Gabapentin treatment of the non-refractory bipolar spectrum: an open case series

OBJECTIVE: To determine if gabapentin is effective in monotherapy or add-on treatment of non-refractory bipolar disorder in open prospective treatment. METHODS: Charts of 21 outpatients meeting DSM-IV criteria for bipolar spectrum disorder (type I, type II, NOS, and cyclothymia) and who were treated with gabapentin were reviewed and clinical response was assessed based on prospective application of the Hamilton Depression Rating Scale (HDRS), the Young Mania Rating Scale (YMRS), the Clinical Global Impression scale (CGI), and the Global Assessment of Functioning scale (GAF). Also, response was rated retrospectively using the Clinical Global Impression scale for Bipolar Disorder (CGI-BP). RESULTS: Eight patients received gabapentin monotherapy and 13 received adjunctive therapy. Similar improvement in depression was noted in the monotherapy group, without induction of mania. Gabapentin was associated with a 43.8% improvement in manic symptoms and a 27.6% improvement in depressive symptoms in the overall sample. In the depressed subsample (n=10), there was a 57.5% improvement in depressive symptoms (P=0.10). Using the CGI-BP, gabapentin was moderately to markedly effective in 43% of patients for overall bipolar illness, 38% for depressive symptoms, and 25% for manic symptoms. Of those in the study, 62% reported side effects, mainly sedation and nausea, with 14% of the total sample discontinuing treatment due to adverse events. CONCLUSIONS: Gabapentin, either alone or as an adjunct, appeared moderately effective in treating depression in this small, uncontrolled, heterogeneous sample of non-refractory bipolar spectrum illness. Coupled with the earlier clinical literature, these data suggest the need for prospective double-blind studies of depressive illness in the bipolar spectrum.