The efficacy and selectivity of pirenzepine. Review and commentary

Pirenzepine is a new anticholinergic agent which selectively binds to gastric mucosal muscarinic receptors. We reviewed the double-blind, therapeutic studies on ulcer patients and the clinical pharmacology for evidence of healing and selectivity. Healing rates of ulcer at doses of 100-150 mg/day varied between 54-84% in trials with 718 duodenal ulcer patients and 630 patients with gastric ulcer. Total side effects incidence in these trials was 18.1%. At 150 mg/day, there was 13.5% incidence of dry mouth, 6.3% incidence of visual disturbance and 2.6% incidence of constipation. In clinical pharmacology trials, pirenzepine moderately inhibited gastric secretion with a slight inhibition of salivary secretion and esophageal motility at 100 mg/day. Higher doses produced the expected parasympatholytic profile, except for the absence of cardioacceleration. We conclude that pirenzepine in low doses, compared to classical antimuscarinic drugs, is relatively selective for gastric hyposecretion. It may be associated with a lower frequency of side effects in therapeutic trials at doses of 100-150 mg/day. Dry mouth and visual disturbance are the most common side effects. Selectivity is dose limited and has so far been demonstrated only at a daily dosage of 100 mg, in 2 divided doses.