be accepted. The most useful drugs are
effective and, for the most part, safe. Penicillin is such a drug. Except for people who are
allergic to it, penicillin is nontoxic, even in large doses. On the other hand, barbiturates,
which were once commonly used as sleep aids, can interfere with breathing, lower blood
pressure, and cause death if taken in excess.
is
Sometimes it is difficult to design effective drugs with a wide margin of safety and few
side effects. Consequently, some drugs must be used even though they have a very narrow
margin of safety. For example, warfarin, which is taken to prevent blood clotting, can cause
bl
bleeding, but it is used when the need is so great that the risk must be tolerated. Clozapine is
another example. This drug often helps people with schizophrenia when all other drugs have
proved ineffective. But clozapine has a serious side effect: it can decrease the production of
white blood cells, which are needed to protect against infection. Because of this risk, people
Pu
who take clozapine must have their blood tested frequently as long as they take the drug [97-
99].
Drug Errors
a
Drug errors are mistakes made by doctors, health care practitioners, pharmacists, and
patients when drugs are prescribed, given, taken, or stored. Drug errors can make people ill or
allow diseases to worsen or even losses their life. Drug mistakes may be caused by the
ov
following:
 People become confused and take drugs incorrectly.

 Doctors choose the wrong drug or write a prescription for the wrong dose.
N
 Pharmacists incorrectly read the prescription and give the wrong drug or dose.
 Health professionals incorrectly read the label of the drug container and give the
wrong drug or dose.
Drug Overview 35
 The pharmacist or person incorrectly stores the drug, weakening the drug's strength.
 People use an expired drug.
People should be sure they understand how and when to take a drug when they pick up a
prescription. People should keep a written list of all their current drugs and dosages and bring
c.
the list to every health care appointment or emergency department visit. If there is any doubt
as to which drugs are being used, people are instructed to bring all their drugs to their health
care appointments for review [100-103].
In
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In: Commonly Used Drugs ISBN: 978-1-63463-828-9

Editor: Rafik Karaman © 2015 Nova Science Publishers, Inc.

Keywords: Drugs, Disease, Drug classification, Drug administration, OTC drugs,

ADHD Attention Deficit Hyperactivity Disorder

API Active Pharmaceutical Ingredients

TNF Tumor Necrosis Factor

health resulting from a disturbance in the structure or function of the body.

Diseases may be classified into the following major categories:

 Infectious diseases: also known as transmissible or communicable diseases. They are

infectious pathogen. A communicable disease that passes through sexual contact is

called a sexually transmitted disease. Antibiotics, antivirals, antifungals,

organ of the body, excluding infections and mental disorders).

chronic illness, and disability in many countries.

Drug can be classified by the following ways:

effects. Drugs are classified by a specific biochemical interaction through which a

systems, (ii) other components of plasmatic membranes, (iii) intracellularly, (iv) a

Class I: high permeability, high solubility; a drug substance is considered ―highly

abacavir, acetaminophen, acyclovir, allopurinol, atenolol, captopril, codeine phosphate,

hydrochlorothiazide, furosemide, ritonavir, acetazolamide and etc.

7. By its source or origin; drugs can be classified according to their origin:

termed enteral or enteric administration (meaning 'through the intestines'). Usually

ibuprofen during the last three months of pregnancy.

or embryocidal or other) and there are no controlled studies in women, or studies in

Table 1. Classification of some drugs [19]

As mentioned previously, drugs can be classified according to various criteria including

may divide drugs into the following main groups [20]:

Anticoagulants: prevent or delay blood clotting such as heparin, warfarin, dabigatran,

Antidiabetics: used to manage diabetes.

opioids, flumazenil: antidote of benzodiazepines, N-Acetyl cysteine: antidote of paracetamol,

Antidysrhythmics: control and prevent cardiac dysrhythmias

Examples include busulfan and cyclophosphamide.

aripiprazole, clozapine, olanzapine, quetiapine, risperidone, sertindole, chlorpromazine,

trifluoperazine and zuclopenthixol.

Antispasmodics: control hyper motility in IBS. Examples include anisotropine, atropine,

areas affected by inflammation. Examples include rofecoxib and celecoxib.

such as acetazolamide and methazolamide, potassium-sparing diuretics such as

atorvastatin, fluvastatin, lovastatin, pitavastatin, pravastatin, rosuvastatin and simvastatin,

(ezetimibe) and omega-3- fatty acids.

metaxalone, orphenadrine, chlorzoxazone and methocarbamol,

Ophthalmic anti-infective agents: treat eye infections. Examples include levofloxacin,

Dispensing of medication is often regulated by governments into three categories:

Over-the-counter (OTC): medications which are available in pharmacies and

The regulatory process known as Rx-to-OTC switch is allowing Americans to take a

Figure 1. Chemical structures of acetaminophen, aspirin, naproxen and ibuprofen.

Figure 2. Chemical structures of guaifenesin, dextromethorphan and pseudoephedrine.

Figure 3. Chemical structures of chlorpheniramine and cetirizine.

Figure 4. Chemical structures of ranitidine, benzocaine and miconazole.

difficult to administer than a subcutaneous or intramuscular injection because inserting a

Lysergic acid diethylamide Tianeptine

Figure 5. Chemical structures of lysergic acid diethylamide, tianeptine and amphetamine.

(Figure 5), valproate and isoflavones [26-35].

effectiveness of a medicine or possibly increase the action of a particular medicine or produce

of drugs administered to a patient at the same time.

Figure 6. Chemical structures of thiopentone and suxamethonium.

Drug interactions may be due to various processes such as alterations in the

Types of Drug Interactions

Figure 10. Chemical structures of probenecid and methotrexate.

muscle) by adrenaline. Pharmacological antagonism; when a drug antagonizes the effect of

Figure 12. Chemical structures of atropine and acetylcholine.