The effect of cimetidine on pepsin secretion in patients with Zollinger Ellison syndrome.

Summary We have measured pepsin output in two patients with Zollinger Ellison Syndrome before and after an intravenous dose of cimetidine. Pepsin output increased after H 2 blockade in both patients despite a decrease in both the volume and acidity of secretion. We suggest that nonresponse to cimetidine may be due to increased pepsin secretion when receiving treatment.