Olanzapine is significantly more effective than lithium in preventing manic and mixed episode recurrence in patients with Bipolar disorder, according to results of a 1-year clinical trial. The two agents are comparable in preventing recurrence or relapse of depression.

Dr. Mauricio Tohen, of Lilly Research Laboratories, Indianapolis, Indiana, and colleagues compared the efficacy of olanzapine, sold under the trade name Zyprexa, and lithium in patients with a history of at least two manic or mixed episodes within 6 years.

The subjects first received treatment with olanzapine and lithium for 6 to 12 weeks. Patients who went into remission were then randomly assigned to 52 weeks of therapy with olanzapine or lithium alone.

A total of 543 subjects were enrolled. Overall, 431 (79.4 percent) went into remission and were randomly assigned to olanzapine or lithium. The results are published in the American Journal of Psychiatry

Overall, 30.0 percent of olanzapine-treated patient and 38.8 percent of lithium-treated patients experienced a relapse or recurrence following remission of mania or depression.

Patients treated with olanzapine had a significantly lower risk (14.3 percent) of manic episode and mixed episode relapse or recurrence compared with those treated with lithium (28.1 percent).

Depression relapse or recurrence occurred in 15.7 percent and 10.7 percent of olanzapine- and lithium-treated patients, respectively.

The average weight gain during therapy with both drugs was 2.74 kg. About 28 percent of the subjects experienced at least a 7-percent weight change from the start of the study.

Olanzapine-treated patients had a significantly greater average change in weight during compared with the lithium-treated patients (average1.8 kg versus -1.4 kg, respectively).

Both medications were generally well tolerated.

SOURCE: American Journal of Psychiatry, July 2005.