Pharmacology Definition and Scope

Study Notes

Pharmacology studies drugs and their interactions with living systems.
The term originates from Greek: "pharmacon" (drug) and "logos" (study).
A drug is a substance used to diagnose, prevent, or treat diseases.
The World Health Organization (WHO) defines a drug as something used to modify or explore physiological systems or pathological states.

Drugs originate from natural or synthetic sources.
Natural Sources: Plants (e.g., atropine, morphine, quinine), animals (e.g., insulin, heparin), minerals (e.g., magnesium sulfate, iron), microorganisms (e.g., penicillin, tetracycline), and humans (e.g., immunoglobulins, growth hormone).
Synthetic Sources: Most modern drugs are synthesized (e.g., quinolones, omeprazole). Others are obtained from cell cultures or through recombinant DNA technology (e.g., human insulin) or hybridoma technology (e.g., monoclonal antibodies).

Pharmacokinetics studies drug absorption, distribution, metabolism, and excretion (ADME) – essentially, how drugs move within the body.
Drug movement involves crossing biological barriers (intestinal epithelium, cell membranes, renal membranes, capillary barriers).
Biotransport refers to drug movement across barriers.
Transport Mechanisms: Passive diffusion (high to low concentration, no energy required); Carrier-mediated transport (facilitated diffusion – high to low, no energy; active transport – against concentration gradient, energy required); Pinocytosis (cell drinking); Phagocytosis (cell engulfing particles).

Movement of drug molecules from high to low concentration without energy expenditure.

Polar compounds and some drugs use carrier proteins to cross membranes.
Facilitated diffusion is carrier-mediated transport from high to low concentration without energy use. GLUT 4 is an example facilitating glucose transport.

Pinocytosis: Cell engulfs fluid containing drugs (e.g., insulin crossing the blood-brain barrier).
Phagocytosis: Cell engulfs particles (e.g., botulinum toxin poisoning).

The most common, safest, and oldest route.
Advantages: Safest, convenient, economical, self-administrable, non-invasive
Disadvantages: Slower onset, unsuitable for irritants/unpalatable drugs, potential for gastric irritation/vomiting, some drugs are destroyed by gastric juices (e.g., insulin).