A Randomized Trial Comparing Paroxetine and Venlafaxine in the Treatment of Bipolar Depressed Patients Taking Mood Stabilizers

Background: The treatment of depressive episodes occurring in bipolar patients taking mood stabilizers is an understudied area of research with outstanding clinical consequences. This study was aimed to assess and compare the efficacy and safety of 2 different antidepressant drugs, paroxetine and venlafaxine, in this indication.

Method: Sixty DSM-IV bipolar patients, each presenting with a major depressive episode while receiving mood stabilizers, were randomly assigned to either paroxetine (N=30) or venlafaxine (N=30) for 6 weeks in a single-blind manner. They had to score higher than 17 on the 17-item Hamilton Rating Scale for Depression (HAM-D-17) and have their mood stabilizer blood levels within the therapeutic range. Efficacy was measured by the HAM-D. Reports of side effects were collected at each visit; switch to mania or hypomania was specifically assessed by the Young Mania Rating Scale at 5 of 7 visits.

Results: Significant improvements in HAM-D scores were observed in both paroxetine- and venlafaxine-treated patients (Wilcoxon p<.0001). There were no significant differences in either efficacy or safety measures between the 2 drugs. By intention-to-treat analysis, 43% (N=13) of patients taking paroxetine and 48% (N=14) taking venlafaxine were considered to be responders. Only 3% (N=1) of patients switched to hypomania or mania in the paroxetine group, whereas 13% (N=4) switched in the venlafaxine group.

Conclusion: Paroxetine and venlafaxine are both effective and safe in the treatment of depressive breakthrough episodes in bipolar disorder. There was a suggestion of a slightly higher risk for switch to mania or hypomania with venlafaxine.