Drugs have been classified in different ways depending (i) upon their pharmacological effect, (ii) upon their action on a particular biochemical process,(iii) on the basis of their chemical structure and (iv) basis of molecular targets. Each classification has its own usefulness. Classification on the basis of pharmacological effect is useful for doctors because it provides them the whole range of drugs available for the treatment of a particular disease Classification on the basis of action on a particular biochemical process is useful for choosing the correct lead compound for designing the synthesis of a desired drug Classification on the basis of chemical structure helps us to design the synthesis of a number of structurally similar compounds having different substituents and then choosing the drug having least toxicity. Classification on the basis of molecular targets is useful for medicinal chemists so that they can design a drug which is most effective for a particular receptor site
