Risperidone prolongs cardiac action potential through reduction of K+ currents in rabbit myocytes

Prolongation of QT interval by antipsychotic drugs is an unwanted side effect that may lead to ventricular arrhythmias, The antipsychotic agent risperidone has been shown to cause QT prolongation, especially in case of overdosage, We investigated risperidone effects on action potentials recorded from rabbit Purkinje Fibers and ventricular myocardium and on potassium currents recorded from atrial and ventricular rabbit isolated myocytes. The results showed that (1) risperidone (0.1 - 3 muM) exerted potent lengthening effects on action potential duration in both tissues with higher potency in Purkinje fibers and caused the development of early after depolarizations at low stimulation rate; (2) risperidone (0.03-0.3 muM) reduced significantly the current density of the delayed rectifier current and at 30 muM decreased the transient outward and the inward rectifier cut-rents. This study might explain QT prolongation observed in some patients treated with risperidone and gives enlightenment on the risk of cardiac adverse events. (C) 2002 Elsevier Science B.V All rights reserved.