Antipsychotic drugs cause bradycardia in GD 13 rat embryos in vitro

► Effects of antipsychotic drugs on heart function were examined on gestational day 13 rat embryos in vitro. ► All tested antipsychotic drugs caused bradycardia. ► Safety margins were much lower for haloperidol and quentiapine than for the other 6 drugs tested. This study investigated the effects of antipsychotic drugs on heart function of gestational day (GD) 13 rat embryos in vitro since they all block the IKr/hERG potassium ion channel in addition to their main pharmacological effect on neurotransmitters. The results showed that all the tested antipsychotic drugs caused bradycardia of the rat embryonic heart in a concentration-dependent manner. However, with the possible exception of haloperidol the tested drugs did not cause arrhythmias typically seen with the highly selective IKr/hERG blocking drug dofetilide. For six of the eight drugs tested the effects on the embryonic rat heart were only seen at free drug concentrations that were much greater than those likely to occur in pregnant women taking antipsychotic medication. However, the safety margins for haloperidol and quetiapine were lower.