The effects of oral cimetidine on food stimulated gastric acid secretion and 24 hour intragastric acidity

Four series of studies were performed to determine the effects of oral cimetidine on gastric function stimulated by food or by normal daily activity. Fifteen healthy subjects and ten patients with duodenal ulceration were investigated: oral cimetidine decreased the gastric acid secretion and/or intragastric acidity of all 25 subjects. Cimetidine 200 mg inhibited the acid secretion in response to a protein meal by a mean of 62%. Studies of 24 hour intragastric acidity demonstrated that when cimetidine is taken as 4 divided doses each day, the exact timing of medication in relation to meals is not critical. However, if the drug is taken after meals higher blood cimetidine concentrations will be present during the inter digestive periods of the day. Doubling the dose of cimetidine from 0.8 to 1.6 g/day (taken in 4 equal doses after meals) resulted in a doubling of peak blood concentrations of the drug, but this was not accompanied by a more marked decrease of intragastric acidity, except during the night. Cimetidine 200 mg 3 times a day after meals, with 400 mg at night will result in the greatest decrease of acidity that can be expected without recourse to much larger doses. Atropine 2.4 mg/day did not enhance the antisecretory effects of cimetidine 1 g/day, nor did it affect the absorption or urinary excretion of the H2 receptor antagonist. Cimetidine is the only antisecretory drug that does not cause acute side effects and this important advantage would be lost if it were given with maximal doses of an anticholinergic. Fasting plasma gastrin concentration and the secretion of gastrin in response to food were unaffected by treatment with cimetidine.