Effects of dantrolene sodium in rodent models of cardiac arrhythmia

Dantrolene sodium has been compared with reference antiarrhythmic agents in rodent models of cardiac arrhythmia. In a coronary-artery-ligation model in rats, dantrolene sodium (3, 10 and 20 mg/kg i.v.) significantly decreased extrasystoles, episodes of ventricular tachyarrhythmia, and frequency, duration, and total episodes of ventricular fibrillation in a dose-dependent manner. In an electrically induced fibrillation model in rats, dantrolene sodium (10 and 20 mg/kg i.v.) significantly raised ventricular fibrillation threshold in a dose- and time-dependent manner. In contrast to its activity in these models, dantrolene sodium was not active in two chemically induced models involving automaticity. Aconitine-induced arrhythmias in rats and mice and ouabain-induced arrhythmias in guinea pigs were not suppressed by i.v. (10 or 20 mg/kg) or i.p. (100-3000 mg/kg) doses of the drug. These results show that the antiarrhythmic potential of dantrolene sodium, predicted by in vitro Class III and Class IV electrophysiological effects, is expressed in whole animal models.