KD-Tripathi-Pharmacology-Book-1-99-18-99

  • Chapter 1: General Pharmacological Principles

Introduction to Pharmacology

  • Pharmacology: The science of drugs; studies interactions of exogenously administered chemical substances with living organisms.

  • Early drugs were crude natural products with unknown efficacy and composition.

  • Historical Contributors:

    • Rudolf Buchheim: Founded the first pharmacology institute in 1847.

    • Oswald Schmiedeberg: Known as the ‘father of pharmacology’; established fundamental concepts alongside students like J. Langley and P. Ehrlich.

  • Growth in pharmacology has led to the purification and characterization of drugs leading to the development of highly effective and selective drug therapies.

Divisions of Pharmacology

  1. Pharmacodynamics:

    • What drugs do to the body.

    • Involves physiological and biochemical effects and mechanisms of action (e.g., Adrenaline affects adrenoceptors, increasing intracellular cyclic AMP).

  2. Pharmacokinetics:

    • What the body does to the drug.

    • Involves absorption, distribution, binding, metabolism, and excretion of drugs (e.g., paracetamol absorption and metabolism).

Definitions

  • Drug:

    • A single active chemical entity used in diagnosis, treatment, or prevention of a disease.

  • Pharmacotherapeutics: Application of pharmacological knowledge to the prevention and treatment of diseases.

  • Clinical Pharmacology: Scientific study of drugs in humans, assessing efficacy and safety.

  • Chemotherapy: Treatment of systemic infections/malignancies using drugs with selective toxicity.

  • Pharmacy: Science of compounding and dispensing drugs.

  • Toxicology: Study of the toxic effects of drugs and chemicals.

Drug Nomenclature

  • Drugs typically have three names:

    1. Chemical name: Scientific description (e.g., 1-(Isopropylamino)-3-(1-naphthyloxy)propan-2-ol for propranolol).

    2. Non-proprietary name: Generic name approved by medical authorities (e.g., USAN).

    3. Proprietary name: Brand name given by manufacturers (e.g., Advil for ibuprofen).

Essential Medicines

  • WHO Definition: Essential medicines satisfy priority healthcare needs and are chosen based on efficacy, safety, and cost-effectiveness.

  • They should be available in the right forms and at affordable prices in functioning health systems.

Drug Administration Routes

  • Routes are divided into Local and Systemic action.

Local Routes

  • Topical: Applied externally for localized effects (e.g., ointments, creams).

  • Deeper tissues: E.g., intra-articular injections.

  • Arterial supply: Direct injections (e.g., anticancer drugs).

Systemic Routes

  • Oral: Common, safe, but can have variable absorption.

  • Sublingual/Buccal: Rapid absorption via oral mucosa, avoids first-pass metabolism.

  • Rectal: Useful for patients unable to swallow.

  • Parenteral: Direct injection (IV, IM, SC), useful in emergencies and bypasses digestive tract.

Factors Influencing Route of Administration

  1. Drug properties: Form, stability, solubility.

  2. Desired effect: Local vs. systemic.

  3. Patient condition: Ability to swallow, consciousness.

Pharmacokinetics: Membrane Transport, Absorption, Distribution

  • Pharmacokinetics: Quantitative study of drug movement through the body.

  • Absorption is affected by solubility, pH, presence of food, and route of administration.

  • Distribution depends on lipid solubility, protein binding, and regional blood flow.

Drug Metabolism and Excretion

  • Biotransformation: Chemical alteration to facilitate excretion.

  • Excretion Methods: Mainly through urine, also via feces, lungs, and milk.

  • Affected by kidney function, liver function, and other health conditions.

Conclusion

  • Understanding pharmacology is essential for safe and effective drug use in clinical settings.

  • Future chapters will delve deeper into pharmacodynamics, clinical pharmacology, and drug development.