A substance that neutralizes stomach acid. Antacids come in various forms: Aluminum salts, calcium salts, magnesium salts and sodium bicarbonate. Commonly prescribed aluminum salts include, aluminum carbonate: Basaljel, hydroxide salt: AlternaGEL, combination products (aluminum and magnesium): Gaviscon, Maalox, Mylanta, Di-Gel. Commonly prescribed magnesium salts include, hydroxide salt: magnesium hydroxide (MOM), carbonate salt: Gaviscon (also a combination product) and combination products such as Maalox, Mylanta (aluminum and magnesium)