Cimetidine-related cardiac conduction disturbances and confusion.

A 70-year-old woman free of renal or hepatic dysfunction developed reversible mental confusion, sinus bradycardia, and extreme QT interval prolongation following initiation of intravenous cimetidine 1200 mg daily. The association of mental confusion with cardiac conduction impairment in a single patient in the context of cimetidine toxicity is highly unusual. We review this and other reports on potentially fatal cimetidine-related cardiac conduction disturbances to suggest that in patients at risk, in addition to reducing cimetidine dosage, electrocardiogram (ECG) follow-up is indicated to identify dangerous bradycardia and QT interval prolongation.