A Partial Response at Week 4 Can Predict Subsequent Outcome during Lamotrigine Augmentation Therapy in Treatment-Resistant Depressive Disorder: A Preliminary Study

Background/Aims: The present study prospectively examined whether or not a partial response at week 4 predicts subsequent response at week 8 during lamotrigine augmentation therapy in 51 (16 males and 35 females) inpatients with treatment-resistant depressive disorder using an open-study design. Methods: The subjects were 51 depressed patients who had already shown insufficient response to at least 3 psychotropics including antidepressants, mood stabilizers, and atypical antipsychotics. The diagnoses were major depressive disorder (n = 19), bipolar I disorder (n = 9), and bipolar II disorder (n = 23). The final doses of lamotrigine were 100 mg/day for 29 subjects who were not taking valproate and 75 mg/day for 22 subjects taking valproate. Depressive symptoms were evaluated by the Montgomery-Åsberg Depression Rating Scale (MADRS) before the start of lamotrigine and then at week 4, and finally after the 8th week of treatment. Results: A significant linear relationship was found between percent improvements in MADRS scores at weeks 4 and 8 (r = 0.492, y = 0.438x + 30.223, R2 = 0.226, p < 0.001). The receiver operating characteristics analysis indicated that a percent improvement of 16% or greater at week 4 was significantly (p < 0.01) predictive of response (50% or more reduction in the MADRS score). The patients were significantly divided by the cut-off point into the responders and the nonresponders (18/26 vs. 1/25, p < 0.001). Conclusion: The present study suggests that a partial response at week 4 can predict subsequent outcome at week 8 during lamotrigine augmentation therapy in patients with treatment-resistant depressive disorder, and that the absence of a partial improvement at week 4 is highly predictive of nonresponse.