Clinical Experience with Felbamate in Patients with Medically Intractable Epilepsy

RATIONALE: Felbamate (FBM) use has declined since 1994 following reports of FBM induced aplastic anemia and liver failure. Limited published data is available on the clinical experience of FBM use since 1994. We previously presented a preliminary report on a limited sample of adult patients treated at Minnesota Epilepsy Group. The current study significantly expands our observations on Felbamate therapy and includes results on pediatric as well as adult patients. METHODS: 305 patients ages 1 to 73 yrs. treated with FBM were identified and records reviewed. Data were tabulated and analyzed to include patient demographics, efficacy and tolerability. Paired t tests were calculated to compare me an seizure frequency prior to FBM use and at FBM optimization. RESULTS: Of patients reviewed, 147 female/158 were male. Mean age at start of FBM was 32 yrs. for adults (>16 years) and 6.8 yrs for children (<16 years). The mean number failed AEDs was 5.5. Mean baseline frequency/seizure type/month: GTCs 19 for children/7.9 for adults; CPSs 28.7 for children/27.3 for adults; SPS 9.5 for children/27.3 for adults; tonic seizures 28.7 for children/102.1 for adults; myoclonic 26 for children/121.2 for adults; atonic 10 for children/20.4 for adults. FBM therapy ranged from 1 to 156 months (mean: 36.3) with an average maximum dose of 2,240-mg/day for children/3,769.3-mg/day for adults. The average FBM level was 73-mg/dl for adults/72.3-mg/dl for children. Responder rate (50% reduction in baseline seizure frequency) was 57% for children, 41% of those with >75% reduction. For adults, the responder rate was 66%, 49% having >75% reduction. Average reduction in baseline frequency per seizure type became seizure free. 59% of adults and 68% of children remain on FBM. Reasons for discontinuation included intolerable side effects, no perceived benefit in seizure reduction, anticipating pregnancy, and the announcement of the risk of aplastic anemia. Side effects documented included insomnia, behavioral changes, decreased appetite and headache. One patient developed aplastic anemia. No hepatic complications were documented. CONCLUSION: In patients with intractable seizures including GTCs, CPS, tonic and myoclonic seizures, FBM is significantly effective in reducing mean baseline seizure frequency with some patients becoming seizure free. FBM remains an important treatment consideration in patients with intractable epilepsy.