Effect of pirenzepine on postoperative gastric secretion

Post surgical stress ulcers of the upper digestive tract, once developed, is difficult to control depending on the primary disease and associated complications. As to the cause of postoperative stress ulcers, decreased defensive factors such as gastric mucosal blood flow and increased gastric secretions have been pointed out. Recently, pirenzepine hydrochloride has been shown to be a specific antagonist of muscarinic cholinergic M1 receptors and a suppressant of gastric acid secretion. Therefore we studied its effect on gastric secretions in postoperative patients. Twenty one patients admitted for abdominal surgery, excluding gastric surgery, were selected and randomly assigned to the pirenzepine group (10 cases) or control group (11 cases). Since the serum half life of pirenzepine is 10 hours, 20mg of pirenzepine was administered intravenously immediately after the operation and twice daily (9 a.m. and 9 p.m.) from postoperative day 1 until day 7. Gastric secretions and gastric pH were measured preoperatively and daily until day 7. In the control group, significant increases in the volume of secretion and significant decreases in gastric pH were observed after the operation. In contrast, the pirenzepine group had a significantly decreased amount of gastric secretion and the gastric pH was higher than those in the control group. Thus we conclude that pirenzepine decreases gastric secretion and increases gastric pH in postoperative patients. Pirenzepine can be regarded as an effective agent for the control of postoperative gastric hypersecretion and possibly a good prophylactic for postoperative stress ulcers.