A three-way crossover study by Hamilton and colleagues compared the effects of low doses of ranitidine and famotidine on intragastric acidity.

Twenty four healthy individuals (12 male, 12 female), with no history of peptic disease, were included, and 22 of these completed all three dosing days. They were given the drugs on three occasions as single oral doses of placebo, ranitidine 75 mg, and famotidine 10 mg, an hour after lunch.

The pH of gastric aspirates was then measured for 20 hours. The study revealed the following:

• Ranitidine and famotidine were superior (P < 0.05) to placebo in reducing daytime and night-time acidity.
• No significant differences were evident 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).
• However, intragastric acidity was significantly lower with ranitidine treatment compared to that after famotidine in the first 2.5-h period after dosing (4.32 mmol/L vs. 9.28 mmol/L; P < 0.05).

To conclude, lunchtime doses of ranitidine and famotidine decreased acidity during the day and night-time and the effect of ranitidine was significantly greater for the initial 2.5 h after dosing.

Source: Hamilton MI, Sercombe J, Pounder RE. Control of intragastric acidity with over-the-counter doses of ranitidine or famotidine. Aliment Pharmacol Ther 2001; 15: 1579±1583.