FELBAMATE FOR REFRACTORY ABSENCE SEIZURES

We treated 10 patients (aged 5-37 years) with medically refractory abs ence seizures with felbamate (FBM). Average duration of absence seizur es was 16.2 years. All patients continued to have absence seizures at maximally tolerated doses of valproic acid and/or ethosuximide. At max imal FBM dosage (45 mg/kg/day or 3,600 mg/day), there was at least a 6 5% reduction in absence seizure frequency in eight patients; in four, there was a > 95% reduction. Mean duration of FBM therapy is 16.2 mont hs (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 anti epileptic drugs. FBM was discontinued in one patient who developed sev ere insomnia followed by a return to baseline absence seizure frequenc y after an initial good response, and an increase in generalized tonic -clonic seizures (GTCS). Three other patients also had a history of GT CS; in one there has been no significant change, whereas two have not had a GTCS during FBM therapy. Eight patients continue to have a clini cally meaningful reduced absence seizure frequency, and eight patients reported fewer adverse effects with their current regimen including F BM. Tachyphylaxis to the antiabsence efficacy was observed in four cas es. These preliminary findings suggest that FBM is useful in treating absence seizures.