Correlation between the Efficacy of Lamotrigine and the Serum Lamotrigine Level during the Remission Phase of Acute Bipolar II Depression: A Naturalistic and Unblinded Prospective Pilot Study

Lamotrigine has acute antidepressant effects in patients with bipolar disorder. However, there is little information regarding appropriate serum levels of lamotrigine and the time until remission after the start of lamotrigine therapy in patients with bipolar II depression. This was a naturalistic and unblinded prospective pilot study. Twelve patients' depressive symptoms were evaluated using the Montgomery-Asberg Depression Rating Scale (MADRS) at the start of treatment and at the time of remission, and blood samples were obtained at the time of remission. Mahalanobis distance was used to analyze the relationship between the MADRS improvement rate and the serum lamotrigine level. Furthermore, we calculated the Spearman's rank correlation coefficient for the relationship between the MADRS improvement rate and the serum lamotrigine level, and produced box plots of the serum lamotrigine level at remission and the time until remission. The Mahalanobis distance for the patient that was co-administered lamotrigine and valproic acid differed significantly from those of the other patients (p