Olanzapine versus lithium in the maintenance treatment of bipolar disorder: a 12-month, randomized, double-blind, controlled clinical trial.

Objective: The authors compared the efficacy of olanzapine and lithium in the prevention of mood episode relapse/recurrence.

Method: Patients with a diagnosis of bipolar disorder (manic/mixed), a history of two or more manic or mixed episodes within 6 years, and a Young Mania Rating Scale total score > or =20 entered the study and received open-label co-treatment with olanzapine and lithium for 6-12 weeks. Those meeting symptomatic remission criteria (Young Mania Rating Scale score < or =12; 21-item Hamilton depression scale score < or =8) were randomly assigned to 52 weeks of double-blind monotherapy with olanzapine, 5-20 mg/day (N=217), or lithium (target blood level: 0.6-1.2 meq/liter) (N=214).

Results: Symptomatic relapse/recurrence (score > or =15 on either the Young Mania Rating Scale or Hamilton depression scale) occurred in 30.0% of olanzapine-treated and 38.8% of lithium-treated patients. The noninferiority of olanzapine relative to lithium (primary objective) in preventing relapse/recurrence was met, since the lower limit of the 95% confidence interval on the 8.8% risk difference (-0.1% to 17.8%) exceeded the predefined noninferiority margin (-7.3%). Secondary results showed that compared with lithium, olanzapine had significantly lower risks of manic episode and mixed episode relapse/recurrence. Depression relapse/recurrence occurred in 15.7% of olanzapine-treated and 10.7% of lithium-treated patients. Mean weight gain during open-label co-treatment was 2.7 kg; during double-blind monotherapy, weight gain was significantly greater with olanzapine (1.8 kg) than with lithium (-1.4 kg).

Conclusions: These results suggest that olanzapine was significantly more effective than lithium in preventing manic and mixed episode relapse/recurrence in patients acutely stabilized with olanzapine and lithium co-treatment. Both agents were comparable in preventing depression relapse/recurrence.