Why do we need to classify drugs in different ways?

(N/A) The classification of drugs is necessary because different classification systems serve different purposes for various professionals:
$(i)$ On the basis of pharmacological effect: This classification provides doctors with the whole range of drugs available for the treatment of a particular type of problem. Hence,it is very useful to doctors.
$(ii)$ On the basis of drug action: This classification is based on the action of a drug on a particular biochemical process. It helps in understanding how a drug interacts with biological systems.
$(iii)$ On the basis of chemical structure: This classification provides a range of drugs sharing common structural features,which often exhibit similar pharmacological activity.
$(iv)$ On the basis of molecular targets: This classification provides medicinal chemists with drugs having the same mechanism of action on specific molecular targets. Hence,it is the most useful to medicinal chemists.