To evaluate the effectiveness of extended-release quetiapine fumarate (quetiapine XR) as once-daily monotherapy for bipolar depression.

Patients in this double-blind, placebo-controlled study were acutely depressed adults with bipolar I or II disorder (with or without rapid cycling), and were randomized to 8 weeks of once-daily treatment with quetiapine XR 300 mg (n=133) or placebo (n=137). The primary outcome measure was change from baseline to endpoint (Week 8) in Montgomery-Åsberg Depression Rating Scale (MADRS) total score. Secondary outcome measures included response (MADRS total score reduction ≥50%) and remission (MADRS total score ≤12) rates at endpoint, changes from baseline to endpoint in MADRS item scores, and Clinical Global Impressions-Bipolar (CGI-BP) severity of illness and change. Change from baseline was compared between groups with analysis of covariance using last observation carried forward approach.

Quetiapine XR 300 mg/d was significantly more effective than placebo in improving depressive symptoms, from first assessment (Week 1; P< 0.001) to endpoint (P< 0.001). Compared with placebo, quetiapine XR was associated with higher response (P< 0.001) and remission (P< 0.05) rates and greater improvements from baseline to endpoint in MADRS total score (-17.43 vs -11.92; P< 0.001), MADRS item scores for core symptoms of depression, and CGI-BP-related outcomes at Week 8. Most common adverse events with quetiapine XR were dry mouth, somnolence, and sedation.

Quetiapine XR (300 mg) once-daily monotherapy was efficacious (from Weeks 1 through 8) compared with placebo and generally well tolerated in bipolar depression.

Supported by funding from AstraZeneca Pharmaceuticals LP.