The clinical effectiveness and cost effectiveness of lamotrigine for people with borderline personality disorder: a randomized, placebo-controlled trial

Objectives: To examine whether lamotrigine is a clinically effective and cost-effective treatment for people with borderline personality disorder.Method: Multicentre, double-blind, placebo-controlled randomized trial. Between July 2013 to November 2016, we recruited 276 people aged 18 or over, who met diagnostic criteria for borderline personality disorder. We excluded those with co-existing bipolar affective disorder or psychosis, those already taking a mood stabiliser, and women at risk of pregnancy. We randomly allocated participants on a 1:1 ratio to up to 400mg of lamotrigine per day or an inert placebo using a remote web-based randomization service. The primary outcome was total score on the Zanarini Rating scale for Borderline Personality Disorder (ZAN-BPD) at 52 weeks. Secondary outcomes included depressive symptoms, deliberate self-harm, social functioning, health-related quality of life, resource use and costs, side effects of treatment and adverse events.Results: 195 (70.6%) participants were followed up at 52 weeks, at which point 49 (36%) of those prescribed lamotrigine and 58 (42%) of those prescribed placebo were taking it. Mean total ZAN-BPD score was 11.3 (SD = 6.6) among those randomized to lamotrigine and 11.5 (SD = 7.7) among those randomized to placebo (adjusted difference in means = 0.1, 95% C.I = -1.8 to 2.0, p=0.91). There was no evidence of any differences in secondary outcomes. Costs of direct care for those prescribed lamotrigine were similar to those prescribed placebo.Conclusions: Treating people with borderline personality disorder with lamotrigine is not a clinically effective or cost-effective use of resources