The effect of ranitidine and cimetidine on the twenty-four hour intragastric acidity profile and nocturnal acid secretion in duodenal ulcer patients.

Ten duodenal ulcer patients were studied during four 36 h periods, receiving either ranitidine 150 mg twice daily, or ranitidine 200 mg twice daily, or cimetidine 200 mg t.d.s. and 400 mg at night, or placebo. Conditions during the four experimental days were standard. Mean 24 h intragastric hydrogen ion activity on placebo (41.8 +/- 1.5 mmol 1(-1)) was decreased to 21.6 +/- 1.2 mmol 1(-1) on cimetidine, and to 13.1 +/- 1.0 and 12.1 +/- 1.1 mmol 1(-1) by the two dose levels of ranitidine. Nocturnal acid output was decreased by 70% by cimetidine and by 90 and 89% by the two dose levels of ranitidine. In this test system ranitidine was more than four times as potent as cimetidine. Greater decreases in daytime acidity and nocturnal acid secretion were produced by twice-daily ranitidine than by the standard four daily doses of cimetidine