Electrophysiological Safety of Sertindole in Dogs with Normal and Remodeled Hearts

Abstract

Inhibition of the potassium current I_Kr and QT prolongation are associated with drug-induced torsades de pointes arrhythmias (TdP) and sudden cardiac death. We investigated the cardiac electrophysiological effects of sertindole, an antipsychotic drug reported to prolong the QT interval in schizophrenic patients. In cell cultures, sertindole seemed to be a selective blocker of I_HERG over other ion currents. For I_HERG, the IC₅₀ value was 64 ± 7 nM, whereas _ISCN5A, I_Ca,L, I_Ca,T, I_KCNQ1/KCNE1, and I_Kv4.3 were blocked in the micromolar range. In canine ventricular myocytes, the IC₅₀ value for I_Kr inhibition by sertindole was 107 ± 21 nM. Action potentials in these cells prolonged in a reverse rate- and concentration-dependent manner at 10 to 300 nM sertindole. In vivo, sertindole was administered to anesthetized dogs at clinically relevant (0.05-0.20 mg/kg) and high doses (1.0-2.0 mg/kg) i.v. At 0.05 to 0.20 mg/kg sertindole (plasma concentrations 30-157 nM), QT_c was prolonged by 1 to 5% in normal dogs and by 9 to 20% in dogs with remodeled hearts due to chronic atrioventricular block (CAVB). TdP was not induced at these doses in normal dogs or in CAVB dogs with reproducible induction of TdP by dofetilide in previous experiments. At 1.0 to 2.0 mg/kg sertindole (plasma concentrations 0.5-3.1 μM), QT_c prolonged by 6 to 11% in normal dogs and by 22% in dofetilide-sensitive CAVB dogs. TdP occurred in three of five animals in the latter group. Thus, at high i.v. doses sertindole can pose a serious proarrhythmic risk when electrical remodeling of the ventricles is present. At clinically relevant doses, however, sertindole does not cause TdP in anesthetized dogs with normal or remodeled hearts.