Background Several psychotropic drugs are associated with the prolonged corrected QT interval (QTc) as measured on the electrocardiogram (ECG) that can lead to Torsades de Pointes (TdP) and sudden cardiac death. However, only few studies have evaluated the relationship between prolonged QTc intervals and administration of psychotropic drugs in children and adolescents. Therefore, the objectives of this study were to study the frequency of prolonged QTc intervals and to assess whether there exists a relationship between prolonged QTc intervals and the dose of antipsychotic drugs administered to adolescent psychiatric inpatients.

Methods The study subjects comprised 59 children and adolescents (15 male, 44 female) who were inpatients diagnosed as having F2 according to ICD-10 Classification of Mental and Behavioural Disorders at admission between April 2012 and March 2013. The average age of the subjects was 15.2 ± 2.0 years (range: 10.5–18.5 years). We retrospectively reviewed their medical records to characterise patient demographics, medication received, and QTc intervals on the ECG.

Results The average QTc interval recorded was 434.5 ± 20.3 msec (range: 391–487). The QTc duration was ≥440 msec (range: 442–487) for 21 patients (35.6%). Chlorpromazine equivalents were similar between patients with normal and prolonged QTc values (353.9 ± 301.3 vs. 420.6 ± 348.8; p = 0.47). There were no patients with sudden death or syncope related to TdP.

Conclusions In this study, the frequency of prolonged QTc interval on admission was higher than that previously reported (1.97%), and it did not correlate with the current chlorpromazine equivalents. In the future, we intend to examine the frequency of prolonged QTc intervals among various psychiatric disorders.