Antacids

Antacids, drugs that diminish abnormal acidity in the digestive tract or in the various secretions of other organs. Those that unite directly with free acid in the stomach are known as direct antacids. These include ammonium carbonate, magnesia, potassium bicarbonate, limewater, and chalk. So-called remote antacids, such as the acetates, citrates, and tartrates of the alkalies, act by being changed into carbonates, thus increasing the alkalinity of the blood. Some drugs, such as the carbonates or bicarbonates of sodium, potassium, calcium, magnesium, and lithium, act as both direct and remote antacids.