Lamotrigine versus lithium as maintenance treatment in bipolar I disorder: an open, randomized effectiveness study mimicking clinical practice. The 6th trial of the Danish University Antidepressant Group (DUAG-6).

OBJECTIVES: In industry-generated pivotal studies, lamotrigine has been found to be superior to placebo and comparable to lithium in the maintenance treatment of bipolar I disorder. Here, we directly compared lamotrigine to lithium under conditions similar to clinical routine conditions.

METHODS: Adult bipolar I disorder patients with at least two episodes within the last five years and an index episode requiring treatment were randomized to lithium (n = 78; doses adjusted to obtain serum levels of 0.5-1.0 mmol/L) or to lamotrigine (n = 77; up-titrated to 400 mg/day) as maintenance treatments. Randomization took place when clinically appropriate, and comedication was allowed within the first six months after randomization. The patients were enrolled from March 2001 to December 2005, and observations were censored December 2006, allowing a subgroup of patients to be followed for more than five years. The primary outcome measure was time to predefined endpoints indicating insufficient maintenance treatment, and the major secondary outcome measure was time to any study endpoint. Data were analyzed primarily by Cox proportional regression models.

RESULTS: For the primary outcome measure, the crude Hazard Rate Ratio (HRR) (lamotrigine relative to lithium) was 0.92 [95% confidence interval (CI): 0.60-1.40]. When the primary endpoints were broken down by polarity, the HRRs (lamotrigine relative to lithium) for mania and depression were, respectively, 1.91 (95% CI: 0.73-5.04) and 0.69 (95% CI: 0.41-1.22). There was no between-group difference in terms of staying in study [HRR: 0.85 (95% CI: 0.61-1.19)]. Most treatment failures occurred within the first 1.5 years of treatment, and, among patients followed for at least five years, practically no patients were maintained successfully on monotherapy with either of the drugs. The lithium-treated patients reported diarrhea, tremor, polyuria, and thirst more frequently. Two cases, probably lamotrigine-related, of benign rash occurred.

CONCLUSIONS: No differences in maintenance effectiveness between lithium and lamotrigine could be demonstrated. Lamotrigine was better tolerated than lithium, but apparently this did not influence the outcome.