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

Histamine H2-receptor antagonists are available over the counter for the treatment of heartburn.

To compare the effects of low doses of ranitidine and famotidine on intragastric acidity in a three-way crossover study.

Healthy subjects (12 male, 12 female) were dosed on three occasions 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) during the day (12.30-22.30 hours) and night (22.30-08.30 hours).

Ranitidine and famotidine were superior (P < 0.05) to placebo in decreasing acidity for daytime and night-time intervals. There were no significant 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 after ranitidine was significantly lower than that after famotidine in the first 2.5-h period following dosing (4.32 mmol/L vs. 9.28 mmol/L; P < 0.05).

Lunchtime doses of ranitidine and famotidine decreased acidity during day- and night-time periods. The effect of ranitidine was significantly greater for the first 2.5 h after dosing.