Verapamil intoxication: a literature review of overdoses and discussion of therapeutic options

Abstract

Calcium channel antagonists can be quite toxic. In the management of poisoning, early recognition is critical. Calcium channel antagonists are frequently prescribed, and the potential for serious morbidity and mortality with overdosage is significant. Ingestion of these agents should be suspected in any patient who presents in an overdose situation with unexplained hypotension and conduction abnormalities. The potential for toxicity should be noted in patients with underlying hepatic or renal dysfunction who are receiving therapeutic doses. Because there is no specific antidote, decontamination of the gastrointestinal tract is crucial. Intravenous calcium should be administered to symptomatic patients because it is relatively innocuous and may be beneficial. Volume expansion should be the initial approach to hypotension unrelated to bradycardia. Patients who have had a verapamil overdose should be observed in intensive care units where Swan-Ganz catheterization and ventricular pacing are routinely available. The choice of sympathomimetic agents for treatment remains controversial. According to the published literature, isoproterenol, epinephrine, and norepinephrine may be more effective in improving bradycardia and the resultant hypotension than dopamine. However, none of these agents is universally effective. A more logical approach may be to improve cardiac output with agents like amrinone. Bay K 8644 and 4-aminopyridine show promise as potential antidotes but at present are still experimental.