Efficacy and tolerability of felbamate in adults with severe intellectual and developmental disabilities and drug-resistant epilepsy: A single-center evaluation.

INTRODUCTION: Adults with severe intellectual and developmental disabilities (IDD) frequently suffer from treatment-resistant epilepsy, often with early onset and multiple seizure types. Felbamate (FBM), initially promising for refractory epilepsy, fell out of favor following reports of aplastic anemia and hepatic failure. Subsequent analyses, however, partly mitigated these concerns.

METHODS: This retrospective, single-center, single-arm study assessed the long-term efficacy and safety of FBM in 92 adults with severe IDD and refractory epilepsy. Clinical effectiveness, tolerability, and retention were evaluated at two assessment points: T1 (∼6 months) and T2 (∼71 months) after therapy initiation. Secondary analyses explored associations with daily dose, serum concentration, and patient characteristics.

RESULTS: Mean treatment duration was 52.2 ± 46.2 months. Responder rates were 50.6% at T1 and 63.3% at T2; seizure freedom was achieved in 8.3% at T2. Effective doses ranged from 900 to 4,500 mg/day (serum levels: 17-122 µg/ml). The 5-year retention rate was 66%. Most discontinuations (69%) occurred within the first 12 months. Adverse effects occurred in 58%, most commonly appetite loss, fatigue, and sleep disturbances. Laboratory abnormalities (16.3%) were generally mild; two cases required intervention. No cases of aplastic anemia or liver failure were observed. No significant predictors of response or adverse effects were identified.

CONCLUSION: Felbamate may provide sustained clinical benefit in adults with severe IDD and refractory epilepsy when used under structured clinical and laboratory monitoring.