Clinical studies on the use of lamotrigine in bipolar disorder.

New mood stabilizers that possess efficacy in the depressed phase of bipolar disorder are needed. The use of marketed antidepressants puts bipolar patients at some increased risk for drug-induced hypomania/mania and rapid cycling. During the development of the antiepileptic, lamotrigine, the drug was observed to improve mood, alertness, and social interactions in some patients with epilepsy. These early observations provided the rationale for investigations into lamotrigine's potential efficacy in bipolar disorder. There are now 14 open clinical reports involving a total of 207 lamotrigine-treated patients with bipolar disorder that suggest this drug possesses a broad spectrum of efficacy in the management of the depressed, hypomanic, manic, and mixed phases of bipolar disorder. In an attempt to replicate and extend these preliminary open-label prospective findings, a series of multicenter, double-blind, placebo-controlled studies evaluating the efficacy and dose-response relationships of lamotrigine in the various phases of the illness, including both acute and maintenance designs in both bipolar I and II disorder, is ongoing.