Antacids

Antacids are drugs used for the purpose of neutralising or diminishing excessive acidity of the digestive system, or of the different excretions. Substances which act upon the former are termed direct, and upon the latter, remote antacids. Many drugs act in both ways, such as potash, soda, lithia, lime, and magnesia, as well as their combinations with carbonic acid. Some substances—as for instance, ammonia and its carbonate—are only direct antacids, being converted into acids in the body, and thus increasing the acidity of the urine. Others—like the acetates, tartrates, and citrates of the alkalies—are not direct antacids, inasmuch as they are neutral salts, but, being converted into carbonates in their passage through the body, they act as remote antacids, and reduce the acidity of the urine. The direct antacids are required when digestion is followed by the generation of too much acid. When this is confined to the stomach, potash is to be preferred, as being more readily absorbed, or in the case of aged or feeble individuals, ammonia, as being at once a stimulant and an antacid. If the acidity exists in the bowels, soda, lime, or magnesia is to be given, as being less readily absorbed than potash, and more likely therefore to reach the situation of the acidity. The remote antacids are required in all cases where the blood contains uric acid, and the urine is excessively acid. In such cases, potash or lithia must be chosen, as forming much more soluble urates than soda.