Clozapine in Treatment-Resistant Patients With Schizophrenia, Schizoaffective Disorder, or Psychotic Bipolar Disorder: A Naturalistic 48-Month Follow-Up Study

Background: The aim of this study was to evaluate the long-term efficacy and safety of clozapine in patients with treatment-resistant schizophrenia, schizoaffective disorder, or bipolar disorder with psychotic features.

Method: 101 patients with a DSM-III-R diagnosis of schizophrenia (N = 34); schizoaffective disorder, bipolar type (N = 30); or bipolar disorder with psychotic features (N = 37) were naturalistically treated with clozapine at flexible doses over a 48-month period. Data were collected from 1994 to 2000. The Brief Psychiatric Rating Scale (BPRS) and Clinical Global Impressions-Severity of Illness scale total predicted scores over time were estimated with random-effects regression models. Time to response to clozapine, defined as 50% reduction of BPRS score, was analyzed in the 3 diagnostic groups using the Kaplan-Meier method. Survival curves were compared using the log-rank test.

Results: The BPRS total predicted score halved its baseline value in 3 months for bipolar disorder patients, in 6 months for schizoaffective disorder patients, and in 24 months for schizophrenia patients. The proportion of subjects who satisfied the criterion for response to clozapine after 48 months of follow-up was significantly (p < .01) higher in the schizoaffective and bipolar disorder groups (90.0% and 83.8%, respectively) than in the schizophrenia group (64.7%). Baseline scores on the Global Assessment of Functioning (GAF) showed low levels of psychosocial and occupational functioning in all 3 groups. After 48 months of treatment, GAF scores showed a functional improvement in all 3 groups, with significantly (p < .01) greater improvement in the bipolar disorder group compared with the other groups.

Conclusion: The findings of this study confirm the efficacy and safety of clozapine for treatment-resistant patients with a diagnosis of schizophrenia, schizoaffective disorder, or bipolar disorder with psychotic features. Patients with schizoaffective disorder and those with bipolar disorder show greater clinical improvement than those with schizophrenia. Patients with bipolar disorder have the shortest time to response and the highest psychosocial and occupational functioning levels. Patients with schizoaffective disorder have the lowest treatment discontinuation rate.