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Switching Clozapine Responders to Olanzapine

J Clin Psychiatry 2000;61(12):912-915

Background: Clozapine is an atypical antipsychotic indicated for the management of severely ill patients with schizophrenia who have failed to respond adequately to standard drug treatment. The significant risk of agranulocytosis and seizure associated with clozapine has led to the restrictions in its use. Additionally, drug-induced sedation, sialorrhea, enuresis, and weight gain are often cited as problematic consequences of clozapine treatment. Our primary objective was to determine the effectiveness and safety of a method of slow cross-titration from clozapine to olanzapine among patients responsive to clozapine treatment but experiencing medication-induced adverse events.

Method: Changes in symptomatology, mood, subjective response, and safety were examined in 20 outpatients meeting DSM-IV criteria for schizophrenia or schizoaffective disorder who converted from clozapine to olanzapine. Patients were considered clozapine-responsive as evidenced by improved social function and decreased symptoms with clozapine therapy; however, they were interested in alternative pharmacologic treatment because of clozapine-related side effects.

Results: Equivalent efficacy of olanzapine to clozapine was found in 90% of the patients (18/20) in the study group, without rehospitalization or suicidal behavior in any of the patients. Also notable was a reduction in drug-induced side effects and improved subjective response to pharmacotherapy.

Conclusion: The successful conversion from clozapine to olanzapine has the potential to provide great benefits for the patient, including reducing drug-induced side effects while maintaining symptom control. These preliminary results suggest that further research on converting clozapine responders to olanzapine is warranted.