A study was conducted by Walt and colleagues to measure 24-hour intragastric acidity and nocturnal acid secretion in 10 males with duodenal ulcer in four different 24 hour studies.The subjects participants consumed normal meals, had uninterrupted physical activity, and carried on with their customary intake of tobacco.

The participants received treatment with either placebo, cimetidine 200 mg tds and 400 mg at night, or ranitidine 150 mg bd, or 200 mg bd.

• Investigators noted that ranitidine 150 mg bd led to a reduction in mean 24-hour hydrogen ion activity from 41.8 mmol/l to 13.1 mmol/l (-69%, P <0.001)
• It also decreased nocturnal acid output from 6.1 mmol/h to 0.6 mmol/h (-90%, P <0.01)
• The extent of inhibition with ranitidine was significantly greater than that observed with cimetidine (P <0.001 for 24 hours acidity, <0.05 for night time acid output)
• Plasma concentrations of ranitidine were greater than the IC50 for over eight hours following the administration of the 150 mg dose.

Conclusion -

• The findings suggested that ranitidine appears to be over four times as potent as cimetidine on a molar basis for reducing intragastric acidity.
• Increasing the dose of ranitidine from 150 to 200 mg twice daily does not seem to lead to any additional suppression of intragastric acidity or nocturnal acid output.

Source: Walt RP, Male PJ, Rawlings J, et al. Comparison of the effects of ranitidine, cimetidine and placebo on the 24 hour intragastric acidity and nocturnal acid secretion in patients with duodenal ulcer. Gut 1981;22:49-54.