Preventive Effects of Lamotrigine in Bipolar II Versus Bipolar I Disorder

The preventive effects of mood stabilizers on recurrence/relapse in bipolar disorders have been investigated mostly in bipolar I disorder (BPI) patients, with limited reports on bipolar II disorder (BPII) patients. Here, we conducted an explorative data analysis to investigate whether the preventive effect of lamotrigine on recurrence /relapse in BPII is better than in BPI.

Data from Japanese patients with a diagnosis of BPI or BPII according to DSM-IV-TR were analyzed in an open-label, noninterventional, naturalistic, prospective postmarketing surveillance study of lamotrigine. This study was carried out from October 2011 to November 2014, and each patient was observed for 1 year. The time to recurrence/relapse of mood episodes after commencement of lamotrigine treatment was evaluated as a primary endpoint. Kaplan-Meier curves were generated to compare the time to recurrence/relapse of mood episodes in BPI with in BPII using a log-rank test.

Lamotrigine was associated with a significantly longer time to recurrence/relapse of mood episodes in BPII than in BPI (log-rank test, P = .0103). Lamotrigine also prolonged time to recurrence/relapse of mania-related episodes, including hypomanic episodes, more in BPII than in BPI (P = .0110).

Although the preventive effect of lamotrigine on recurrence/relapse of mood episodes in BPI has been established in a variety of clinical studies, the present study suggests that lamotrigine may be more suitable for maintenance treatment in BPII than in BPI.