Clinical pharmacology of etintidine in patients with duodenal ulcer

The gastric antisecretory activity of etintidine, a new histamine H₂-receptor antagonist, was evaluated in 5 patients with quiescent duodenal ulcer disease. Meal-stimulated acid secretion was measured after 100 and 300 mg oral doses of etintidine, 100 and 300 mg oral doses of cimetidine, and placebo. Reductions from placebo in four-hour gastric acid secretion were 49, 65, 80, and 94%, with 100 mg cimetidine, 100 mg etintidine, 300 mg cimetidine, and 300 mg etintidine, respectively. Drug concentrations in plasma were determined by HPLC. The pharmacokinetics of the 2 drugs were similar. We analyzed sigmoid-shaped concentration-response curves to both agents; the concentrations causing 50% inhibition of meal-stimulated gastric acid secretion were 0.44±0.04 and 0.15±0.04 μg/ml for cimetidine and etintidine, respectively. However, characteristics of these curves were such that the potency difference diminished at higher concentrations.