Nocturnal gastric acid secretion: its importance in the pathophysiology and rational therapy of duodenal ulcer.

The importance of nocturnal acid secretion has long been acknowledged. The aim of therapy at present is to control acid secretion throughout the entire 24-h period. However, the fact that in DU patients a 400-mg nighttime dose of cimetidine is more effective than a 200-mg one, along with the observation that poorly responsive patients also show little decrease in H+ activity, suggests that a larger single nocturnal dose is an effective primary treatment for DU patients. In studies investigating the effects of different regimens of H2 antagonists on 24-h H+ activity and nocturnal acid secretion in DU patients and healthy volunteers, 400 mg cimetidine twice daily was compared with 800 mg cimetidine at night, 150 mg ranitidine twice daily, 300 mg ranitidine at night, and placebo. In 12 DU patients no significant difference was observed between twice daily or nighttime cimetidine and twice daily or nighttime ranitidine in the reduction of 24-h H+ activity. Cimetidine at night was significantly more effective than the twice daily regimen in reducing nocturnal acid output. Ranitidine, 300 mg at night, decreased nighttime H+ activity more than 800 mg cimetidine at night, although no significant differences in overnight acid output were observed. In another study of four DU patients and four volunteers, 400 mg cimetidine twice daily was compared with 800 or 1200 mg cimetidine at night, 150 mg ranitidine at night, and placebo. All treatments were equally effective at night but had no effect during the day. Hence, early reports seem to confirm that daytime administration of H2 antagonists is unnecessary.