Comparison of the inhibitory effect of three antimuscarinic drugs: pirenzepine, atropine and propantheline on acid secretion and gastric emptying in the conscious rat

The present investigation was carried out to compare the effects of pirenzepine, a novel antimuscarinic drug, with those elicited by atropine and propantheline on gastric acid secretion and gastric emptying in the conscious rat. The administration of all three drugs resulted in a dose-related inhibition on both parameters that at large doses was nearly total. Comparison of the ID50 ratios for each antagonist on gastric emptying versus acid secretion showed that pirenzepine was unique in that it selectively inhibited acid secretion. Its potency on acid secretion was about 15 times higher than that elicited on gastric emptying. The results are compatible with the proposed existence of two different classes of gastric muscarinic receptors mediating secretory and motor activities.