The effects of reboxetine and venlafaxine on ECG variables in depressed patients

Abstract

Objective: Antidepressants exert distinct effects on cardiac autonomic nervous system function depending on their receptor profile; thus, different groups of antidepressants are expected to influence cardiac parameters in varying degrees. This study compares the effects of venlafaxine, a serotonin and noradrenaline reuptake inhibitor and reboxetine, a selective noradrenaline reuptake inhibitor, on ECG parameters and vital signs.

Methods: The cardiac parameters and vital signs of 44 depressed patients were evaluated. The initial dose of venlafaxine XR was 75 mg/day and the dose was increased to 150 mg/day at the end of the 2(nd) week. Reboxetine was started at 4 mg/day and increased to 8 mg/day at the end of the 2(nd) week of the study. Electrocardiography (ECG) was performed and the PR, QRS, QT, and QTc intervals were measured both at the beginning and at the end of the trial, as were the vital signs.

Results: The heart rate was significantly increased in the reboxetine group (Wilcoxon z=-3.510, p < 0.001). The ECG parameters did not demonstrate significant differences at the end of the trial in the venlafaxine group, whereas the QT interval was significantly shortened (Wilcoxon z=-2.157, p=0.031) and the QTc interval significantly prolonged (Wilcoxon z=-2.399, p=0.016) in the reboxetine group at the end of the trial. Diastolic blood pressure (supine) was significantly increased at the end of the trial (Wilcoxon z=-2.390, p=0.017) in the venlafaxine group.

Conclusions: Since antidepressants have distinct receptor profiles,they may have varying effects on cardiac parameters. Reboxetine, a selective noradrenergic drug, is more likely to influence cardiac parameters than venlafaxine, a dual acting drug. Different groups of antidepressants, based on their mechanisms, of action should be studied more extensively with regard to their cardiac effects.