Gastric acid inhibition and oxmetidine kinetics in duodenal ulcer.

Gastric acid inhibitory effects and kinetics of oxmetidine, a new histamine H2-receptor antagonist, were examined in five patients with duodenal ulcer disease. A constant intravenous infusion of impromidine was used to stimulate gastric acid secretion for 6 hr. Oxmetidine was then given in a 28-mg IV infusion and a 200-mg oral solution. The maximum inhibition of gastric acid output was, on average, 77% after infusion and 92% after oral doses, with similar values for volume inhibition. Mean overall percent inhibition of acid output, volume, and H+ concentration was 22%, 8%, and 15% for the intravenous dose and 51%, 33%, and 29% for the oral dose. The effect lasted for 3 hr after the intravenous dose and for 5 hr after the oral dose. Mean values for systemic clearance and half-life were 161 ml/min and 2.3 hr. An average of 4.3% of the dose was recovered in urine as unchanged drug and 27% was recovered as a glucuronide metabolite. Mean bioavailability was 36%. Plasma concentration for 50% inhibition of acid output was 0.50 microgram/ml, indicating that oxmetidine is 2.5 times as potent as cimetidine. No adverse effects were noted during the study.