A study compared the effects of mealtime and bedtime doses of ranitidine on gastric acidity in patients with duodenal ulcers.

In a single-blind fashion, 15 patients in clinical remission were randomly assigned to receive either placebo, ranitidine 300 mg at night or ranitidine 150 mg thrice daily prior to each of the three daily meals.

The study revealed the following:

• Over a 24-hour period, the two active treatments led to significantly greater acid inhibition compared to placebo.
• The once daily regimen appeared to be better than the three times a day regimen of ranitidine for increase rise in pH values (P <0.001) as well as duration of action, expressed as time spent above pH 3 (P <0.05).
• An evaluation of the two parameters during fractioned periods of the circadian cycle revealed that the three divided doses of ranitidine were more effective during daytime (P <0.01) and evening (P <0.001), while the bedtime dose of the drug was superior during the night (P <0.0001).

It was concluded that a three times a day regimen of ranitidine 150 mg yielded a less potent and shorter-lasting antisecretory effect compared to a single bedtime dose of ranitidine 300 mg.

Source: Savarino V, Mela GS, Zentilin P, et al. Mealtime versus nighttime acid inhibition. A clinical pharmacological study with ranitidine. Dig Dis Sci. 1992 Sep;37(9):1368-72.