Long-Term Antidepressant Efficacy and Safety of Olanzapine/Fluoxetine Combination: A 76-Week Open-Label Study

Background: The olanzapine/fluoxetine combination has demonstrated effectiveness in treatment-resistant depression (TRD). Although this combination is being used by prescribers, this is the first study to examine long-term use. Long-term efficacy and safety were therefore investigated in a group of patients with major depressive disorder (MDD) with and without TRD.

Method: 560 patients who met DSM-IV diagnostic criteria for MDD were enrolled in this 76-week, open-label study (Feb. 2000-July 2002). The Montgomery-Åsberg Depression Rating Scale (MADRS) total score was the primary efficacy measure. Safety was assessed via adverse events, vital signs, laboratory analytes, electrocardiography, and extrapyramidal symptom measures.

Results: MADRS mean total scores decreased 7 points from baseline (31.6 [N = 552]) at 1/2 week of treatment, 11 points at 1 week of treatment, and 18 points at 8 weeks of treatment. This effect was maintained to endpoint with a mean decrease of 22 points at 76 weeks. Response and remission rates for the total sample were high (62% and 56%, respectively), and the relapse rate was low (15%). Response, remission, and relapse rates for TRD patients (N = 145) were 53%, 44%, and 25%, respectively. The most frequently reported adverse events were somnolence, weight gain, dry mouth, increased appetite, and headache. At endpoint, there were no clinically meaningful changes in vital signs, laboratory analytes, or electrocardiography. There were no significant increases on any measure of extrapyramidal symptoms.

Conclusions: The olanzapine/fluoxetine combination showed rapid, robust, and sustained improvement in depressive symptoms in patients with MDD, including patients with TRD. The long-term safety profile of the combination was similar to that of its component monotherapies.