Chemical substances of natural or synthetic origin which are used for

curing diseases and reducing suffering from pain are called medicines or

drugs. The branch of science which deals with the treatment of diseases

using suitable chemicals is known as chemotherapy.

A medicine is a chemical substance which cure the disease is safe to use

has negligible toxicity and does not cause addiction. In contrast, a drug is

a chemical substance which also cures the diseases but habit forming

causes addiction and serious side effects.

Antacids are drugs which raise the pH to an appropriate level in the

stomach. Some basic compounds like sodium bicarbonate, magnesium

carbonate, aluminium hydroxide and magnesium hydroxide gel act as

antacids by neutralizing hydronium ions in stomach acid.

The drugs cimetidine (Tegamet) and ranitidine (Zantac) act as antacids by

preventing the interaction of histamine with the receptors present in the

stomach wall resulting in release of lesser amount of acid.

Omeprazole and lansoprazole are also marketed as antacids.

The drugs which act on the central nervous systems (CNS) and help in

reducing stress and fatigue by inducing a sense of well being are called

tranquillizers. The most commonly used tranquillizers are barbituric acid

and its 5, 5 – disubstituted derivatives such as veronal, luminal, seconal

amytal and membutal.

Cleordiazepoxide and meprobante are relatively mild tranquillizers and

hence are used for relieving tension. Equanil is used for reducing

depression and hypertension.

Reserpine isolated from the Indian plant Rauwolfia serpentine is also a

powerful tranquillizer. It also slows down the pulse rate and lowers the

blood pressure.