Limited evidence for effectiveness of olanzapine in long term treatment of bipolar disorder

Clinical question: 
How effective is olanzapine, as monotherapy or adjunctive treatment, in preventing manic, depressive and mixed episodes in patients with bipolar disorder?
Bottom line: 
There is some evidence olanzapine may prevent further mood episodes (especially manic relapse) in patients who responded to olanzapine during an index manic or mixed episode and who have not previously had a satisfactory response to lithium or valproate. However, notwithstanding these positive results, the current evidence is stronger for lithium as first-line maintenance treatment of bipolar disorder. Olanzapine either alone or as adjunctive treatment to mood stabilisers was associated with significantly greater weight gain than placebo. Olanzapine was associated with a lower rate of manic worsening, but with a higher rate of weight increase and depression than lithium.
Caveat: 
Results obtained in this review could be biased owing to the very high overall dropout rate, which could undermine the reliability and clinical interpretation of findings. The included studies did not report on all the outcomes that were pre-specified in the protocol of this review. The review contained only 5 randomised controlled trials that investigated the efficacy and acceptability of olanzapine for long term treatment of bipolar disorder, and for most outcomes only 1 or 2 studies contributed data. The small number of participants and events contributing to the assessment of each outcome may affect the robustness of the results.
Context: 
Bipolar disorder is a severe and common mental illness with a lifetime prevalence of 0.5% to 1.5%.ยน Many patients with bipolar disorder require long term treatment to prevent recurrence. Antipsychotic drugs are often used to treat acute manic episodes. It is important to clarify whether olanzapine could have a role in long term prevention of manic and depressive relapses. 1. Kessler RC et al. Psychological Medicine 1997;27:1079-1089.
Review CD#: 
CD004367
PEARLS No: 
154
Date: 
April, 2009
Authored by: 
Brian R McAvoy