Cimetidine-resistant gastric acid secretion in humans.

A 63-year-old white man presented with highly aggressive peptic ulcer disease that was nongastrinoma in cause. Intensive medical therapy, which included intravenous cimetidine, failed to ameliorate the course of the disease. The patient's gastric acid output was entirely uninfluenced by cimetidine administration with demonstrably adequate blood levels of the drug. This is the first reported case of gastric acid secretion resistant to an H-2 receptor antagonist in a clinical, rather than experimental, setting. Other instances of resistance to the acid-reducing properties of this class of drugs may account for some of the treatment failures encountered in clinical trials.