Verapamil reverses calcium cardiotoxicity

High circulating concentrations of calcium are toxic to the heart and may cause cardiac arrhythmias and arrest. To investigate the therapeutic use of calcium antagonists in hypercalcemia, we evaluated the efficacy of verapamil hydrochloride and magnesium chloride in the treatment of experimental calcium-induced cardiac arrest in laboratory rats. Verapamil rapidly reversed the experimental calcium-induced arrest and improved survival (83% survival versus 0% in controls). Magnesium failed to reverse this toxic event. We conclude from these experimental studies that verapamil may be useful in the treatment of hypercalcemic cardiac toxicity.