What are the Antacids

Antacids are medicines that counteract (neutralise) the acid in your stomach to relieve indigestion and heartburn.


Antacids are weak bases that are taken orally and partially neutralize gastric acid and reduce pepsin activity.

They are used as symptomatic relief of hyperacidity and should not be used as long-term treatment.

What is a antacid used for?

Antacids are used to neutralize excess stomach acid and relieve symptoms of indigestion, heartburn, and acid reflux.

What are the three main types of antacid preparations?

There are three main types of antacids, those containing calcium, those containing magnesium, and those containing aluminum

Sodium bicarbonate

  • It has rapid onset and short duration.
  • It can be absorbeds ystemically leading to salt & water retention and metabolic alkalosis.
  • It is contraindicated in hypertension and heart failure.

Calcium carbonate

  • Partially absorbed ant-acid.
  • Ca2+ may act directly to stimulate gastrin secre-tion leading to acid rebound.
  • It is contraindicated in hypercalcemia and renal stones.

Magnesium and aluminum salts (Mg hydroxide and Aluminium hydroxide)

  • They are poorly ab-sorbed from GIT and have no systemic effects.
  • The unabsorbed Mg salts cause osmotic di-arrhea the unabsorbed Al salts cause constipation.
  • They have slow onset.

Adverse effects of antacids

Change in bowel habits: Al3+ hydroxide causes constipation, while Mg+2 hydroxide cause diarrhea. For this reason, both salt sare combined together to manage this problem.

Rebound hyperacidity: with Ca+2 and NaHCO3 containing antacids.

Cation overload:

Na salts → hypertension and systemic alkalosis.

Ca salts → hypercalcemia renal stones and milk-alkali syndrome.

Decrease absorption of other drugs: the metal ion in some preparations can chelate other drugs especially tetracycline, digitalis and iron.