Clozapine and the Course of Bipolar Disorder in the Systematic Treatment Enhancement Program for Bipolar Disorder (STEP-BD)

The potential of clozapine in severe bipolar disorder is suggested by its efficacy in refractory schizophrenia, but the evidence is limited thus far. This report utilizes data from the standard care pathway of the Systematic Treatment Enhancement Program to examine the clinical impact of clozapine in bipolar disorder, comparing it to two groups, one that received olanzapine and an additional group that received neither drug.

A total of 4,032 outpatients were available for this analysis. Groups for longitudinal analyses are based on the medication used at each visit. Outcomes assessed were clinical status, symptoms subscales, hospitalizations, and death. We utilized mixed models and generalized estimating equations to adjust for baseline differences and investigate longitudinal differences in symptoms, clinical status, and hospitalization rates between groups.

During the study, 1.1% (n = 43) of the patients used clozapine at any time. Those on clozapine had significantly fewer manic and depressive symptoms during follow-up as compared with those on neither clozapine nor olanzapine, while those on olanzapine had more symptoms. The use of clozapine was not associated with an increased risk of hospitalization. No deaths were recorded for clozapine group during the trial.

Although prescribed to very few patients, the impact of clozapine was notable, with fewer symptoms in patients who had more severe illnesses at baseline. Clozapine could prove to be as successful an intervention for late-stage bipolar disorder as it has been in schizophrenia.