This article is only available in the PDF format. Download the PDF to view the article, as well as its associated figures and tables. This is one of a series of articles written by eminent authorities for the purpose of extending information concerning the official medicines. The twenty-four articles in this series have been planned and developed through the cooperation of the U. S. Pharmacopeial Committee of Revision andThe Journal of the American Medical Association.—Ed. Antacids are employed primarily to reduce or neutralize the acidity of the gastric secretion, preferably by local action rather than through systemic alkalinizing effects. Gastric acidity is largely due to excess of free hydrochloric acid, but other fermentative acids may also contribute to its production. The condition may be recognized by an examination of the gastric contents or may be surmised from the symptoms noted by the patient. However, the ordinary test meal does not demonstrate excessive acidity as often as does the fractional test meal after the use of histamine. IMPORTANT FACTS CONCERNING ANTACIDS