The requirement for the classification of drugs are as follows -

(i) Pharmacological effect of the drug: This classification helps doctors to identify with a whole range of drugs available for a particular disease condition.

(ii) Drug action: Depending upon the action of a particular drug on a specific biological mechanism, this classification is developed.

(iii) Chemical structure of the drug: This classification provides the range of drugs having common structural features anfd hence similar action.

(iv) Molecular targets of the drug: This classification helpps medicinal chemists to understand the drugs having the same mechanism of action on targets. Hence, it is the most useful to medicinal chemists.