Additive effects of ziprasidone and d,l-sotalol on the action potential in rabbit Purkinje fibres and on the hERG potassium current

Introduction: Ziprasidone, an atypical antipsychotic has been shown to be devoid of cardiac adverse effects in spite of its propensity to prolong the QT-interval via a hERG current inhibition. However, the effects of ziprasidone on the action potential (AP) parameters have not been published yet. Moreover, very little information is available concerning pharmacodynamic interactions between ziprasidone and other hERG channel blockers. Thus, we investigated the putative interaction between ziprasidone and d,l-sotalol on the hERG channels at therapeutic concentrations and their consequences on the action potential prolongation. Methods: AP were recorded at 1 and 0.2 Hz. Increasing concentrations of ziprasidone (0.01-10 μmol/L) were successively superfused for 30 min alone or in d,l-sotalol 10 μmol/L pre-treated fibres. Moreover, the effects of ziprasidone, alone or in association with d,l-sotalol, were investigated on the hERG current. Results: Ziprasidone (1-10 μM) induced a concentration and reverse frequency-dependent increase in APD90 (APD90: + 27% and + 36%, respectively at 1 Hz and + 50% and + 70%, respectively at 0.2 Hz) due to a hERG current blockade (IC50: 0.24 μmol/L). A pre-treatment with d,l-sotalol 10 μmol/L led to an increase in APD90 of + 23% at 1 Hz, stable at 66 ± 4 min. In these pre-treated fibres, ziprasidone (1 and 10 μmol/L) induced an additional AP prolongation (APD90: + 16% and + 18%, respectively at 1 Hz) as compared to d,l-sotalol pre-treatment. Moreover, d,l-sotalol did not interact with the pharmacological profile of ziprasidone on the hERG channel. Conclusion: The present study demonstrates that ziprasidone induces an AP prolongation due to its propensity to block the hERG channel. Moreover, ziprasidone and d,l-sotalol, superfused concomitantly exhibit additive effects on the AP duration since they do not interact as competitors for the hERG channel.