PHARMACOLOGY

H2 RECEPTOR ANTAGONISTS ::

James Black and co-workers U.K.made a break through in the history of antisecretory agents by the discovery of H2 receptor antagonists metiamide burimamide and cimetidine Metiamide and burimamide were toxic to be used therapeutically Cimetidine was the first compound to be used in peptic ulcer Recently many more new compounds have been discovered such as famotidine oxmetidine ranitidine tiotidine and SKF 93474 Ranitidine and famotidine have also been the successful drugs Cimetidine has imidazole ring whereas newer agents have either furan (ranitidine) or thiazole (famotidine nizatidine ) 

Mechanism of action ::

Histamine H2 receptor stimulation causes increase in cyclic AMP which inturn stimulates H+ K+ ATPase pump to release gastric acid Recently omeprazole the inhibitor of H+K+ATPase is also used in gastric ulcers