ICI 125,211: A new gastric antisecretory agent acting on histamine H2-receptors

In vitro, ICI 125,211 competitively antagonized the action of dimaprit on guinea pig atrium with an apparent dissociation constant of 1.5 × 10−8M (pA2 = 7.8). In vivo, the histamine dose-response curve in conscious gastric fistula beagles was shifted rightward in parallel without change in the maximal response by intravenous infusions of ICI 125,211 at doses of 0.01 and 0.03 umol/kg/hr (estimated pA2 = 7.3). Our data show that this new drug is at least 10x more potent than cimetidine as an inhibitor of gastric secretion in the dog. ICI 125,211, which is an orally effective antisecretory agent in man and devoid of antiandrogenic activity, is the most potent selective H2-blocker described to date.