Strengths:
- Well-documented efficacy in acute mania and maintenance therapy – less so for bipolar depression (OFC).
- Potential antidepressant effect.
- Low EPS risk (compared with conventional antipsychotics, e.g. haloperidol).
Weaknesses:
- Causes weight gain.
- Associated with diabetes and hyperglycemia (class effect).
- Associated with hyperprolactemia (class effect).
- Associated with somnolence and depression (side effect).
Key claims:
Efficacy:
- Reduced relapse rate: significantly reduces rates of manic and depressive relapse
- Increased time to relapse: significantly prolongs the time to relapse into a depressive or manic episode
- At least as effective as lithium: olanzapine is at least as effective as lithium in prolonging remission in bipolar disorder and more effective than lithium in preventing relapse into mania
- OFC in bipolar depression: OFC is more effective than placebo or olanzapine alone in the treatment of bipolar depression and rapid-cycling depression
- No treatment-emergent mania: no risk of treatment-emergent mania with olanzapine or OFC therapy in depressed bipolar patients
- Improvements in HR-QoL: olanzapine and OFC improve HR-QoL in depressed bipolar patients
Tolerability:
- Fewer drop-outs than lithium: more patients remain on olanzapine therapy compared with lithium in the maintenance of bipolar disorder
- No QTc prolongation: olanzapine is not associated with QTc prolongation
General/positioning:
GSK counterclaims:
- Olanzapine has never been studied as a maintenance treatment in patients who were initially depressed at study entry.
- Olanzapine has been shown to be no more effective than lithium in preventing depressive episodes.
- The effect size for olanzapine in the treatment of acute bipolar depression is modest and smaller than that of lamotrigine.
- Both olanzapine and OFC caused significant weight gain after only 8 weeks of treatment.
- Depression and somnolence are consistently among the most frequently side effects observed with olanzapine maintenance treatment.
- Weight gain has been a significant issue in olanzapine treatment observed in every clinical trial presented to date.