Effects of Topiramate

To the Editor: Drew H. Barzman, M.D., and Melissa P. DelBello, M.D., published a case report in the August 2006 edition of The American Journal of Psychiatry titled "Topiramate for Co-Occurring Bipolar Disorder and Disruptive Behavior Disorders" (1) . This case report suggests that topiramate is "helpful" in the treatment of bipolar disorder and that topiramate monotherapy may be "effective in treating disruptive behavior disorders independent of its therapeutic effect for mania that is possibly related to its efficacy in decreasing impulsivity in binge eating disorder, borderline personality disorder, and pathological gambling in adults” ( 1, p. 1452). The authors make a broad scientific claim regarding the benefits of topiramate. They suggest a link in efficacy for this anticonvulsant/anti-migraine agent based on observed diagnostic classification, but do not address the possibility that disorders that are related by phenotypic expression may be unrelated genotypically or mechanistically. We are concerned that the authors present information suggesting effectiveness of topiramate without offering balanced commentary regarding the significant side-effects of topiramate, including word-finding difficulty, impaired concentration, depression, confusion, encephalopathy, and memory interference (2, 3) . These and other problems with topiramate were recently highlighted elsewhere (4) .

Finally, we find little basis for the authors, suggestion that the actions of topiramate, a gamma-aminobutyric acidergic (GABAergic) drug, has beneficial effects independent of any possible antimanic effects. The statement that topiramate monotherapy may be similarly efficacious in treating disruptive disorders in children, gambling in adults, binge eating, and borderline personality disorder suggests a mechanism of action for topiramate that is not supported by current research.