Background: Carbamazepine is frequently used for treating bipolar disorder, but few large trials have assessed its efficacy in preventing relapse. We evaluated open-label monotherapy with beaded extended-release carbamazepine capsules (ERC-CBZ; SPD417) as continuation and short-term maintenance therapy in bipolar disorder patients with manic and mixed episodes.
Method: A 6-month, open-label study enrolled 92 patients with DSM-IV bipolar disorder (most recent episode: 67% [N = 62] mixed, 33% [N = 30] manic) who had participated in 2 previous 3-week, double-blind, placebo-controlled studies. Subjects received beaded ERC-CBZ (200-1600 mg/day), titrated at investigators' discretion to a final mean dose of 938 mg/day and serum carbamazepine concentration of 6.6 microg/mL. The primary efficacy measure was time to relapse, and secondary efficacy measures included Young Mania Rating Scale (YMRS), Clinical Global Impressions scale (CGI), and Hamilton Rating Scale for Depression (HAM-D) scores. Data were gathered from January 2000 to January 2002.
Results: Of 77 patients analyzed in the intent-to-treat population, 11 (14.3%) relapsed. Fifty-three patients (68.8%) discontinued early, including 18 (23.4%) due to adverse events. Observed mean time to relapse was 61.1 days, while estimated mean time to relapse based on the Kaplan-Meier model was 141.8 days. Improvements on the YMRS, CGI, and HAM-D from the beginning of prior double-blind treatment were maintained. The most common adverse events were headache, dizziness, and rash. No significant weight gain was noted.
Conclusion: We noted a low relapse rate with beaded ERC-CBZ in this 6-month trial. Adverse events were generally mild to moderate and were typical of those associated with carbamazepine. Controlled studies are warranted to further explore the efficacy of beaded ERC-CBZ in preventing relapse in bipolar disorder.