Haloperidol potently blocked HERG channels with an IC50 of approximately 1 microM, binding preferentially to inactivated channels, which may explain its arrhythmogenic side effects.
Haloperidol blocks HERG potassium channels by binding to inactivated channels, providing a mechanistic explanation for its arrhythmogenic side effects such as QT prolongation.
Effect estimate: IC50 ~ 1 microM
The antipsychotic drug haloperidol can induce a marked QT prolongation and polymorphic ventricular arrhythmias. In this study, we expressed several cloned cardiac K+ channels, including the human ether-a-go-go related gene (HERG) channels, in Xenopus oocytes and tested them for their haloperidol sensitivity. 2. Haloperidol had only little effects on the delayed rectifier channels Kv1.1, Kv1.2, Kv1.5 and IsK, the A-type channel Kv1.4 and the inward rectifier channel Kir2.1 (inhibition < 6% at 3 microM haloperidol). 3. In contrast, haloperidol blocked HERG channels potently with an IC50 value of approximately 1 microM. Reduced haloperidol, the primary metabolite of haloperidol, produced a block with an IC50 value of 2.6 microM. 4. Haloperidol block was use- and voltage-dependent, suggesting that it binds preferentially to either open or inactivated HERG channels. As haloperidol increased the degree and rate of HERG inactivation, binding to inactivated HERG channels is suggested. 5. The channel mutant HERG S631A has been shown to exhibit greatly reduced C-type inactivation which occurs only at potentials greater than 0 mV. Haloperidol block of HERG S631A at 0 mV was four fold weaker than for HERG wild-type channels. Haloperidol affinity for HERG S631A was increased four fold at +40 mV compared to 0 mV. 6. In summary, the data suggest that HERG channel blockade is involved in the arrhythmogenic side effects of haloperidol. The mechanism of haloperidol block involves binding to inactivated HERG channels.
Suessbrich et al. (Sat,) reported a other. Haloperidol was evaluated on Inhibition of HERG potassium channels (IC50 ~ 1 microM). Haloperidol potently blocked HERG channels with an IC50 of approximately 1 microM, binding preferentially to inactivated channels, which may explain its arrhythmogenic side effects.