Classifications: anticonvulsant; Therapeutic:anticonvulsant
Pregnancy Category: C
400 mg, 600 mg tablets; 600 mg/5 mL suspension
Anticonvulsant mechanism has not been identified. Blocks repetitive firing of neurons and increases seizure threshold; prevents
Increases seizure threshold and prevents seizure spread.
Treatment of LennoxGastaut syndrome and partial seizures.
Monotherapy or in combination with other anticonvulsants for the treatment of generalized tonic/clonic seizures.
Hypersensitivity to felbamate, history of blood dyscrasia or hepatic dysfunction; pregnancy (category C).
Renal impairment, renal failure; older adults; hypersensitivity to other carbamates; thrombocytopenia; iron-deficiency anemia;
lactation. Safety and effectiveness in children other than those with LennoxGastaut syndrome are not established.
Route & Dosage
Adult: PO Initiate with 1200 mg/d in 34 divided doses, may increase by 600 mg/d q2wk (max: 3600 mg/d); when converting to monotherapy,
reduce dose of concomitant anticonvulsants by 1/3 when initiating felbamate, then continue to decrease other
anticonvulsants by 1/3 with each increase in felbamate q2wk; when using as adjunctive therapy, decrease other
anticonvulsants by 20% when initiating felbamate and note that further reductions in other anticonvulsants may be required
to minimize side effects and drug interactions
Child: PO Start at 15 mg/kg/d in 3 or 4 divided doses, reduce concurrent antiepileptic drugs by 20%, further reductions may be required
to minimize side effects due to drug interactions, may increase felbamate by 15 mg/kg/d at weekly intervals (max: 45 mg/kg/d)
- Do not give this drug to anyone with a history of blood dyscrasia or hepatic dysfunction.
- Titrate dose under close clinical supervision.
- Shake suspension well before giving a dose.
- Store in airtight container at room temperature, 15°30° C (59°86° F).
Adverse Effects (≥1%)CNS:
Mild tremors, headache, dizziness, ataxia, diplopia
, blurred vision; agitation, aggression, hallucinations, fatigue
Slight elevation of serum
cholesterol, hyponatremia, hypokalemia, weight gain and loss. GI: Nausea and vomiting,
, hiccup, taste disturbance, indigestion
, esophagitis, increased appetite, acute liver failure
. Hematologic: Aplastic anemia
Felbamate reduces serum carbamazepine
levels by a mean
of 25%, but increases levels of its active metabolite
, increases serum phenytoin
levels approximately 20%, and increases valproic acid
levels. Herbal: Gingko
may decrease anticonvulsant effectiveness.
90% from GI tract. Absorption of tablet not affected by food. Onset:
Therapeutic effect approximately 14 d. Peak:
levels at 16 h. Distribution:
2025% protein bound, readily crosses the bloodbrain barrier. Metabolism:
In the liver via the cytochrome P-450 system. Elimination:
4050% excreted unchanged in urine, rest excreted in urine as metabolites. Half-Life:
Assessment & Drug Effects
- Lab tests: Obtain baseline values for liver function and complete hematologic studies before initiating therapy, repeat frequently
during therapy, and for a lengthy period after discontinuation of felbamate. Monitor serum sodium and potassium levels periodically
because hyponatremia and hypokalemia have been reported.
- Report immediately any hematologic abnormalities.
- Monitor results of hepatic function tests throughout therapy.
- Note: When used concomitantly with either phenytoin or carbamazepine, carefully monitor serum levels of these drugs when felbamate
is added, when adjustments in felbamate dosing are made, or when felbamate is discontinued.
- Note: A reduction in phenytoin of 1040% is usually needed when felbamate is added to the regimen.
- Monitor weight, because both weight gain and loss have been reported.
- Monitor for S&S of drug toxicity including GI distress and CNS toxicity.
Patient & Family Education
- Note: It is highly recommended that patients and physicians review the indication for treatment, risks associated with the drug,
and the importance of undergoing regular blood monitoring.
- Report unusual changes (e.g., blurred vision, dysplopia) to physician.
- Report S&S of hypersensitivity including pruritus, urticaria, and (rarely) photosensitivity allergic reaction to physician.
- Learn adverse effects and report these to physician immediately.