A Double-Blind, Randomized, Placebo-Controlled Trial of Quetiapine Addition in Patients With Obsessive-Compulsive Disorder Refractory to Serotonin Reuptake Inhibitors

Background: Although serotonin reuptake inhibitors (SRIs) are the most effective pharmacologic treatment currently available for patients with obsessive-compulsive disorder (OCD), 40% to 60% of patients do not respond to this treatment. This study was conducted to evaluate the efficacy and tolerability of quetiapine in addition to an SRI for treatment-refractory patients with OCD.

Method: Forty patients (10 men/30 women, mean +/- SD age = 35.2 +/- 12.1 years; range, 18-60 years) with primary OCD according to DSM-IV criteria who were recruited between February 2001 and December 2002 were randomly assigned in an 8-week, double-blind, placebo-controlled trial to receive dosages titrated upward to 300 mg/day of quetiapine (N = 20) or placebo (N = 20) in addition to their SRI treatment. At entry, all patients were unresponsive to courses of treatment with at least 2 different SRIs at a maximum tolerated dose for 8 weeks. During the study, primary efficacy was assessed according to change from baseline on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS). A responder was defined as having a final Clinical Global Impressions-Improvement scale rating of “very much improved” or “much improved” and a decrease of >= 35% in Y-BOCS score.

Results: An intent-to-treat, last-observation-carried-forward analysis demonstrated a mean +/- SD decrease in Y-BOCS score of 9.0 +/- 7.0 (31%) in the quetiapine group and 1.8 +/- 3.4 (7%) in the placebo group (F = 16.99, df = 1,38; p < .001). Eight (40%) of 20 patients in the quetiapine group and 2 (10%) of 20 patients in the placebo group were responders (chi² = 4.8, df = 1, p = .028). The most common side effects in the quetiapine group were somnolence, dry mouth, weight gain, and dizziness.

Conclusion: The results of this study show that quetiapine in addition to an SRI is beneficial for patients with OCD who do not respond to SRI treatment alone.