Acute
manic episodes in
bipolar disorder require rapid and effective relief.
Bipolar depression is a major component of the
bipolar disorder spectrum. Existing treatment options for
bipolar depression include
lithium,
lamotrigine and conventional
antidepressants. However,
lithium is more effective in treating
mania or
hypomania than depression, both acutely and prophylactically,
lamotrigine has only been demonstrated to be effective in one adequately powered study in acute bipolar I depression, and conventional
antidepressants have been associated with emergent
mania and cycle acceleration. Symptomatic outpatients can expect to spend, on average, 33% of their time in the depressive phase compared with 11% in the manic phase. Consequently, there is a need for additional agents to effectively treat
bipolar depression. The atypical agents
olanzapine,
risperidone and
quetiapine have demonstrated efficacy against the manic phase of
bipolar disorder and appear also to have potential in the depressive phase.
Olanzapine monotherapy significantly improved depressive symptoms compared with placebo in patients with
bipolar disorder in an 8-week randomized, controlled clinical study, but the magnitude of the clinical effect was small. The observed improvement in depressive symptoms became moderately large when
olanzapine was combined with the
antidepressant fluoxetine.
Quetiapine monotherapy also resulted in significant improvements compared with placebo in patients with either bipolar I or bipolar II disorder in another 8-week randomized, controlled clinical study, but the effect size was large. A 6-month open-label study of
risperidone added to ongoing
therapy demonstrated improvements in depressive symptoms in patients with bipolar and
schizoaffective disorders experiencing a manic, hypomanic, mixed or depressive episode. The receptor-binding profile of these agents supports a role in the treatment of depressive symptoms and clinical data are beginning to emerge of their efficacy in both the acute and maintenance setting.