Control of intragastric acidity with over-the-counter doses of ranitidine or famotidine

Background: Histamine H-2-receptor antagonists are available over the count er for the treatment of heartburn. Aim: To compare the effects of low doses of ranitidine and famotidine on in tragastric acidity in a three-way crossover study. Methods: Healthy subjects (12 male, 12 female) were dosed on three occasion s with single oral doses of placebo, ranitidine, 75 mg, and famotidine, 10 mg, 1 h after lunch. The pH of gastric aspirates was then measured for 20 h . Subjects ate standard meals and snacks. Analysis of variance was used to determine the statistical significance of differences in acidity (mmol/L) d uring the day (12.30-22.30 hours) and night (22.30-08.30 hours). Results: Ranitidine and famotidine were superior (P<0.05) to placebo in dec reasing acidity for daytime and night-time intervals. There were no signifi cant differences in mean gastric acidity between ranitidine and famotidine during the daytime (11.37 mmol/L vs. 13.42 mmol/L, respectively) and night- time (23.57 mmol/L vs. 24.74 mmol/L, respectively). Intragastric acidity af ter ranitidine was significantly lower than that after famotidine in the fi rst 2.5-h period following dosing (4.32 mmol/L vs. 9.28 mmol/L; P<0.05). Conclusions: Lunchtime doses of ranitidine and famotidine decreased acidity during day- and night-time periods. The effect of ranitidine was significa ntly greater for the first 2.5 h after dosing.