Objective: Quetiapine, combined with lithium or divalproex, demonstrates efficacy in the maintenance treatment of bipolar I disorder. This study investigated the efficacy and safety of quetiapine monotherapy as maintenance treatment in bipolar I disorder compared with switching to placebo or lithium.
Method: Patients aged ≥ 18 years with DSM-IV-diagnosed bipolar I disorder and a current or recent manic, depressive, or mixed episode received open-label quetiapine (300-800 mg/d) for 4-24 weeks. Patients achieving stabilization were randomized to continue quetiapine or to switch to placebo or lithium (0.6-1.2 mEq/L) for up to 104 weeks in a double-blind trial. Outcome measures included times to recurrence of any mood event (primary outcome measure), manic event, or depressive event. Safety assessments included adverse events and laboratory values. The study was terminated early after planned interim analysis provided positive results. The study was conducted between March 2005 and July 2007.
Results: Of 2,438 patients starting open-label quetiapine, 1,226 (50.3%) were randomized to double-blind treatment, including 1,172 (95.6%) in the intent-to-treat population. Time to recurrence of any mood event was significantly longer for quetiapine versus placebo (hazard ratio [HR] = 0.29; 95% CI, 0.23-0.38; P < .0001) and for lithium versus placebo (HR = 0.46; 95% CI, 0.36-0.59; P < .0001). Quetiapine and lithium significantly increased time to recurrence of both manic events (quetiapine: HR = 0.29; 95% CI, 0.21-0.40; P < .0001; lithium: HR = 0.37; 95% CI, 0.27-0.53; P < .0001) and depressive events (quetiapine: HR = 0.30; 95% CI, 0.20-0.44; P < .0001; lithium: HR = 0.59; 95% CI, 0.42-0.84; P < .004) compared with placebo. Overall rates of adverse events were generally similar between treatment groups, and safety findings for quetiapine were consistent with its known profile.
Conclusions: In patients stabilized during acute quetiapine treatment, continuation of quetiapine significantly increased time to recurrence of any mood, manic, or depressive event compared with switching to placebo. Switching to lithium was also more effective than placebo for the prevention of manic and depressive events.
Trial registration: clinicaltrials.gov Identifier: NCT00314184.
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