Effect of low-dose propantheline on food-stimulated gastric acid secretion: comparison with an "optimal effective dose" and interaction with cimetidine.

We evaluated the widely held notion that anticholinergic drugs must be used in near toxic doses to inhibit gastric acid secretion effectively. Nine patients with duodenal ulcer were studied after a low dose (15 mg) and after a near toxic dose (averaging 48 mg) of the anticholinergic, propantheline. Mean (+/- S.E.) inhibition of food-stimulated acid secretion was identical with the two doses of propantheline: 29 +/- 10 and 29 +/- 11 per cent, respectively. In addition, when 15 mg of propantheline was combined with the histamine H2-receptor antagonist, cimetidine, acid secretion was suppressed to a greater degree than with either drug alone. A low dose of propantheline is as effective as a near toxic dose in suppressing food-stimulated acid secretion and augments the inhibitory effect of cimetidine.