Drugs traditionally used to treat gastrointestinal disorders, including peptic ulcer. They neutralise the hydrochloric acid secreted in the stomach's digestive juices and relieve pain and the discomfort of DYSPEPSIA (indigestion). A large number of proprietary preparations are on sale to the public and most contain compounds of aluminium or magnesium or a mixture of the two. Other agents include activated dimethicone – an antifoaming agent aimed at relieving flatulence; alginates, which protect against reflux oesophagitis; and surface anaesthetics. Antacids commonly prescribed by doctors include aluminium hydroxide, magnesium carbonate and magnesium trisilicate. Sodium bicarbonate and calcium and bismuth compounds are also used, although the latter is best avoided as it may cause neurological side-effects. (See DUODENAL ULCER; STOMACH, DISEASES OF.)