Anticonvulsants in the treatment of mood disorders: assessing current and future roles

Anticonvulsants are frequently used in the treatment of affective illnesses, especially for patients refractory to or intolerant of other treatments. The differential therapeutic roles of anticonvulsants, however, remain largely undetermined. The author reviews the available efficacy data for carbamazepine, oxcarbazepine, valproate, lamotrigine, gabapentin and topiramate. Valproate is efficacious in the monotherapy of acute manic presentations but confirmatory evidence of the efficacy of valproate in long-term maintenance has been elusive. Valproate and possibly carbamazepine, may provide a therapeutic advantage over lithium in non-classic bipolar conditions such as mixed mood states and rapid cycling conditions. Lamotrigine is unique among the anticonvulsants in its monotherapy efficacy for bipolar I depression. Emerging data also suggest a role for lamotrigine in the adjunctive treatment of depressive mixed states and rapid cycling conditions in the absence of prominent manic symptoms. Controlled trials have found gabapentin ineffective for acute mania and refractory bipolar conditions. The role of gabapentin in the treatment of other aspects of affective illness remains uncertain. Definitive statements regarding the differential psychotropic use of topiramate and oxcarbazepine are not possible, though active investigation is underway to better characterise the utility of topiramate. The author suggests that current diagnostic models utilised in controlled trials may limit identification of differential therapeutic benefits. Caution is advised in generalising from the ability or inability of an agent to demonstrate antimanic activity. Future studies of newer anticonvulsants should include dimensional perspectives and soft bipolar presentations, as the greatest contribution of the newer anticonvulsants may be in treatment of mood conditions other than acute mania.