Effect of isopropamide on response to oral cimetidine in patients with Zollinger--Ellison syndrome.

Patients with Zollinger-Ellison syndrome whose gastric acid secretion or symptoms were not controlled by cimetidine in conventional dosage were selected for studies of responsiveness of their acid secretion to increasing doses of cimetidine, used either alone or in combination with a long-acting anticholinergic agent, isopropamide iodide. Results indicate that in the group as a whole the suppression achieved with a 900-mg dose of cimetidine was not significantly better than that achieved with a 300-mg dose, although in individual cases this did not hold true. In individuals the combination of cimetidine and isopropamide was generally more effective in suppressing acid secretion than cimetidine alone, used either in the same dose as in the combination or in the next highest possible dosage. This was also true in the group as a whole, where combined therapy showed significant advantage over either drug alone in controlling acid secretion, in the third, fourth, and fifth hours following administration of the drugs. The data suggest that in the minority of patients not controlled by cimetidine 300-600 mg q6h per os, addition of isopropamide (20-40 mg/day) may be preferable to further increasing the dose of cimetidine.