Antagonism of vasodepressor and gastric secretory responses to histamine by the H2-receptor antagonists, ranitidine and cimetidine, in the anaesthetized dog.
1 The new H2-receptor antagonist, ranitidine, has been compared with cimetidine as an inhibitor of gastric acid secretion in the anaesthetized dog. 2 Both ranitidine and cimetidine given intravenously inhibited histamine-induced gastric secretion in a dose-related manner. Ranitidine was 4.2 times more potent than cimetidine when given as an intravenous infusion and 9.6 times more potent as an intravenous bolus dose. 3 In a separate series of experiments, ranitidine was compared with cimetidine as an antagonist of vasodepressor responses to histamine. Mepyramine alone displaced the histamine dose-response curve to the right. After a maximally effective dose of mepyramine, further displacement could be achieved with ranitidine and cimetidine, ranitidine being 19.2 times more potent than cimetidine. 4 Ranitidine alone has no effect on vasodepressor response curves to histamine, acetylcholine or (-)-isoprenaline or on vasopressor response curves to phenylephrine. 5 These results indicate that displacement of the histamine dose-response curve after mepyramine blockade by ranitidine and cimetidine is due to selective H2-receptor antagonism.
D000758:Anesthesia; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects*; D002927:Cimetidine / Q000494:pharmacology*; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D005663:Furans / Q000494:pharmacology*; D005744:Gastric Acid / Q000378:metabolism*; D006146:Guanidines / Q000494:pharmacology*; D006632:Histamine / Q000494:pharmacology*; D006635:Histamine H2 Antagonists / Q000494:pharmacology*; D008297:Male; D011738:Pyrilamine / Q000494:pharmacology; D011899:Ranitidine
D005663:Furans; D006146:Guanidines; D006635:Histamine H2 Antagonists; D002927:Cimetidine; D006632:Histamine; D011899:Ranitidine; D011738:Pyrilamine