Pediatric case report of quetiapine overdose and QTc prolongation

Consideration of the risk of QTc interval prolongation associated with atypical antipsychotic administration is mounting, as this can lead to sudden cardiac death.

This is a case report of a 14-year-old boy with a history of major depressive disorder with psychotic features, post-traumatic stress disorder, oppositional defiant disorder, and polysubstance abuse who ingested 1900 mg of quetiapine.

One and one half hours after ingestion, the QTc interval lengthened from 453 msec to 618 msec on the printout (manual calculation was 444 msec to 500 msec, respectively). On the baseline EKG, the QTc interval was 411 msec (manual calculation of 416 msec).

This report presents an association between higher doses of quetiapine, resulting in higher serum levels and QTc interval prolongation. Also, this report demonstrates the importance of manually calculating the QTc interval to ensure accuracy of the measurement. A review of the literature revealed two case reports and a study where quetiapine was associated with an increase in QTc interval. Further studies are necessary to understand the relationship between higher doses of quetiapine, resulting in higher serum levels, and the propensity for QTc interval prolongation to ensure safe clinical use of this medication.