Cimetidine

WITH the synthesis of burimamide in 1972, Black and his colleagues1 demonstrated the existence of two classes of histamine receptors, H1 and H2. In contrast to the H1 type, H2 receptors are not antagonized by "classic" or conventional antihistamines and are involved in the action of histamine on the gastric parietal cell. Burimamide, the first histamine H2 antagonist, was found to block histamine-stimulated gastric acid secretion selectively but was not active orally. Cimetidine was subsequently synthesized when the second H2-receptor antagonist, metiamide, was found to cause agranulocytosis. The structures of histamine and . . .