BACKGROUND

Lamotrigine is approved as a maintenance therapy for bipolar I disorder in many countries, including China in 2021. This study evaluated the efficacy and safety of lamotrigine in controlling relapse and/or recurrence of mood episodes in Chinese patients with bipolar I disorder.

METHODS

Patients aged ≥ 18 years with bipolar I disorder who met response criteria (Clinical Global Impression-Severity [CGI-S] score of ≤ 3 for ≥ 4 consecutive weeks) during treatment with lamotrigine in a 6-16 week open-label (OL) phase, and who were maintained for ≥ 1 week on lamotrigine 200 mg/day monotherapy, were randomised (1:1) to continue receiving lamotrigine 200 mg/day or switch to placebo in a 36-week randomised double-blind (RD) phase. The primary efficacy outcome measure was time from entry into the RD phase to intervention for relapse and/or recurrence of a mood episode (TIME). Post hoc analyses assessed the impact of OL baseline mood severity on TIME. Safety assessments were conducted throughout the study.

RESULTS

Of 420 patients treated in the OL phase, 264 were randomised to receive lamotrigine (n = 131) or placebo (n = 133). Overall, 112 patients had an intervention for relapse and/or recurrence of a mood episode (lamotrigine, n = 50/130 [38.5%]; placebo, n = 62/133 [46.6%]), with no significant difference in TIME between groups (adjusted hazard ratio [95% confidence interval (CI)] 0.93 [0.64, 1.35]; p = 0.701). Post hoc analyses indicated a significant difference in TIME, favouring lamotrigine over placebo, for patients with baseline CGI-S score ≥ 4 (hazard ratio [95% CI] 0.52 [0.30, 0.89]; p = 0.018) and with baseline Hamilton Depression Rating Scale ≥ 18 or Young Mania Rating Scale ≥ 10 (0.44 [hazard ratio [95% CI] 0.25, 0.78]; p = 0.005). Lamotrigine was well tolerated with no new safety signals.

CONCLUSIONS

Lamotrigine was not significantly superior to placebo in preventing relapse and/or recurrence of mood episodes in this study of Chinese patients with bipolar I disorder but post hoc analyses suggested a therapeutic benefit in patients with moderate/severe mood symptoms at baseline. The discrepancy between these findings and the positive findings of the pivotal studies may be attributable to the symptom severity of the bipolar patients recruited, a high dropout rate, and the comparatively short duration of the RD phase rather than race/ethnicity differences. Clinical trial registration ClinicalTrial.gov Identifier NCT01602510; 21st May 2012; https://clinicaltrials.gov/ct2/show/NCT01602510 .