Background: Gabapentin is an anticonvulsant proposed to have mood-stabilizing properties. It has been effective in the add-on treatment of refractory partial seizures and secondary generalized tonic-clonic seizures. It has the advantage of a favorable side effect profile and lack of drug interactions.
Methods: Twelve consecutive outpatients with persistent, treatment-resistant bipolar spectrum disorders were treated with gabapentin in combination with other medications. Patients were started at 300 mg/day, which was titrated according to clinical response. Response was assessed every 3-4 weeks with a Clinical Global Improvement Scale. Dosage and side effects were noted. The median peak dose was 2400 mg/day.
Results: One patient had a marked response to gabapentin; seven, a moderate response; two, mild; and two, no response to treatment. Six patients discontinued treatment due to somatic complaints (i.e., sedation or fatigue). The most frequently reported adverse effect was sedation.
Limitations: Gabapentin was added openly, and rating was nonblind in this case series. The use of concomitant medications could have increased the amount of sedation experienced with gabapentin.
Conclusion: Overall, gabapentin was associated with moderate improvement of mood symptoms. Given the severity and chronicity of these patients' illness, a moderate response must be considered a relative success. Controlled studies of gabapentin are needed to clarify its role in the treatment of bipolar disorder.