Inhibition of gastric emptying and secretion by pirenzepine and atropine in rats.

The effects of pirenzepine and atropine on gastric emptying, gastric secretion and heart rate were studied in rats. Both drugs inhibited gastric emptying and secretion dose dependently and increased pulse rate. In the gastric secretory studies both compounds displayed potencies which were not very dissimilar (ID50 were 8.1 mumol X kg-1 and 1.4 mumol X kg-1 for pirenzepine and atropine respectively, potency ratio 6); pirenzepine was however decidedly less potent than atropine in inhibiting gastric emptying (potency ratio 36 on a molar basis) and in increasing heart rate (potency ratio 125). These data, in accordance with results of clinical trials, indicate that pirenzepine-unlike atropine-can inhibit acid secretion without appreciably affecting gastric motility and cardiac function