Based on preliminary evidence of its usefulness in treatment-resistant depression (TRD), an olanzapine/fluoxetine combination (OFC) was examined in comparison with olanzapine, fluoxetine, and venlafaxine in a TRD population. In this 12-week double-blind study, 483 subjects with unipolar, nonpsychotic TRD, with historic failure on a selective serotonin reuptake inhibitor (SSRI) and prospective failure on open-label venlafaxine, were randomized to an OFC or to an olanzapine, fluoxetine, or venlafaxine monotherapy group. Venlafaxine was continued randomly in the double-blind acute phase to explore the benefits of continuation versus switching therapy. The Montgomery-Asberg Depression Rating Scale (MADRS) total change score at end point was the primary outcome measure. The OFC group had significantly greater improvement in depressive symptoms by week 1 of treatment (MADRS mean change =-7.2, baseline =29.6), in comparison to olanzapine (-4.8, P=.03), fluoxetine (-4.7, P=.03), or venlafaxine (-3.7, P=.002) groups and maintained its statistical separation from all three monotherapy groups through week 6. At end point, the OFC group was significantly different only from the olanzapine group (-14.1 vs. -7.7, P<.001). Analysis of a subgroup of subjects who had an SSRI failure in their current depressive episode (n=334) revealed statistical separation from both olanzapine and fluoxetine (but not venlafaxine) at end point: OFC (-14.6) versus olanzapine (-9.4, P<.001) versus fluoxetine (-10.7, P=.006) versus venlafaxine (-14.7, P=.98). The OFC had a safety profile comparable to its component monotherapies (i.e., olanzapine and fluoxetine), showed a rapid onset of antidepressant effect, and was effective in this TRD sample. At the study end point, OFC, fluoxetine, venlafaxine, and low-dose OFC all appeared to be similarly effective.
