i) Analgesics – These reduce or abolish pain without causing impairment of consciousness, mental confusion, incoordination or paralysis or some other disturbances of nervous system.
Example
– Aspirin (Non-narcotic)
– Morphine, Heroin, Codeine etc. (Narcotic)
ii) Antibiotics – In low concentrations antibiotics inhibits the growth or destroys microorganisms by intervening in their metabolic processes. These are used as drugs to treat infections because of their low toxicity for humans and animals.
Example
– Pencillin, Ampicillin, Chloramphenicol etc.
iii) Antihistamines – These prevent the interaction of histamine (a potent vasodilator and is responsible for the nasal congestion associated with common cold and allergic response to pollen) with the receptors. Thus, antihistamines prevent nasal congestion associated with common cold and allergic responses.