There is a pressing need for additional treatment options for refractory mood disorders. This controlled comparative study evaluated the efficacy of lamotrigine (LTG) and gabapentin (GBP) monotherapy versus placebo (PLC). Thirty-one patients with refractory bipolar and unipolar mood disorders participated in a double-blind, randomized, crossover series of three 6-week monotherapy evaluations including LTG, GBP, and PLC. There was a standardized blinded titration to assess clinical efficacy or to determine the maximum tolerated daily dose (LTG 500 mg or GBP 4,800 mg). The primary outcome measure was the Clinical Global Impressions Scale (CGI) for Bipolar Illness as supplemented by other standard rating instruments. The mean doses at week 6 were 274 ± 128 mg for LTG and 3,987 ± 856 mg for GBP. Response rates (CGI ratings of much or very much improved) were the following: LTG, 52% (16/31); GBP, 26% (8/31); and PLC, 23% (7/31) (Cochran's Q = 6.952, df = 2, N = 31, p = 0.031). Post hoc Q differences (df = 1, N = 31) were the following: LTG versus GBP (Q diff = 5.33, p = 0.011); LTG versus PLC (Q diff = 4.76, p = 0.022); and GBP versus PLC (Q diff = 0.08, p = 0.70). With respect to anticonvulsant dose and gender, there was no difference between the responders and the nonresponders. The agents were generally well tolerated. This controlled investigation preliminarily suggests the efficacy of LTG in treatment-refractory affectively ill patients. Further definition of responsive subtypes and the role of these medications in the treatment of mood disorders requires additional study.
*Biological Psychiatry Branch and †Laboratory of Clinical Science, National Institute of Mental Health, National Institutes of Health, Bethesda, Maryland; ‡University of California, Los Angeles, School of Medicine, Los Angeles; §Stanford University School of Medicine, Stanford, California; ∥University of Arkansas School of Medicine, Little Rock, Arkansas
Received August 25, 1999; accepted after revision December 13, 1999.
Presented, in part, at the 150th Annual Meeting of the American Psychiatric Association, May 20, 1997, San Diego, CA, and the 151st Annual Meeting of the American Psychiatric Association, June 3, 1998, Toronto, ON, Canada.
Address requests for reprints to: Robert M. Post, MD, Biological Psychiatry Branch, National Institute of Mental Health, Building 10, Room 3N212, 10 Center Drive, MSC 1272, Bethesda, MD 20892-1272.