i) Tranquilizers are chemical substances used to cure mental diseases or disorders and to reduce mental stress. They can act on higher centres of central nervous system and induce sleep to the patients.
e.g. luminal, seconal, valium.
ii) Analgesics are the chemical substances which are used to relieve or abolish pain without causing impairment of consciousness, mental confusion, incoordination or paralysis or some other disturbances of the nervous system.
e.g. Aspirin, Novalgin
iii) Antibiotics are the chemical substances which are produced by microorganisms like bacteria, fungi, molds etc. which can inhibit the growth or even destroy other microorganisms. e.g. Penicillin G, Ampicillin, Amoxycillin.