Garriga M, et al. - This pilot, randomized controlled study aimed to evaluate the efficacy of quetiapine extended release (XR) vs. placebo as a concomitant treatment to mood stabilizers in the control of subthreshold symptoms of bipolar disorder. The researchers concluded that compared to placebo, quetiapine XR 300 mg once daily was significantly more effective in depressive subthreshold symptoms. With the known side effects of quetiapine, adverse events were consistent.

• The researchers performed a pilot phase IIIB, multicentre, prospective, placebo controlled, randomized, double blinded study of 12 weeks follow-up.
• They randomized patients to quetiapine XR 300 mg or placebo once daily.
• The mean change between quetiapine XR and placebo from baseline to study endpoint (week 6) in the Montgomery-Åsberg Depression Rating Scale (MADRS) was the primary outcome.

• Compared with placebo (n=16), quetiapine XR 300 mg (n=16) significantly improved depressive subthreshold symptoms after 6 weeks (P=0.021).
• Between groups, early response (reduction of at least the 20% of the MADRS total score) and remission rate (reduction in MADRS total score <8 and YMRS<8) did not show differences.
• When evaluating subthreshold manic symptoms, quetiapine XR did not show superiority vs placebo, rather it was superior when evaluating functioning (GAF score) in BD type I patients (P=0.005).
• Somnolence (9.1%), increased appetite, dry mouth and dizziness (6.8%) were the most common adverse events.