Quetiapine-induced premature ventricular contractions necessitating its discontinuation in a young adult female

To the Editor

Quetiapine, a second-generation an-tipsychotic, is increasingly favoured for both acute and long-term management of psychotic and mood disorders. We describe the case of a young adult female in whom quetiapine had to be discontinued owing to dose-related premature ventricular contractions (PVC).

A 30-year-old woman with paranoid schizophrenia, receiving haloperidol 10 mg/day for the past 3 years, presented with inadequate control of psychotic symptoms. On enquiry, it emerged that she had irregular menstrual cycles with the drug and so did not take the treatment regularly.

Baseline investigations, including electrocardiogram (ECG), were all normal. She was shifted from haloperidol to quetiapine (which usually does not raise serum prolactin) through a cross-taper and lorazepam 4 mg was prescribed nightly to address disturbance of sleep.

When the dose of quetiapine reached 400 mg/day, the ECG showed new onset, uniformly frequent, PVCs. Postural hypotension also developed. There was no breathlessness, palpitation, or other relevant cardiovascular symptoms.

The heart rate (88 per minute) and the QTc interval (450 milliseconds) were normal. An echocardiogram was performed and found normal. A cardiology consultation returned the opinion that there were no structural explanations for the PVCs and that the PVCs were quetiapine-related. When the dose of quetiapine was reduced to 300 mg/day, the PVCs and postural hypotension both decreased but did not remit. Because psychotic symptoms were not controlled at this dose, quetiapine was replaced with aripiprazole through cross-taper. Within 3 days of stopping quetiapine, the postural hypotension and PVCs both disappeared.

Lorazepam was not considered in the causation of the PVCs because it was continued at the same dose, all through; in contrast, the PVCs appeared and attenuated with quetiapine in a dose-related fashion. To our knowledge, there have been only two prior cases of quetiapine-related PVCs reported in literature (Deguchi et al., 2012; O’Shea et al., 2003); however, these sufficed to ethically preclude rechallenge with quetiapine. The Naranjo et al. (1981) score, associating quetiapine with PVCs, was 7, indicating a probable causal relationship. We report this case to add to the literature that quetiapine use, especially in higher doses, may rarely be associated with PVCs.