Results of the United States ranitidine maintenance trials.

In two long-term studies, efficacy and safety of maintenance therapy with ranitidine (150 mg at bedtime) versus a placebo or cimetidine (400 mg at bedtime) were assessed. Fourteen centers enrolled 125 patients in the ranitidine-cimetidine study, and 26 centers enrolled 277 patients in the ranitidine-placebo study. Both studies were conducted for 12 months. Using life-table analysis, 15 percent of the ranitidine-treated patients and 44 percent of the cimetidine patients relapsed by the 12th month of treatment (p less than 0.007). Ulcer recurrence rates were in 19, 24, and 35 percent for the ranitidine-treated patients and 44, 54, and 60 percent for patients taking placebo at four, eight, and 12 months, respectively (p less than 0.001). Possible reasons for the increased effectiveness of ranitidine over cimetidine are the increased potency of ranitidine and longer acid suppression during the middle and later periods of sleep. No significant changes were observed in multiple laboratory parameters, ophthalmoscopic examinations, electrocardiographic results, or vital signs. All therapies appeared to be safe during this 12-month trial.