Prolongation of the heart-rate corrected QT (QTc) interval is an uncommon but clinically relevant concern during antidepressant therapy. This study published in the Pharmacopsychiatry assessed QTc changes in patients with depression treated with escitalopram or venlafaxine, examining relationships with dose and serum concentrations.

A total of 207 patients with depression received escitalopram 10-20 mg/day for 4 weeks. Non-responders were switched to high-dose venlafaxine 150-375 mg/day for an additional 4 weeks. Serum concentrations were measured weekly, and electrocardiograms (ECG) were recorded at baseline, day 28, and day 56. Established risk factors for QTc prolongation were included as covariates.

Escitalopram did not significantly affect QTc intervals. After switching to venlafaxine, mean QTc increased significantly from day 29 to day 56 (p = 0.007), with a more pronounced effect in men (sex interaction p=0.038). QTc prolongation occurred in 5% of patients during escitalopram treatment and 12% during venlafaxine treatment. Twelve patients experienced critical QTc prolongation, all of whom had higher prevalence of known risk factors. No correlation was observed between serum drug concentrations and QTc intervals.

Escitalopram did not significantly alter QTc intervals in this cohort. Venlafaxine was associated with modest but significant QTc prolongation, particularly in men, and critical prolongations occurred in patients with established risk factors.