Section 01 · Monograph
Felbamate
Reviewed Nov 2026FDA label
FelbatolNMDA antagonist
- Forms
- Tab: 400, 600mg | Susp: 600mg/5mL
- Dose
- 1200-3600mg/day divided
- MOA
- NMDA blockade + GABA-A potentiation
Black Box Warning
- Aplastic anemia: markedly increased incidence, estimated at roughly 100-fold the background rate; onset typically 5-30 weeks after starting therapy; routine blood monitoring cannot reliably predict or prevent aplastic anemia
- Hepatic failure: cases of acute liver failure, some fatal, reported; onset can be rapid — discontinue immediately if hepatic dysfunction is suspected
- Because of these risks, felbamate should be reserved for patients whose epilepsy is so severe that the risk is deemed acceptable, only after full discussion of risks and informed consent/acknowledgment
Indications
- Adjunctive or monotherapy for partial-onset seizures (with or without generalization) in adults, reserved for epilepsy refractory to other treatmentsFDA-labeled
- Adjunctive therapy for seizures associated with Lennox-Gastaut syndrome in childrenFDA-labeled
Mechanism of Action
- Exact mechanism unknown; thought to act as an antagonist at the strychnine-insensitive glycine recognition site of the NMDA receptor complex, and may also potentiate GABA-A receptor activity
- Weak inhibitory activity at voltage-gated sodium and calcium channels also described
Full Dosing
Adult / usual
- Adults/adolescents ≥14 years: initiate 1200mg/day in 3-4 divided doses (with concurrent reduction of other AEDs by ~20-33%); increase in 600mg/day increments at weekly intervals; usual maintenance up to 3600mg/day
Renal
- Reduce dose by approximately 50% in renal impairment
Pediatric
- Children 2-14 years (Lennox-Gastaut, adjunctive): initiate 15mg/kg/day in divided doses, increasing by 15mg/kg/day at weekly intervals to a target of 45mg/kg/day, with reduction of other AEDs
Contraindications
- Known hypersensitivity to felbamate or other carbamates
- History of any blood dyscrasia
- History of hepatic dysfunction
Drug Interactions
- Increases phenytoin and valproate concentrations — reduce phenytoin dose by ~20-30% when initiating felbamate
- Decreases carbamazepine levels while increasing its active epoxide metabolite; monitor levels
- Phenytoin and carbamazepine each decrease felbamate concentrations by roughly 40-50%
- Numerous other AED interactions — requires close level monitoring and dose adjustment when starting or stopping felbamate
Adverse Effects
- Common: anorexia, nausea, vomiting, insomnia, headache, dizziness, somnolence, weight loss
- Serious: aplastic anemia and hepatic failure (see boxed warning)
- Rare: Stevens-Johnson syndrome, toxic epidermal necrolysis, pancreatitis
- Suicidal ideation/behavior (class effect of AEDs)
Monitoring Parameters
- Baseline CBC with platelets/reticulocytes and liver function tests before starting, with frequent monitoring during therapy — though this cannot reliably predict aplastic anemia
- Discontinue if AST/ALT rises to ≥2x upper limit of normal or if signs of bone marrow suppression develop
- Written informed consent/acknowledgment of risks recommended before initiation
- Monitor concomitant AED levels closely when starting or stopping felbamate
Pregnancy & Lactation
- Limited human data; animal studies showed decreased offspring weight and survival. Use only if potential benefit justifies fetal risk. NAAED Pregnancy Registry enrollment encouraged (1-888-233-2334)
- Felbamate is excreted in human breast milk; effect on the nursing infant is unknown