Effectiveness of antiepileptic drugs for the treatment of bipolar disorder: findings from a systematic review

Abstract

Bipolar disorder is characterized by chronic and recurrent symptoms including mania, hypomania, and depressive and mixed episodes, with approximately 5.7 million Americans over age 18, or 2.6% of the U.S. population, suffering from the illness. The prevalence of the disorder may be higher due to its chronic and recurrent nature. Individuals with bipolar disorder often first present in general medical settings with depressive symptomatology. Long-term management typically occurs in mental health settings by psychiatrists or other mental health specialists. While there have been major advances in pharmacotherapy for bipolar disorder, evidence-based information on drug effectiveness is not always easily accessible to prescribers in daily practice. Available information has sometimes led to inappropriate use of various classes of drugs, specifically antiepileptic drugs (AEDs), for bipolar disorder. Originally approved in 1993 by the U.S. Food and Drug Administration (FDA) only for adjunctive treatment of partial complex seizures, the manufacturer of gabapentin (Neurontin), an AED, promoted its off-label use for treatment of psychiatric disorders, including bipolar disorder. The efficacy of the drug for this indication had not been demonstrated, nor had the manufacturer sought FDA approval for the indication. In 2004, 50 Attorneys General settled consumer protection claims regarding alleged deceptive off-label marketing practices of Pfizer subsidiary Warner-Lambert. At about the same time, a consortium of State Medicaid agencies funded a drug class review to compare effectiveness and adverse event profiles of AEDs in the treatment of bipolar mood disorder, neuropathic pain, and fibromyalgia. This article presents a summary of the findings from the drug class review related to prescription of the AEDs in bipolar disorder.