Possible Interaction: Caffeine and Cimetidine

“5 It is suggested that cimetidine inhibits the microsomal metabolism of caffeine.”

“ Cimetidine inhibits basal and nocturnal acid secretion and acid secretion stimulated by histamine, pentagastrin, caffeine , insulin, sham feeding, and food.”

“ Cimetidine reduced theophylline plasma clearance by 30 percent, and measurement of urinary metabolites showed that 3-methylxanthine formation was inhibited more strongly than that of the methylated uric acid metabolites.”

“From clinical observations and pharmacokinetic studies it is obvious that even short-term treatment with therapeutic doses of cimetidine inhibits the hepatic elimination of antipyrine, warfarin, diazepam, desmethyldiazepam, chlordiazepoxide, propranolol, labetalol, metoprolol, phenytoin, carbamazepine, chlormethiazole, theophylline and caffeine.”

“ Caffeine induced similar slight increases in blood pressure and pulse rate in smokers and nonsmokers both before and during cimetidine dosing.”

“ Cimetidine decreased the TBC of caffeine by 31% (to 1.73 ± 0.28 ml/kg/min, P < 0.05) and by 42% (to 0.92 ± 0.11 ml/kg/min, P < 0.01) in smokers and nonsmokers.”

“It is concluded that in man the H2-receptor antagonist, cimetidine , abolished the acid secretory response to the methyl xanthine, caffeine.”

“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.”

“ Cimetidine caused a dose-related inhibition of the metabolism of aminopyrine and caffeine but had no effect on the phenacetin breath test.”