Scope of Pharmacology
The science of Pharmacology has interfaces with Anatomy and Physiology, Organic and Inorganic Chemistry, Microbiology and Pathophysiology. Pharmacology is related to action and uses of drugs. In development of new drugs, pharmacology has greatest contribution. It has two main components: pharmacodynamics and pharmacokinetics. Pharmacodynamics deals with what drug does to the human/animal body. It involves study of action of drugs on receptors, its mechanism of action, indications for clinical use, contra-indications and adverse reactions caused by drugs. Pharmacokinetics deals with what body does towards drugs. It has four main components: Absorption, Distribution, Metabolism and Excretion (ADME). Out of these four components, absorption, distribution and excretion are dependent on transport through membranes without any chemical change in the entity. In metabolism, there is chemical change in the moiety because of action of enzymes in the body. Cytochromal enzymes in the liver are the main metabolising enzymes in the liver. A drug may have n number of metabolites. Every metabolite can have different action in the body. Thus, what we observe as action(s) of drugs is the net effect of main drug moiety and its metabolites. Several factors can alter ADME of drugs. It is the main reason why we get different kinds of actions for the same drug in different individuals.
Clinical pharmacology and therapeutics primarily deals with actions of drug in human beings. It incorporates indications, therapeutic uses, contra-indications, posology, bioavailability, prescription writing and drug nomenclature. The science of clinical toxicology is an extension of clinical pharmacology. Forensic toxicology addresses to medico-legal aspects of use of drugs. Pharmacovigilance is gaining vital importance in last few decades. It involves study of adverse reactions of drugs and their safety. Based on observations on pharmacovigilance, some drugs have been withdrawn from the market due to severe adverse reactions.