Anatomical Therapeutic Chemical Classification System
Magnesium carbonate, MgCO3 (archaic name magnesia alba), is an inorganic salt. The most common magnesium carbonate forms are the anhydrous salt called magnesite (MgCO3) and the di, tri, and pentahydrates known as barringtonite (MgCO3·2 H2O), nesquehonite (MgCO3·3 H2O), and lansfordite (MgCO3·5 H2O), respectively. The primary use of magnesium carbonate is the production of magnesium oxide by calcining.
Magnesium hydroxide is practically insoluble in water and solution is not effected until the hydroxide reacts with hydrochloric acid in the stomach to form magnesium chloride. Its neutralising action is almost equal to that of sodium bicarbonate. When the dose is in excess of that required to neutralise the acid the intragastric pH may reach pH 8 or 9. Acid rebound following magnesium hydroxide is clinically insignificant. Magnesium hydroxide has an indirect cathartic effect resulting from water retention in the intestinal lumen.
Magnesium oxide (MgO), or magnesia, is an empirical formula of MgO and consists of a lattice of Mg2+ ions and O2− ions held together by ionic bonding.