A study was designed to determine the effects of ranitidine 150 mg b.d. and 150 mg q.d.s. on intragastric acidity.

Ten patients with past history of duodenal ulcer underwent 24-four-hour intragastric acidity measurement on the fourth day after administration of placebo, and either 150 mg ranitidine b.d. or q.d.s. This was a randomized, double-blind study.

• Twice daily ranitidine reduced median integrated 24-h intragastric acidity by 65.1%, nocturnal acidity by 89.1%, and daytime acidity by 54.6% (all P < 0.01 compared to placebo).
• Ranitidine 4 times a day led to reduction in median integrated 24-h intragastric acidity by 62.3%, nocturnal acidity by 89.9%, and daytime acidity by 48.8%, respectively (all P < 0.01 compared to placebo).
• No significant differences were evident between the two ranitidine regimens (P > 0.05).
• The median length of time for which the pH was >3 was 0 h with placebo, 9.5 h with 150 mg ranitidine b.d., and 9.0 h with 150 mg ranitidine q.d.s.
• The treatment was well tolerated with no drug-related adverse events.

The study revealed that twice daily and four times a day dosage regimens of 150 mg ranitidine lead to considerable suppression of intragastric acidity.

Source: Howden CW, Tsai HH, Reid JL. Twenty-four-hour intragastric acidity in duodenal ulcer patients during dosing with placebo, and 150 mg ranitidine twice or four times daily. Aliment Pharmacol Therap. 1989;3:253-258.