A Comparative Study between Olanzapine and Risperidone Regarding Drug-Induced Electrocardiographic Changes

Introduction. Among atypical antipsychotics, none has been linked to torsade de pointes. In the present study, the electrocardiographic changes induced by olanzapine have been compared with risperidone. Method and Materials. 268 patients were entered into an open study for random assignment to olanzapine or risperidone. ECG was taken at baseline and at the end of the treatment. The parameters that had been assessed included Q-T interval (corrected = Q-Tc) and other related parameters. Correction of the observed Q-T interval was done according to Frederica’s formula (QTcF). Results. While 14.86% and 25% of the cases in the olanzapine group showed prolongation and shortening of QTcF, respectively, comparable changes in the risperidone group were restricted to its prolongation (32.5%). Comparison of means between baseline QTcF of risperidone group versus its posttreatment measurement showed a significant increment . Also, the quantity of cases with shortening of QTcF in the olanzapine group was significantly more than its opposite . Conclusion. Comparable propensity of olanzapine and risperidone for induction of electrocardiographic changes demands adequate cautiousness by clinicians, particularly with respect to shortening of Q-T interval, which was mainly noticeable in the olanzapine group. 1. Introduction A study comparing the risk of sudden cardiac death of FGAs and SGAs found that patients taking any antipsychotic medication have at least a twofold greater risk for sudden cardiac death compared to patients who are not treated with these medications [1]. Although multiple factors may contribute to this increased risk, perhaps the most reasonable explanation is that antipsychotic medications cause an increase of serious ventricular arrhythmias, likely via potassium channel blockade and prolonged cardiac repolarization [1]. While the relationship between QTc prolongation, sudden cardiac death, arrhythmias, and antipsychotic medications need to be elucidated; these medications do have the potential to prolong the QT interval to varying levels. In a study thioridazine and ziprasidone were associated with the greatest increases in QTc from baseline using Bazett’s formula, while quetiapine, risperidone, olanzapine, and haloperidol caused smaller increases in QTc [2]. Studies have shown that QTc intervals of over 440？ms and especially over 500？msec are associated with an increased risk of sudden death [3, 4]. A number of antipsychotics have been linked to torsade de pointes and sudden death, among them pimozide, sertindole, droperidol, haloperidol, and