Inhibition of basal and stimulated gastric H+ and pepsin secretion in duodenal ulcer patients by metiamide, an H-2 histamine antagonist.

Metiamide was given orally in one dose of 200 mg in 23 sutdies in patients with duodenal ulcer, 4 in the basal state, 11 during histamine infusion, and 8 before insulin hypoglycemia stimulation. In the latter 8 patients insulin was given at another time without metiamide. In 17 studies acid secretion was suppressed by metiamide--up to 75% in the basal state, 53% after histamine, and 80% after insulin. Pepsin secretion was reduced to the same extent as H+ in the histamine studies but not in the basal (57%) or insulin (44%) studies, so that in the latter pepsin/acid ratios were 3-fold greater than in controls. Blood levels of metiamide were measured in 17 studies. In 10 out of 11 who showed inhibition of 40% or more, peak blood levels of metiamide were 0.45 mug/ml to 1.25 mug/ml. In 5 of 6 who did not show inhibition, blood levels were 0.05-0.4 mug/ml; in the sixth it was 0.8 mug/ml. Therefore a critical blood level for suppression of basal or stimulated secretion appears to be approximately 0.45 mug/ml.