Felbamate tablets have been studied as monotherapy and adjunctive therapy in adults and as adjunctive therapy in children with seizures associated with Lennox-Gastaut syndrome. As felbamate tablets are added to or substituted for existing AEDs, it is strongly recommended to reduce the dosage of those AEDs in the range of 20 to 33% to minimize side effects (see Drug Interactions subsection).

Dosage Adjustment in the Renally Impaired: Felbamate should be used with caution in patients with renal dysfunction. In the renally impaired, starting and maintenance doses should be reduced by one-half (see CLINICAL PHARMACOLOGY / Pharmacokinetics and PRECAUTIONS). Adjunctive therapy with medications which affect felbamate plasma concentrations, especially AEDs, may warrant further reductions in felbamate daily doses in patients with renal dysfunction.

Adults (14 years of age and over)

The majority of patients received 3600 mg/day in clinical trials evaluating its use as both monotherapy and adjunctive therapy.

Monotherapy: (Initial therapy) Felbamate tablets have not been systematically evaluated as initial monotherapy. Initiate felbamate tablets at 1200 mg/day in divided doses three or four times daily. The prescriber is advised to titrate previously untreated patients under close clinical supervision, increasing the dosage in 600-mg increments every 2 weeks to 2400 mg/day based on clinical response and thereafter to 3600 mg/day if clinically indicated.

Conversion to Monotherapy: Initiate felbamate tablets at 1200 mg/day in divided doses three or four times daily. Reduce the dosage of concomitant AEDs by one-third at initiation of felbamate tablets therapy. At week 2, increase the felbamate tablets dosage to 2400 mg/day while reducing the dosage of other AEDs up to an additional one-third of their original dosage. At week 3, increase the felbamate tablets dosage up to 3600 mg/day and continue to reduce the dosage of other AEDs as clinically indicated.

Adjunctive Therapy: Felbamate tablets should be added at 1200 mg/day in divided doses three or four times daily while reducing present AEDs by 20% in order to control plasma concentrations of concurrent phenytoin, valproic acid, phenobarbital, and carbamazepine and its metabolites. Further reductions of the concomitant AEDs dosage may be necessary to minimize side effects due to drug interactions. Increase the dosage of felbamate tablets by 1200 mg/day increments at weekly intervals to 3600 mg/day. Most side effects seen during felbamate tablets adjunctive therapy resolve as the dosage of concomitant AEDs is decreased.

While the above felbamate tablets conversion guidelines may result in a felbamate tablets 3600 mg/day dose within 3 weeks, in some patients titration to a 3600 mg/day felbamate tablets dose has been achieved in as little as 3 days with appropriate adjustment of other AEDs.

Children with Lennox-Gastaut Syndrome (Ages 2 to 14 years)

Adjunctive Therapy: Felbamate tablets should be added at 15 mg/kg/day in divided doses three or four times daily while reducing present AEDs by 20% in order to control plasma levels of concurrent phenytoin, valproic acid, phenobarbital, and carbamazepine and its metabolites. Further reductions of the concomitant AEDs dosage may be necessary to minimize side effects due to drug interactions. Increase the dosage of felbamate tablets by 15 mg/kg/day increments at weekly intervals to 45 mg/kg/day. Most side effects seen during felbamate tablets adjunctive therapy resolve as the dosage of concomitant AEDs is decreased.