Efficacy of the class III antiarrhythmic agent azimilide in rodent models of ventricular arrhythmia.

Azimilide exhibited antiarrhythmic activity in several rodent models of ventricular arrhythmias. In the mouse chloroform model, azimilide provided limited efficacy by the i.p. route (50% at 100 mg/kg versus 20% by vehicle), and no efficacy by the oral route (300 mg/kg). In a rat model in which arrhythmias are induced by ligation and reperfusion of the left descending coronary artery (CALR model), azimilide provided dose-dependent (1-18 mg/kg) efficacy by the intravenous route. The estimated dose that suppressed ventricular fibrillation (VF) was 5.0 mg/kg i.v. At 18 mg/kg i.v. azimilide also partially suppressed ventricular tachyarrhythmia (VT) and extrasystoles (VES). Rats dosed orally (100 mg/kg) were fully protected from VF. In isolated guinea pig hearts exposed to 1 microM ouabain, azimilide at 10 microM prevented the VT and VF seen in 69% and 23%, respectively, of control hearts. In anesthetized guinea pigs, azimilide at 10 and 30 mg/kg i.v. increased the dose of ouabain required to induce VES. While sematilide, dofetilide, and E-4031 significantly increased sensitivity to the arrhythmogenic actions of ouabain (by lowering the dose that caused VF), azimilide did not. Azimilide's antiarrhythmic profile in these rodent models differs from that of other class III agents, since azimilide had less efficacy in the mouse chloroform model, could suppress VT and VES as well as VF in the CALR rat model, and protected from or did not aggravate cardiac glycoside-induced arrhythmias in guinea pigs. These results demonstrating the antiarrhythmic efficacy of azimilide in the intact animal suggest that the compound has a different profile than other class III agents.