A study by Grimley and colleagues sought to compare the inhibitory effects of over the counter doses of famotidine or ranitidine on nocturnal intragastric acidity. This was a placebo-controlled study.

Investigators assessed 12-hr intragastric acidity in 24 healthy individuals who consumed a standard meal at 18:30 h. They were administered either famotidine 10 mg, ranitidine 75 mg or placebo at 19:30 h in a balanced three-period crossover design.

Gastric juice was aspirated half-hourly 0-3 h after the dose, and then hourly till the end of the study. Integrated pH (area under the curve (AUC) of the pH-time curve) was determined for 0-12 h and 9-12 h post-dose periods.

Findings of the study -

• In the 0-12 h period after dosing, with placebo, the mean AUC was 2.12, and increased by 75% to 3.70 with famotidine (P < 0.001) and by 81% to 3.83 with ranitidine (P < 0.001).
• In the 9-12 h period after dosing, with placebo, mean AUC was 2.13, and increased to 4.07 with famotidine (P < 0.001) and to 3.82 with ranitidine (P < 0.001).
• The pH-raising effects of famotidine and ranitidine were not significantly different during both the periods.

To conclude, famotidine and ranitidine, in over-the-counter doses, were found to have a similar effect on post-meal nocturnal intragastric acidity in healthy individuals, which persisted for up to 12 h after dosing.

Source: Grimley CE, Cottrell J, Mann SG, et al. Nocturnal intragastric acidity after over-the-counter doses of famotidine, ranitidine or placebo. Aliment Pharmacol Ther. 1997;11:881-885.