Effects of 800 mg cimetidine once daily on gastric acid secretion.

Today, the reduction of nocturnal acid secretion is believed to be the most important point in duodenal ulcer therapy. This is supported by the fact that during the day gastric acid secretion is largely buffered by meals. Moreover, independently of food intake the intragastric H+ activity during the day is lower than during the night. During nighttime (2300-0700 h) there was a mean hourly H+ activity of 38 mmol/l--that is, a 65% increase compared with daytime H+ activity with meals--and still a 30% increase without meals. Nocturnal acidity can be suppressed best by single large bedtime doses of H2-receptor antagonists. Cimetidine, 800 mg at night, reduces nocturnal intragastric acidity by 85%; 300 mg ranitidine at night and 40 mg famotidine at night reduce it by 95%. The first clinical trials show that a single nighttime dose of cimetidine or ranitidine is at least as effective in promoting ulcer healing as is twice daily administration.