A Naturalistic Comparison of Clozapine, Risperidone, and Olanzapine in the Treatment of Bipolar Disorder

Background: Our purpose was to evaluate the overall efficacy and tolerability of novel antipsychotic medications for patients with bipolar disorder type I.

Method: A retrospective study of the Massachusetts General Hospital Bipolar Clinic database was carried out to identify 50 consecutive treatment trials in patients with DSM-IV bipolar disorder type I who had received adjunctive treatment with risperidone, olanzapine, or clozapine, along with standard mood stabilizers. The treatment charts of those patients (N = 42) were reviewed for details of adverse effects, tolerability, and efficacy of medication.

Results: Overall results indicated equivalent efficacy in novel antipsychotic treatments according to change in Clinical Global Impressions scale score. Levels of extrapyramidal symptoms were similar in all groups and occurred in 12/42 patients (28.6%). Prolactin-related side effects were not observed in any patients. There were no cases of affective switch or worsening of mania. Substantial weight gain of more than 10 lb (4.5 kg) was significantly greater in patients treated with olanzapine.

Conclusion: These results suggest that the efficacy and tolerability of risperidone, olanzapine, and clozapine are similar in patients with bipolar disorder. One major differentiation factor of these drugs appears to be weight gain, particularly between olanzapine and risperidone. This may, in part, also be related to the need to use mood-stabilizing agents, like lithium or divalproex sodium, which may potentiate the weight-gain effect of novel antipsychotics.

J Clin Psychiatry 2000;61(9):638-642