Abstracts

Felbamate has not been commonly used as an antiepileptic drug (AED) due to its potential side effects of aplastic anemia and liver failure. However, in pediatric patients with Lennox-Gastaut syndrome (LGS) and other medically refractory epilepsies, it may be a very effective and well tolerated AED.
This study is a retrospective chart review of 38 pediatric patients with medically refractory epilepsy who were placed on felbamate. Seizure frequency was measured by daily seizure calendars and chart reports.
Felbamate was initially used as an adjunctive AED, combined with one or more other AEDs. The felbamate dosage range was 30-100 mg/kg/day. Average mean length of treatment was 12 months (range 1 month to 6 years). Age range was 6 months to 18 years, mean age 8 years. Predominant seizure type was tonic/generalized tonic-clonic (66%--25/38). Other seizure types included: (1) Atypical absence (37%--14/38); (2) Myoclonic-astatic (16%--6/38); (3) Myoclonic (13%--5/38); (4) Complex partial with secondary generalization (13%--5/38). The majority of patients had multiple seizure types. Epilepsy syndromes included: (1) LGS (58%--22/38); (2) Primary generalized epilepsy; probable myoclonic-astatic epilepsy of Doose (16%--6/38); (3) Symptomatic localization related epilepsy (13%--5/38); (4) Unclassified symptomatic generalized epilepsy. Seizure frequency was significantly reduced in the majority of patients: (1) 17% (6/38) remain completely seizure free; (2) 18% (7/38) had a greater than 75% reduction in seizure frequency; (3) 43% (16/38) had a greater than 50% reduction in seizure frequency; (4) 13% (5/38) had a greater than 25% reduction in seizure frequency; and (5) 5% (2/38) had no significant change in seizure control. One patient has just been started on felbamate. Side effects have been seen in 24% and have included insomnia, anorexia, and irritability. In only one patient have the side effects been significant enough to warrant discontinuation of felbamate. There have been no cases of aplastic anemia or liver dysfunction. 67% (4/6) of the patients who are seizure-free have probable myoclonic-astatic epilepsy of Doose--seizure onset between 2-5 years of age; primarily boys; myoclonic-astatic-absence seizures; electroencephalograms demonstrating irregular generalized polyspike and slow wave complexes with normal background. This epilepsy syndrome may represent a special subset that is exquisitely sensitive to felbamate, with dosages less than 50 mg/kg/day. The remainder had LGS with predominantly tonic seizures.
Felbamate appears to be a very effective, well tolerated, and safe AED in children with medically refractory epilepsy. Myoclonic-astatic epilepsy of Doose may constitute a subset of children with special sensitivity to felbamate treatment. No serious side effects were noted, despite therapy duration of 12 months or longer. This study is limited due to the small number of patients and its retrospective analysis. Further studies will be necessary to confirm the above results.