A study was conducted with eight men who had a history of endoscopically confirmed duodenal ulcers. The subjects were evaluated on two occasions when they were in symptomatic remission - before and on the 7th day of treatment with ranitidine 150 mg at night.

The 24-hour study period was from 22:00 until 21:00 the next day. Gastric juice samples were aspirated every hour and acidity was measured. After the first study period, all patients were given oral ranitidine 150 mg at night for seven days.

• Mean 24-hour intragastric acidity was found to decrease by 42% from 42.9 mmol/l to 24.8 mmol/l.
• Median intragastric pH over 24 hours was shown to increase from pH 1.4 to pH 1.8 during maintenance treatment.
• There were no adverse drug effects.

The study showed that ranitidine 150 mg at night reduced intragastric acidity.

The reduction in nocturnal acidity seen in the study seems sufficient to prevent relapse of ulceration in most patients. 

Source: Santana IA, Sharma BK, Pounder RE, et al. 24 Hour intragastric acidity during maintenance treatment with ranitidine. Br Med J (Clin Res Ed) 1984;289:1420.