A randomized, double-blind, placebo-controlled, two-way crossover study was conducted to evaluate the effect of ranitidine 150 mg four times a day on 24-hr integrated intragastric acidity and 24-hr integrated plasma gastrin concentration.

Both the parameters were measured twice in 23 healthy men on the seventh day of oral dosing with placebo or ranitidine.

• The mean integrated 24-hr intragastric acidity decreased to 32% of the placebo value with ranitidine 150 mg four times daily (placebo 825 mmol/hr/liter, ranitidine 265; Table).
• The mean integrated 24-hr plasma gastrin concentration showed an increase of 122% with ranitidine in comparison with placebo (904 pmol/hr/liter vs. 410 with placebo; Table).
• The median number of hours with pH>3 was 5 hr with placebo and 11 hr during dosing with ranitidine.

Ranitidine 150 mg four times a day led to a significant reduction in mean integrated intragastric acidity for all meal-related intervals as well as during the night.

Table. Mean intragastric acidity and plasma gastrin concentration in ranitidine and placebo groups

Source: Fraser AG, Sawyerr AM, Hudson M, et al. Effects of ranitidine 150 mg four times a day on 24-hour intragastric acidity and 24-hour plasma gastrin concentration. Dig Dis Sci. 1994 Jan;39(1):91-6.