Basically drugs can be classified in a number of ways. For example classification on basis of their chemical structure, classification on the basis of their action etc.

In the above statement, the classification is based on the pharmacological effect of drugs on the human body.

Antacids refer to those class of drugs which relieve the acidity by either reacting with the excess acid in the stomach [eg – magnesium hydroxide] or by preventing the secretion of an excess of acids by the stomach cells [eg – ranitidine].