Risk of corrected QT interval prolongation in patients receiving antipsychotics

Antipsychotic (AP) use has been associated to QT interval prolongation on the surface electrocardiogram (ECG). Our study aimed to determine the incidence of corrected QT (QTc) interval prolongation among patients admitted to a psychiatric hospitalization unit requiring AP treatment and to assess the relationship between administered dose and QTc interval changes. We enrolled 179 patients admitted to the Hospital Psiquiátrico Departamental Universitario del Valle in Cali, Colombia. ECGs were conducted upon admission, and again at 3 and 7 days postadmission. The QT interval was measured, and QTc interval correction was performed using Bazzet's formula. QTc interval prolongation at time points B or C was observed in 9.5% of patients. Clozapine was the most common AP associated with QTc interval prolongation (20.59%), followed by olanzapine (15.38%). The relative risk of QT interval prolongation with clozapine compared to haloperidol was 4.17 (95% confidence interval, 1.14-15.17, P  = 0.02). AP use upon hospital admission was linked to early (within 3 days) QTc interval prolongation. Clozapine and olanzapine were associated with a greater increase in QTc interval compared to haloperidol, indicating a need for rigorous electrocardiographic monitoring with their use.