Verapamil toxicity: an unusual case report and review of the literature

Verapamil blocks the rapid influx of calcium into the cardiac myocytes of the cardiac conduction system and smooth muscle of the vasculature, resulting in decreased myocardial contractility, prolonged conduction time, and vascular relaxation. A sustained-release form, verapamil SR (or ER), is available that contains higher levels of medication and requires only once-daily dosing. The majority of reported fatal cases of verapamil toxicity are due to massive, intentional overdoses. Herein, we present an unusual case of fatal verapamil SR toxicity in a 57-year-old female that resulted from accidental overdose of only 3 tablets (720 mg), as witnessed by the decedent's daughter. In spite of the low dose ingested, the postmortem cardiac blood verapamil level was clearly toxic (6000 ng/mL, or 6 mg/L). Her preexisting medical conditions included hypercholesterolemia, hypertension, iron deficiency anemia, diabetes mellitus, and associated mild chronic renal failure. Complicating factors, which likely include the decedent's preexisting renal and cardiac disease, and a review of the available literature will be discussed.