Cimetidine inhibits caffeine-stimulated gastric acid secretion in man.

In animals, gastric acid secretion stimulated by the methyl xanthine, theophylline, was not inhibited by histamine H2-receptor antagonists. In this study the effect in man of the H2-receptor antagonist, cimetidine, on gastric acid secretion stimulated by the methyl xanthine, caffeine, was examined. Caffeine was given intravenously for 2 hr in a dose of 9 mg per kg-hr to 5 patients with duodenal ulcer and 5 normal subjects. Three hundred milligrams of cimetidine administered orally 30 min before the start of the caffeine infusion completely abolished the acid secretory response in all subjects, decreasing acid secretion to less than basal rates. It is concluded that in man the H2-receptor antagonist, cimetidine, abolished the acid secretory response to the methyl xanthine, caffeine.