Why do we need to classify drugs in different ways ?

Explanation

There are a large variety of drugs for different purposes of diagnosis, prevention , relief or cure of different diseases. These have been classified according to various criteria depending upon their pharmacological effect, upon their action on a particular biochemical process on the basis of their chemical structure, on the basis of molecular targets, etc. These classification have their own usefulness. For example,
(i) Classification on the basis of pharmacological effect of the drugs in useful to doctors because it provides them the whole range of drugs available for the treatment of a particular type of disease.
(ii) Classification on the basis of action of a particular biochemical process is useful for selecting the correct lead compound for designing the synthesis of a desired drug.
(iii) Classification on the basis of chemical structure helps to design the drugs having similar pharmacological activity and then selecting the drug with least toxicity.
(iv) 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 acceptor site.