CP-66948 is a histamine H2-receptor antagonist with gastric antisecretory activity and mucosal protective properties. In Vivo: The affinity of CP-66,948 for the guinea pig atria histamine H2-receptor is 15 times greater than that of cimetidine and seven times greater than that of ranitidine. In vivo, the ED₅₀ value for inhibition of gastric acid secretion in pylorus-ligated rats is 2 mg/kg intraduodenally, and in histamine or pentagastrin-stimulated Heidenhain pouch dogs the antisecretory ED₅₀ values are 0.3 mg/kg per os and 1.0 mg/kg per os, respectively. CP-66,948 also inhibits ethanol-induced gastric hemorrhagic lesions in rats following either oral or systemic administration (ED₅₀ values of 12 mg/kg per os and 6 mg/kg subcutaneously)^[1].