Felbamate for refractory absence seizures

We treated 10 patients (aged 5–37 years) with medically refractory absence seizures with felbamate (FBM). Average duration of absence seizures was 16.2 years. All patients continued to have absence seizures at maximally tolerated doses of valproic acid and/or ethosuximide. At maximal FBM dosage (45 mg/kg/day or 3,600 mg/day), there was at least a 65% reduction in absence seizure frequency in eight patients; in four, there was a > 95% reduction. Mean duration of FBM therapy is 16.2 months (range, 5–31 months). Nine patients remain on FBM. Two patients are on FBM monotherapy; seven others are on FBM and one or two other antiepileptic drugs. FBM was discontinued in one patient who developed severe insomnia followed by a return to baseline absence seizure frequency after an initial good response, and an increase in generalized tonic-clonic seizures (GTCS). Three other patients also had a history of GTCS; in one there has been no significant change, whereas two have not had a GTCS during FBM therapy. Eight patients continue to have a clinically meaningful reduced absence seizure frequency, and eight patients reported fewer adverse effects with their current regimen including FBM. Tachyphylaxis to the antiabsence efficacy was observed in four cases. These preliminary findings suggest that FBM is useful in treating absence seizures.