QTc Prolongation during Concurrent Treatment with Depot Antipsychotics and High-dose Amisulpride: A Report of 2 Cases

Antipsychotic drugs may cause prolongation of the heart rate-corrected QT interval (QTc). Amisulpride, a relatively new atypical antipsychotic drug, has been considered to have few cardiac adverse effects, except in cases of overdose. We report 2 schizophrenic patients with no history of cardiac disease who developed significant QTc prolongation after concurrent use of intramuscular depot injections of typical antipsychotics and high-dose amisulpride. A 37 year-old woman, had no known history of arrhythmia. Previous exposure to flupenthixol decanoate had not resulted in cardiotoxicity. She was treated with weekly depot injections of flupenthixol and with amisulpride 1400mg/day, after which QTc prolongation was noted. The electrolytes were normal. The ECG normalized when we switched from amisulpride to another antipsychotic medication. Another patient was a 38 year-old woman who had a cardiac arrest after 7 days of concurrent use of haloperidol decanoate 50 mg and amisulpride 1400mg/day. She was resuscitated but was seen to have QTc prolongation on subsequent ECGs. This abnormality resolved within 3 days after amisulpride was discontinued. In both cases, it was only the simultaneous administration of 2 drugs that was associated with the adverse effect. It is possible that the combination had an additive effect on the human Ether-a-go-go Related Gene (hERG) potassium channel.