Prolonged action potential duration of guinea-pig heart muscle after pethidine

Since recent experiments indicated class III antiarrhythmic properties of pethidine in vitro, we studied cardiac effects of pethidine in vivo. Monophasic action potentials at different pacing rates were recorded from the left ventricular epicardium of pentobarbital anaesthetized guinea-pigs by means of suction electrode catheter. Intravenous injection of pethidine 2 mg/kg prolonged the action potential duration, and increased left ventricular developed pressure and dP/dt max, compared to animals receiving saline only. It is concluded that pethidine appears to have class III antiarrhythmic properties.