Over production of acid in the stomach causes irritation and pain. In severe cases, ulcers are developed in the stomach. Until 1970, only treatment for acidity was administration of antacids, such as sodium hydrogencarbonate or a mixture of aluminium and magnesium hydroxide. However, excessive hydrogencarbonate can make the stomach alkaline and trigger the production of even more acid. Metal hydroxides are better alternatives because of being insoluble, these do not increase the pH above neutrality. These treatments control only symptoms, and not the cause. Therefore, with these metal salts, the patients cannot be treated easily. In advanced stages, ulcers become life threatening and its only treatment is removal of the affected part of the stomach.

Which of the following is the least suitable antacid?

Sodium bicarbonate

All can be used as antacids. But when NaHCO₃ (and other hydrogen carbonates) are taken in excess, it increases the alkalinity of the stomach and stimulates the release to more acid to counter it. Metal hydroxides are better as they are insoluble and do not increase the pH above 7.