Inhibition of gastric acid secretion by pirenzepine (LS 519) in man.

Pirenzepine is a new tricyclic drug used in the treatment of peptic ulcer disease. The effect of two doses of pirenzepine (25 mg twice daily and 50 mg thrice daily) was examined in ten healthy volunteers during basal acid secretion and under stimulation with two doses of pentagastrin (0.166 microgram/kg . h and 1 microgram/kg.h given as continuous intravenous infusion). Serum drug concentrations were determined by radioimmunoassay, and parallel studies of the salivary function were performed. Pirenzepine, 25 mg twice daily, reduced basal acid output by 50% and 55%, respectively, and inhibited stimulated acid output by 31% and 26%, respectively. The higher dose of pirenzepine, 50 mg thrice daily, augmented the effect insignificantly despite markedly increased serum drug levels. The recommended therapeutic dose of 25 mg twice daily gave no salivary inhibition. Pirenzepine may have an anticholinergic effect on the parietal cell, although systemic side effects were not seen. Pirenzepine does not competitively inhibit pentagastrin-stimulated acid secretion.