Gabapentin and the Prophylaxis of Bipolar Disorders in Patients Intolerant to Lithium

Gabapentin (GBP) is a new anticonvulsant drug that has shown efficacy in the treatment of epilepsy, several neurological disorders (pain syndromes, acquired nystagmus, Huntington's chorea, amyotrophic lateral sclerosis), and more recently in the treatment of bipolar disorders. The aim of this preliminary study was to assess the efficacy of GBP as a mood stabiliser in bipolar disorders. The adverse events of GBP were also evaluated.

21 outpatients, 13 females and 8 males (mean age ± SD: 51.90 ± 11.51 years) affected by bipolar disorder (BD), in partial remission (DSM IV) and intolerant to lithium, were treated with GBP at a dose ranging from 300 to 2400 mg/day (mean ± SD: 1010.86 ± 268.55mg; 13.81 ± 4.21 mg/kg) for 1 year. Clinical assessments were performed with the Brief Psychiatric Rating Scale (BPRS), the Hamilton Rating Scale for Depression (HRS-D), the Hamilton Rating Scale for Anxiety (HRS-A) and the Manic Rating Scale (MRS) at baseline (T0), after 15 days (T0.5), after 30 days (T1), and then every month for 12 months.

Mean HRS-D, HRS-A and MRS scores did not show any significant variation during the study. Only one patient showed a clinical relapse. The most frequent adverse events reported by patients were dizziness (1%), dry mouth (1%) and sedation (0.5%). There was a significant negative correlation between GBP dosage (mg/kg) and HRS-A score. Mean leucocyte and neutrophil counts showed a significant increase during the study.

These preliminary data show potential efficacy and good tolerability of GBP in the prophylaxis of BD, but double-blind studies are required.