A 52-Week, Open-Label Continuation Study of Lamotrigine in the Treatment of Bipolar Depression

Background: Lamotrigine has demonstrated efficacy for the acute treatment of depression in bipolar I patients in a placebo-controlled, monotherapy study. We describe the results of a 52-week, open-label continuation of that trial.

Method: Patients meeting DSM-IV criteria for bipolar I disorder with a current major depressive episode who completed a 7-week, double-blind study of bipolar depression were offered 1 year of open-label lamotrigine therapy (flexible doses of 100-500 mg/day) in a continuation study. To maintain the acute study blind, the first 3 weeks of the continuation study remained blinded while patients previously randomly assigned to placebo were titrated to a lamotrigine dose of 50 mg/day. Patients who had been randomly assigned to lamotrigine continued at their fixed doses. Beginning at week 4, all patients received open-label lamotrigine for up to 49 additional weeks. Concomitant psychotropic medications were permitted during the open-label phase. Effectiveness (Montgomery-Asberg Depression Rating Scale [MADRS], Clinical Global Impressions-Improvement scale) and safety assessments were administered at weeks 4, 12, 24, 36, and 52. The study was conducted from June 1996 to December 1998.

Results: Of 135 patients completing the acute study, 124 (92%) entered the continuation study: 77 had received lamotrigine and 47 had received placebo in the acute study. The mean duration of lamotrigine exposure was 10.4 months, with a mean modal dose of 187 mg/day. Sixty-nine patients (56%) completed 1 year of treatment. Significant and sustained improvement from baseline was seen in mean observed MADRS scores (p < .05). The proportion of patients achieving remission (MADRS score <= 11) by week 4 of the study was 81.4%, and episodes of mania/hypomania occurred less frequently than in the preceding year. Headache was the most common drug-related adverse event.

Conclusion: During 1 year of open-label therapy with lamotrigine as adjunctive therapy or monotherapy, bipolar I patients experienced sustained improvement in depressive symptoms without evidence of mood destabilization.