Pharmacology is the study of how drugs interact with living systems. It involves understanding the physiological and biochemical effects of drugs, their mechanisms of action, absorption, distribution, metabolism, and excretion. Key terms include drug, chemotherapy, toxicology, and orphan drugs. Essential drugs are those that address priority healthcare needs and are selected based on safety, efficacy, and cost-effectiveness. Drugs can be administered through various local and systemic routes including oral, rectal, intravenous, intramuscular, subcutaneous, intradermal, transdermal, nasal, inhalational, and sublingual.
2. Introduction
• The word “Pharmacology” is derived from two
Greek words
Pharmacon –Drug
Logos – To study
• In a broad sense, it deals with interaction of
exogenously administered molecules(drug) with
living system.
• Oswald schmiedeberg is regarded as father of
pharmacology.
3. Divisions of pharmacology
• What the drug does to the body.
• It includes physiological and biochemical effects of drugs and their
mechanism of action.
• What the body does to the drug
• It includes absorption, distribution, metabolism and excretion of drug.
4. Basic terminologies
• Drug – It is defined as an article intended for use in the diagnosis,
prevention, treatment and cure of the disease in human beings or animals.
• Chemotherapy – It is the treatment of systemic infection with specific
drugs that have selective toxicity for the infecting organism with no or
minimal effects on the host cell.
• Toxicology – It is the study of poisonous effect of drugs and other chemicals
with emphasis on detection, prevention and treatment of poissioning.
• Orphan drugs – These are drugs or biological products for diagnosis and
treatment of rare disease or condition for which there is no reasonable
expectations that cost of developing and marketing drugs will be recovered
from sell of the drug.
5. Essential drugs
• These are the drugs that satisfy the priority healthcare needs of the
population.
• They are selected with due regard to public health relevance,
evidence on safety and efficacy and comparative cost-effectiveness.
• WHO first published its list of essential medicines in 1977.
• India published its first list of essential medicine in 1996.
• It includes a total of 348 medicines.
7. Local Routes
• Local route include topical application on the skin and mucous
membranes as well as routes like intra articular(Hydrocortisone) and
intrathecal(Amphotericin –B).
• Absorption of a drug from topical route depends upon thickness of
skin.
• It is generally inversely proportional to the thickness.
8. Systemic Routes
• It is broadly divided into enteral and parenteral routes.
• Enteral routes:
These include oral and rectal routes.
• Oral route is safer and economical but several drugs are not effective
by this route because of high first pass metabolism in the liver and
intestinal wall(e.g. nitrates, lignocaine, propranolol).
• Rectal route avoids first pass metabolism to 50% extent. Diazepam is
given by this route in children for febrile seizures.
9. Parenteral routes:
• These may be injectable or non-injectable.
• Injectable routes include intravenous(25°), intramuscular(90°),
subcutaneous(45°) and intradermal(10-15°).
• Intravenous route has 100% bio-availability and is useful in emergencies.
• Intramuscular injection is given deep into the muscles(e.g. streptomycin).
• Subcutaneous route has advantage of self-administration(e.g. insulin).
• Intradermal route is given at an angle of 10-15°C to skin and a bleb must be
formed(e.g. BCG vaccine).
10. • Non-injectables parenteral route include transdermal, nasal,
inhalational, and sub-lingual route.
• Transdermal route is used only for drugs which are highly lipid soluble
and can be absorbed through intact skin(e.g. nitroglycerine, nicotine,
fentanyl, hyoscine).
• Drugs absorbed by nasal route include nafarelin.
• Sublingual route avoids first pass metabolism, can be used in
emergencies(e.g. nitroglycerine, isosorbide dinitrate, clonidine,
nifedipine).
