Introduction To Pharmacology

Pharmacology Pharmacology is a Greek word derived from ‘Pharmacon’ which means a drug and ‘Logos’ which means science or a study i.e., the science or the study of a drug is called Pharmacology. Pharmacology is the study of the therapeutic value and/or potential toxicity of chemical agents (drugs) on biological systems. In general terms, pharmacology is the science of drug action on biological systems.

What is a drug? A drug may be defined as a therapeutic substance intended to affect the structure or function of the body in order to restore abnormal function to normal. A drug is a chemical substance that affects processes in living organism & used for treatment, prophylaxis (prevention) or diagnosis of the disease.

In the year 1966, WHO has defined drug in a more comprehensive wayDrug is any substance or product that is used or intended to be used to modify or explore physiological systems or pathological states for the benefit of the recipient. ● Drug is called medicine when used in proper dosage form for safe administration. All medicines are drugs but all drugs are not medicines.

A medicine is a chemical preparation, which usually but not necessarily contains one or more drugs, administered with the intention of producing a therapeutic effect.

Essential drug concept • WHO 1977 • Essential drugs are those drugs which satisfy health care needs of the majority of the population, be available at all times in adequate amounts, in appropriate dosage forms and at reasonable cost.

The nature of drugs ● In the great majority of cases, the drug molecule interacts with a specific molecule in the biologic system that plays a regulatory role. This molecule is called a receptor. ● In a very small number of cases, drugs known as chemical antagonists may interact directly with other drugs. ● Few other drugs (e.g. osmotic agents) interact almost exclusively with water molecules.

Pro-drug A chemical substance that is administered as a precursor of a drug and is converted into an active therapeutic agent inside the body. - Levodopa is a prodrug for dopamine: a neuro transmitter, found deficient in parkinsonism. - Phenacetin is converted into paracetamol: an active antipyretic agent.

Over-the-counter (OTC) drugs Prescription drugs

Classification of drug effects Therapeutic effect: Desired effect Side effect: Any effect other than desired onemild, common, and nontoxic reactions. Usually unavoidable. Adverse effect: Side effect that is harmfuladverse reaction is used to describe more severe and life-threatening reactions. ↓ dose or withdrawal of drug. Toxic effect: Adverse effect resulting from high (toxic) dose.

All unintended actions of a drug that result from the lack of specificity of drug action. Aspirin may produce allergic reactions in some asthma patients, but it can also create anaphylaxis which is an immediate and severe allergic reaction that may be lifethreatening.(respiratory distress and circulatory collapse) Idiosyncrasy: - Antimalarial drug primaquine causes hemolysis of 5-10% of black male. - Sulfonamide causes hemolysis in glucose-6-

Pharmacology: Division Two main divisions of pharmacology- Pharmacodynamics & - Pharmacokinetics

Pharmacokinetics What the body does to the drug. Pharmacokinetics is the branch of pharmacology which deals with the movement of the drug in the body once administered i.e., absorption, distribution, metabolism and

Pharmacodynamics What the drug does to the body. Pharmacodynamics is the branch of pharmacology which deals with the actions of the drug in the body i.e., what happens to the symptoms and signs of the disease i.e., whether they improve or deteriorate and whether the drug has produced any additional effects i.e., side/adverse/toxic effects

Pharmacogenetics This is the study of genetic influences on responses to drugs. Originally, pharmacogenetics focused on familial idiosyncratic drug reactions, where affected individuals show an abnormal-usually adverse-response to a class of drug.