Q.With reference to which classification has the statement, “ranitidine is an antacid” been given?

Classification of Drugs

Drugs (chemicals that interact with macromolecular targets to produce a biological response) are classified in several complementary ways:

1. On pharmacological effect — the kind of biological response, e.g. analgesics relieve pain, antipyretics reduce fever. Useful to a physician choosing a treatment.
2. On drug action — the biochemical process a drug blocks, e.g. antihistamines inhibit the action of histamine.
3. On chemical structure — drugs sharing a common skeleton and similar pharmacological activity, e.g. the sulphonamides.
4. On molecular target — the biomolecule (enzyme or receptor) with which the drug interacts; drugs with the same mechanism act on the same target. This classification is the most useful for medicinal chemists.

The same drug can appear under different heads depending on the criterion used, so identifying which criterion is being applied is the key to matching a drug class correctly.

Classification of drugs by pharmacological effect, drug action, chemical structure and molecular target is part of the chemistry-in-everyday-life chapter of NCERT Class 12 Chemistry, and "classification of drugs class 12 chemistry" is a commonly searched revision term. Distinguishing these classification criteria is a recurring important question in NEET and CBSE board chemistry papers.