Augmentation of Serotonin Reuptake Inhibitors in Refractory Obsessive-Compulsive Disorder Using Adjunctive Olanzapine: A Placebo-Controlled Trial

Background: The purpose of this study was to explore the efficacy of adding an atypical antipsychotic, olanzapine, to a serotonin reuptake inhibitor (SRI) in treatment-refractory obsessive-compulsive disorder (OCD).

Method: Twenty-six patients aged between 18 and 65 (mean = 41.2, SD = 11.9) years meeting DSM-IV criteria for OCD, who had not responded to SRIs, were treated for 6 weeks in a double-blind, placebo-controlled augmentation study with either olanzapine (up to 20 mg/day) or placebo. Severity of illness was assessed biweekly by the Yale-Brown Obsessive Compulsive Scale (Y-BOCS). Analysis of covariance with baseline Y-BOCS score included as a covariate was used to compare improvement in Y-BOCS scores in the 2 groups. Response was defined as a 25% or greater improvement in Y-BOCS score. Data were collected between April 2001 and May 2003.

Results: Outcome was assessed for all patients using the last observation carried forward. Subjects in the olanzapine group had a mean decrease of 4.2 (SD = 7.9) in Y-BOCS score compared with a mean increase in score of 0.54 (SD = 1.31) for subjects in the placebo group (F = 4.85, df = 2,23; p = .04). Six (46%) of 13 subjects in the olanzapine group showed a 25% or greater improvement in Y-BOCS score compared with none in the placebo group. The final mean dose of olanzapine was 11.2 (SD = 6.5) mg/day. Medication was well tolerated. Only 2 (15%) of 13 subjects who received olanzapine discontinued because of side effects: sedation (N = 1) or weight gain (N = 1).

Conclusion: These results provide preliminary evidence that adding olanzapine to SRIs is potentially efficacious and well tolerated in the short-term treatment of patients with refractory OCD. Controlled studies with larger sample sizes are necessary to more definitively address this treatment strategy.