The effect of single intravenous doses of cimetidine or ranitidine on gastric secretion.

Intravenous cimetidine, 300 mg or 400 mg, or ranitidine, 50 mg, was administered as a single dose to 36 volunteers in a randomized, crossover fashion. Aspirates of gastric juice were obtained after dosing, and the pH, titratable acidity, gastric fluid volume, and gastric acid output were determined from baseline through 71/2 hours for each subject. Each intervention significantly increased pH and suppressed hydrogen ion concentration, gastric fluid volume, and gastric acid output. Both the magnitudes of the changes when compared with baseline and the time of the mean maximum effects were similar in all three drug regimens. The effect of all three interventions on gastric fluid volume and gastric acid output diminished sharply after 6 hours. The data indicate that the gastric secretory response to all three interventions did not differ substantially.