Low doses of clozapine may stabilize treatment-resistant bipolar patients.

Open, uncontrolled studies suggest clozapine can have mood-stabilizing effects in treatment-resistant bipolar disorder. Unfortunately, the side effect profile limits clozapine's use at high doses. We report a series of nine bipolar I disorder patients who improved on relatively low doses of clozapine add-on therapy (250 mg or lower). Retrospectively abstracted clinical data identified nine patients with bipolar I disorder, as defined by DSMIV criteria, treated with low-dose clozapine at inpatient and outpatient settings. Monthly symptom evaluations were collected prospectively using standard assessments. Symptoms of mania and mood lability improved in all patients. Three patients demonstrated striking mood stabilization and returned to previous levels of functioning; five patients evidenced moderate improvement in mood stabilization and functioning; and one patient showed a minimal response. Overall, clozapine did not have a significant antidepressant effect. The mean clozapine dose at the end of the study was 156.3 +/- 77.6 mg/day, and duration of treatment was 12 months. Residual side effects were mild. The symptomatic improvement in these prospectively evaluated patients is consistent with our clinical impression in the majority of patients with bipolar disorder taking clozapine.