Background: The anticonvulsant lamotrigine was previously shown to be effective for bipolar depression. This study assessed the efficacy and tolerability of lamotrigine and lithium compared with placebo for the prevention of mood episodes in bipolar disorder.
Method: During an 8- to 16-week open-label phase, lamotrigine (titrated to 200 mg/day) was added to current therapy for currently or recently depressed DSM-IV-defined bipolar I outpatients (N = 966) and concomitant drugs were gradually withdrawn. Patients stabilized on open-label treatment (N = 463) were then randomly assigned to lamotrigine (50, 200, or 400 mg/day; N = 221), lithium (0.8-1.1 mEq/L; N = 121), or placebo (N = 121) monotherapy for up to 18 months. The primary outcome measure was time from randomization to intervention (addition of pharmacotherapy) for any mood episode (depressive, manic, hypomanic, or mixed). Data were gathered from September 1997 to August 2001.
Results: Time to intervention for any mood episode was statistically superior (p = .029) for both lamotrigine and lithium compared with placebo-median survival times were 200, 170, and 93 days, respectively. Intervention for depression was more frequent than for mania by a factor of nearly 3:1. Lamotrigine was statistically superior to placebo at prolonging the time to intervention for a depressive episode (p = .047). The proportions of patients who were intervention-free for depression at 1 year were lamotrigine 57%, lithium 46%, and placebo 45%. Lithium was statistically superior to placebo at prolonging the time to intervention for a manic or hypomanic episode (p = .026). The proportions of patients who were intervention-free for mania at 1 year were lamotrigine 77%, lithium 86%, and placebo 72%. Headache was the most frequent adverse event for all 3 treatment groups.
Conclusion: Lamotrigine and lithium were superior to placebo for the prevention of mood episodes in bipolar I patients, with lamotrigine predominantly effective against depression and lithium predominantly effective against mania.