Introduction
Pharmacology is a key subject in pharmacy and medical sciences. It explains how drugs act on the body and how the body handles drugs. Understanding pharmacology helps healthcare professionals choose the right medicines, prescribe safely and monitor the patient’s response. This chapter provides simple explanations of basic definitions, sources of drug information and the overall scope of pharmacology.
Definitions
Pharmacology
Pharmacology is the science that studies the effects of drugs on living systems. It explains the actions, uses, side effects and behaviour of drugs inside the body.
Drug
According to WHO, a drug is any substance or product used to modify or study physiological systems or pathological states for the benefit of the patient.
Pharmacokinetics
It deals with the movement of a drug inside the body. It includes absorption, distribution, metabolism and excretion (ADME). It explains “what the body does to the drug”.
Pharmacodynamics
It explains the mechanism of action of drugs, their effects and side effects. It relates to “what the drug does to the body”.
Pharmacy
The branch concerned with preparation, formulation, storage and dispensing of medicines.
Therapeutics
The part of medicine that deals with treatment of diseases.
Chemotherapy
Treatment of infections or cancer using chemicals that selectively damage microorganisms or cancer cells.
Toxicology
The science that studies poisons, their detection and treatment of poisoning.
Clinical Pharmacology
Study of drugs in human beings, including safety, efficacy, side effects and clinical trials.
Essential Medicines
Medicines that meet the healthcare needs of most of the population and should be available at all times in proper dosage forms.
Orphan Drugs
Drugs used for diagnosis or treatment of rare diseases where commercial recovery is difficult.
OTC Drugs
Over-the-counter medicines that can be purchased without prescription (e.g., paracetamol, antacids).
Prescription Drugs
Drugs that must be supplied only on a doctor’s prescription (e.g., antibiotics, antipsychotics).
Sources of Drug Information
- Pharmacopoeias: Official books containing approved drugs, tests, purity standards and storage methods. Examples: IP, BP, EP, USP.
- National Formulary: Gives drug use, dose, warnings and precautions.
- Textbooks and Journals: Provide detailed scientific information.
- Electronic Databases: Micromedex, Medline, Cochrane Library.
- Drug Manuals: PDR, AMA drug evaluations.
- Pharmaceutical Companies: Provide information through medical representatives and product literature.
Drug Nomenclature
Each drug generally has three types of names:
1. Chemical Name
Represents the chemical structure. Example: acetylsalicylic acid is the chemical name for aspirin.
2. Non-Proprietary / Generic Name
Assigned by scientific authorities (e.g., WHO-INN system). It is uniform worldwide and used in prescriptions. Example: paracetamol.
3. Proprietary / Brand Name
Assigned by manufacturers. Example: Crocin for paracetamol, Disprin for aspirin.
Sources of Drugs
Natural Sources
- Plants: alkaloids (morphine, atropine), glycosides (digoxin).
- Animals: insulin, heparin.
- Minerals: ferrous sulphate, magnesium sulphate.
- Microorganisms: penicillin, streptomycin.
Semi-Synthetic Drugs
Drugs originally obtained from natural sources but chemically modified. Example: hydromorphone.
Synthetic Drugs
Most modern drugs are fully synthetic, e.g., paracetamol.
Biotechnology Products
Prepared by genetic engineering techniques. Example: recombinant human insulin, hepatitis B vaccine.
Scope of Pharmacology
Pharmacology is linked with anatomy, physiology, pathology, microbiology, chemistry and clinical sciences. Its main scope areas are:
1. Pharmacodynamics
- Study of mechanisms of drug action.
- Receptor interaction and dose-response.
- Therapeutic indications and contraindications.
- Side effects and toxicity.
2. Pharmacokinetics
- Study of ADME (Absorption, Distribution, Metabolism and Excretion).
- Explains drug levels, onset of action and duration.
3. Clinical Pharmacology and Therapeutics
- Drug use in humans.
- Dosage selection and adjustments.
- Drug interactions, adverse effects and monitoring.
4. Toxicology
- Study of poisons and their management.
- Includes clinical and forensic toxicology.
5. Pharmacovigilance
- Monitoring adverse drug reactions (ADR).
- Ensures drug safety after marketing.
- Helps identify unsafe drugs and withdraw them from market.
Detailed Notes:
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