Effects of ranitidine and of cimetidine on pentagastrin-stimulated gastric acid secretion.

We compared the effect of oral and intravenous ranitidine, a new H2-receptor antagonist, with that of cimetidine on pentagastrin-stimulated gastric acid secretion in normal subjects. Ranitidine in intravenous doses of 20, 60, and 100 mg and oral doses of 100, 150, and 200 mg inhibited acid secretion. Only the 100 mg iv ranitidine dose was substantially more effective than cimetidine. Comparable dose-related decreases in gastric secretory volume were observed. Acid inhibition correlated strongly (r = 0.90) with plasma ranitidine concentration, with the estimated plasma concentration producing 50% inhibition (IC50) being 95 ng/ml. Maximal acid inhibition achieved was 87.3%. We conclude that ranitidine is a potent inhibitor of gastric acid secretion and should be a valuable addition to the medical treatment of acid-peptic disease.