Efficacy of Newer Anticonvulsant Medications in Bipolar Spectrum Mood Disorders

Background: More treatment options for all phases of bipolar disorder are needed. While lithium, valproate, and carbamazepine remain the standard of care for treatment of bipolar disorder, many patients do not respond adequately to these treatments. Some new antiepileptic medications such as lamotrigine, gabapentin, topiramate, oxcarbazepine, tiagabine, and zonisamide are beginning to be used to treat bipolar disorder. Data Sources: Evidence for effectiveness of these novel antiepileptic drugs in treating acute mania and depression as well as in preventing the recurrence of mania and depression is reviewed. A MEDLINE search (1966-2001) was performed for clinical trials that were published in English using the keywords lamotrigine, gabapentin, topiramate, oxcarbazepine, tiagabine, and zonisamide, plus the terms bipolar disorder and mania. Evidence for effectiveness of monotherapy is presented first when it is available. Data from augmentation treatment studies and open case series in which standard ratings of symptoms were employed are presented when these are the only available data. Data Synthesis: Twenty-eight reports of the efficacy of novel antiepileptic medications in bipolar disorder are reviewed. Evidence is strongest for lamotrigine monotherapy in patients with bipolar depression, in some patients with rapid-cycling bipolar disorder, and as prophylaxis. Evidence for the efficacy of topiramate in acute and refractory mania is promising but comes predominantly from open trials. Although some very small studies have found that oxcarbazepine and zonisamide may have some effectiveness for treating mania, these data are very preliminary. Results are mixed from the 2 small open trials of tiagabine. Although gabapentin is widely used in bipolar disorder, controlled data do not support the use of gabapentin as an antimanic medication or mood stabilizer. Conclusion: More controlled trials are needed to assess the effectiveness of novel antiepileptic medications in bipolar disorder.