A Preliminary Open-Label Study of Zonisamide Treatment for Bipolar Depression in 10 Patients

Objective: The purpose of this study was to investigate the effectiveness of zonisamide in the treatment of bipolar depression.

Method: Ten patients with DSM-IV bipolar disorder, depressed phase, who had either not tolerated or not responded to previous treatments were given zonisamide in this add-on open-label study. Zonisamide treatment was started at 100 mg/day and increased by 100 mg every 2 weeks to a maximum of 300 mg/day in divided doses (b.i.d. or t.i.d.). Subjects underwent weekly visits at which they were administered the 17-item Hamilton Rating Scale for Depression (HAM-D), Young Mania Rating Scale (YMRS), and Clinical Global Impressions scale (CGI). Every 2 weeks, subjects also underwent laboratory tests, a urine examination, and a verbal memory test. Outcome measures were analyzed with repeated-measures analysis of variance.

Results: Eight subjects completed all 8 weeks of the study. Two subjects completed more than 4 weeks of the study, and their data were analyzed using the last observation carried forward. Bipolar depression subjects had a significant reduction in HAM-D scores (p < .001) and in CGI-Improvement (CGI-I) scores (p < .001). Five of 8 subjects who completed all 8 weeks of the study had more than a 50% decrease in HAM-D scores and were rated much improved on the CGI-I at the end of 8 weeks of treatment. There was no significant drug effect on YMRS scores, weight, or verbal memory.

Conclusion: Zonisamide may be a useful drug in the treatment of bipolar depression. Further controlled clinical trials are needed.