[Effects of ranitidine, a new histamine H2-receptor antagonist, on secretagogue-stimulated gastric secretion in rats: comparison with cimetidine (author's transl)].

Antisecretory effects of ranitidine on secretagogue-stimulated gastric secretion in acute fistula rats were studied. Histamine 2HCl (8 mg/kg/hr), pentagastrin (125 micrograms/kg/hr) or carbachol (128 micrograms/kg/hr) was continuously given i.v. by an infusion pump, through the tail vein to acute fistula rats. Gastric secretion was collected hourly for 5 hr and analyzed for its components. Cimetidine was used as a reference drug. Both drugs were given i.v. by a bolus injection in the tail vein 30 min after the injection of each stimulant. Both ranitidine (1 and 10 mg/kg) and cimetidine (10 and 60 mg/kg) significantly (P less than 0.05) inhibited the histamine-stimulated gastric secretion (volume, acid and pepsin output) for 1 to 4 hr. Both ranitidine (10 mg/kg) and cimetidine (60 mg/kg) significantly (P less than 0.05) inhibited the pentagastrin-stimulated gastric secretion for 2 to 3 hr. both ranitidine (10 mg/kg) and cimetidine (10 and 60 mg/kg) markedly inhibited the gastric acid secretion in response to carbachol. However, cimetidine (10 or 60 mg/kg) significantly (P less than 0.05) stimulated the volume and pepsin output by carbachol. We conclude that ranitidine is about 6 times more potent than cimetidine for histamine- or pentagastrin-stimulated gastric secretion and almost equal to cimetidine for carbachol-stimulated gastric acid output in rats.