General Pharmacology - ENT
General Pharmacology - ENT
General Pharmacology - ENT
Contents
Pharmacology
Pharmacodynamics n Pharmacokinetics
Drug
Pharmacoteraupetics
Clinical pharmacology
Chemotherapy
Drug Nomenclature
Essential Drugs concepts
Pharmacology
Pharmacology is the science of drugs
(Greek: Pharmacon-drug; logosdiscourse in). In a broad sense, it
deals with interaction of exogenously
administered chemical molecules
(drugs) with living systems.
Pharmacotherapeutics
It is the application of pharmacological
information together with knowledge of
the disease for its prevention, mitigation or
cure.
Selection of the most appropriate drug,
dosage and duration of treatment taking
into account the specific features of a
patient are a part of
pharmacotherapeutics.
Clinical pharmacology
It is the scientific study of drugs in man.
It includes pharmacodynamic and
pharmacokinetic investigation in healthy
volunteers and in patients;
evaluation of efficacy and safety of drugs
and comparative trials with other forms of
treatment; surveillance of patterns of drug
use, adverse effects, etc.
Chemotherapy
It is the treatment of systemic
infection/malignancy with specific
drugs that have selective toxicity for
the infecting organism malignant cell
with no/minimal effects on th2 host
cells.
DRUG NOMENCLATURE
A drug generally has three categories of
names:
(a) Chemical name
It describes the substance chemically,
e.g.1-(lsopropylamino)-3-(1naphthyloxy) propan-2 -ol for
propranolol. This is cumbersome and
not suitable for use in prescribing
RO UTES O F D R U G A D MI NISTRATI O N
Most drugs can be administered b y a variety of
routes. The choice of appropriate route in a given
situation depends both on drug as well as patient
related factors. Mostly common sense
considerations,
feasibility and convenience dictate the
route to be used.
1. Physical and chemical properties of the drug
(solid/liquid/ gas; solubility, stability, pH,
irritancy).
SYSTEMIC ROUTES
The drug administered through systemic routes
is intended to be absorbed into the blood stream
and distributed all over, including the site of
action, through circulation (see Fig. 1.1).
1. Oral
Oral ingestion is the oldest and commonest mode
of drug administration. It is safer, more con.
venient, does not need assistance, noninvasive,
often painless, the medicament need not be sterile
and so is cheaper. Both solid dosage forms
(powders, tablets, capsules, spansules, dragees,
moulded tablets, gastrointestinal therapeutic
systems--GITs) and liquid dosage forms (elixirs,
syrups, emulsions, mixtures) can be given orally.
3. Rectal
Certain irritant and unpleasant drugs can be put
into rectum as suppositories or retention enema
for systemic effect. This route can also be used
when the patient is having recurrent vomiting or
is unconscious. However, it is rather inconvenient
and embarrassing; absorption is slower, irregular
and often unpredictable, though diazepam solution
is rapidly and dependably absorbed from
rectum in children. Drug absorbed into external
haemorrhoidal veins (about 50%) bypasses
liver, but not that absorbed into internal haemorrhoidal
veins. Rectal inflammation can result
from irritant drugs. Diazepam, indomethacin paraldehyde, ergotamine and
few other drugs
are some times given rectally.
4. Cutaneous
Highly lipid soluble drugs can be applied over
the skin for slow and prolonged absorption. The
liver is also bypassed. The drug can be
incorporated
in an ointment and applied over specified
area of skin. Absorption of the drug can be
enhanced by rubbing the preparation, by using
an oily base and by an occlusive dressing.
5. Inhalation
Volatile liquids and gases are given by inhalation
for systemic action, e.g. general anaesthetics.
Absorption takes place from the vast surface of
alveoli-action is very rapid. When administration
is discontinued the drug diffuses ba
.
ck and is
rapidly eliminated in expired air. Thus, controlled
administration is possible with moment to
moment adjustment. Irritant vapours (ether) cause
inflammation of respiratory tract and increase
secretion.
6. Nasal
The mucous membrane of the nose can readily
absorb many drugs; digestive juices and liver are
bypassed. However, only certain drugs like
GnRH agonists and desmopressin applied as a
spray or nebulized solution have been used by
this route. This route is being tried for some other
peptide drugs, like insulin.
7. Parenteral
(Par-beyond, enteral-intestinal)
This refers to administration by injection which
takes the drug directly into the tissue fluid or
blood without having to cross the intestinal
mucosa. The limitations of oral administration
are circumvented.
Some
special forms of this route are:
(a) Dermojet In this method needle is not used;
a high velocity jet of drug solution is projected
from a microfine orifice using a gun like
implement.
The solution passes through the superficial
layers and gets deposited in the subcutaneous
tissue. It is essentially painless and suited for
mass inoculations.