A Cochrane review [Abstract] 1 included 5 RCTs with a total of 1 165 subjects with bipolar disorder. There was no difference between olanzapine and placebo (either alone or in combination with lithium or valproate) in terms of number of participants who experienced relapse into mood episode (RR 0.68, 95% CI 0.43 to 1.07, 2 studies, n=460). When restricting the analysis to the trial that compared olanzapine monotherapy versus placebo (n=361), there was a difference in favour of olanzapine (RR 0.58, 95% CI 0.49 to 0.69). No difference was found between olanzapine and other mood stabilisers (lithium or valproate) in preventing symptomatic relapse for any mood episode but olanzapine was more effective than lithium in preventing symptomatic manic relapse (RR 0.59, 95% CI 0.39 to 0.89, 1 study, n=361). Olanzapine either alone or as adjunctive treatment to mood stabilisers was associated with significantly greater weight gain than placebo. By contrast, olanzapine was associated with a lower rate of manic worsening, but with a higher rate of weight increase and depression than lithium.
Comment: The quality of evidence is downgraded by indirectness of evidence (differences between the populations) and study quality (high drop-out rate).
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