In eight healthy male volunteers single oral doses of 5 mg, 25 mg and 100 mg produced dose-related inhibition of basal and pentagastrin-stimulated acid output (M.A.O.) with an estimated ID50 of 40 mg for the latter. In eight subjects with duodenal ulceration single 100 mg and 200 mg doses produced 85% and 97% inhibition of M.A.O. at peak (3 h post-dose) and 20% and 23% inhibition at 24 h, respectively; inhibition of basal acid output was 97% at 3 h and 50% at 24 h with both doses.

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