A Multicenter, Randomized, Double-Blind, Placebo-Controlled Trial of Extended-Release Carbamazepine Capsules as Monotherapy for Bipolar Disorder Patients With Manic or Mixed Episodes

Background: Carbamazepine has been used to treat mania for over 2 decades. Most evaluations of carbamazepine have had important limitations, such as absence of a parallel placebo group, small sample size, or the confounding influence of concomitant treatment. All studies have used conventional, immediate-release carbamazepine formulations. We assessed the efficacy and safety of monotherapy with beaded, extended-release carbamazepine capsules (ERC-CBZ; SPD417) in bipolar disorder patients with manic or mixed episodes.

Method: Following a single-blind placebo lead-in, DSM-IV-defined bipolar disorder patients with manic or mixed episodes were randomly assigned to receive ERC-CBZ (N = 101) or placebo (N = 103) for 3 weeks. Patients were hospitalized through the first 7 days of the double-blind period. ERC-CBZ was initiated at 400 mg/day and increased, as necessary and tolerated, up to 1600 mg/day. Efficacy was assessed weekly with the Young Mania Rating Scale (YMRS), Clinical Global Impressions scale (CGI), and Hamilton Rating Scale for Depression (HAM-D). Data were gathered from December 1999 to June 2001.

Results: Ninety-six (47.1%) of 204 patients completed the study. The mean ± SD final ERC-CBZ dose was 756.44 ± 413.38 mg/day with a mean plasma drug level of 8.9 mg/mL. Starting at week 2, ERC-CBZ was associated with significantly greater improvements in YMRS (p = .032) using last-observation-carried-forward analyses. At end point, the responder rate (patients with at least a 50% decrease in YMRS score) also favored ERC-CBZ (41.5% vs. 22.4%; p = .0074). In a post hoc analysis of mixed patients, HAM-D score was significantly improved in patients remaining on ERC-CBZ treatment on day 21 (p = .01). Adverse events occurring more frequently in the ERC-CBZ group than in the placebo group included dizziness, nausea, and somnolence.

Conclusion: We found ERC-CBZ to be effective in the first large, randomized, double-blind, placebo-controlled parallel trial of carbamazepine monotherapy in acute mania. This trial provides important additional evidence supporting the use of carbamazepine in acute mania.