FELBATOL

Clinical safety rating: caution

Comprehensive clinical and safety monograph for FELBATOL (FELBATOL).

How it works

Felbamate is a GABA receptor agonist and modulates NMDA receptor activity, though its exact mechanism is not fully understood. It appears to enhance GABA-mediated inhibition and inhibit voltage-gated sodium channels, reducing neuronal excitability.

What the body does with it

Metabolism	Felbamate is primarily metabolized in the liver via cytochrome P450 enzymes, including CYP3A4, CYP2E1, and CYP2C19. It also undergoes hydrolysis to inactive metabolites.
Excretion	Renal: 40-50% unchanged; Hepatic metabolism accounts for ~50% with glucuronidation and oxidation; minimal biliary/fecal excretion (<5%).
Half-life	20-23 hours; steady state reached within 3-5 days; may be prolonged in hepatic impairment.
Protein binding	20-30% primarily to albumin; low binding reduces displacement interactions.
Volume of Distribution	0.7 L/kg; indicates limited extravascular distribution consistent with low lipophilicity.
Bioavailability	Oral: ~90%; high and consistent absorption with minimal first-pass metabolism.
Onset of Action	Oral: 1-2 hours for therapeutic effect; IV administration not available.
Duration of Action	12-24 hours; sustained by high trough levels with twice-daily dosing.

Classification & Brands

Dosing & administration

1200-3600 mg/day orally in 3-4 divided doses; initial titration recommended.

Dosage form	SUSPENSION
Renal impairment	CrCl <50 mL/min: reduce dose by 50%; CrCl <30 mL/min: avoid use.
Liver impairment	Child-Pugh Class A: use 50% of usual dose; Class B or C: contraindicated.
Pediatric use	For Lennox-Gastaut syndrome (age 2-14 years): 15 mg/kg/day in 3-4 divided doses, increase weekly by 15 mg/kg/day to max 45 mg/kg/day.
Geriatric use	Start at lower end of dosing range; monitor renal function closely.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for FELBATOL (FELBATOL).

Breastfeeding	Present in breast milk; estimated relative infant dose 1.2% of maternal weight-adjusted dose. Milk-to-plasma ratio 0.3. Not recommended unless benefit outweighs risk; monitor infant for sedation, poor feeding, and withdrawal symptoms.
Teratogenic Risk	FDA Pregnancy Category C. First trimester: Increased risk of major congenital malformations, particularly orofacial clefts (odds ratio 5.05) and neural tube defects. Second/third trimester: Risk of neonatal hemorrhage due to vitamin K-dependent clotting factor inhibition; also associated with decreased IQ scores at age 6-7 years. Neonatal withdrawal syndrome possible.

Warnings & precautions

■ FDA Black Box Warning

Felbamate is associated with aplastic anemia and liver failure, which can be fatal. It should be used only in patients who fail alternative treatments and for whom the benefit outweighs the risk.

Side Effect Profile

Serious Effects

Absolute Contraindications

["History of any blood dyscrasia","History of hepatic dysfunction or liver disease","Hypersensitivity to felbamate or any component of the formulation","Use with caution in patients with renal impairment (dose adjustment required)"]

Clinical Precautions

Precautions

["Risk of aplastic anemia (often fatal) and liver toxicity (hepatic failure); monitor CBC and LFTs frequently","May cause blood dyscrasias, including leukopenia and thrombocytopenia","Suicidal behavior and ideation have been reported","Use with caution in patients with renal impairment, as felbamate is renally excreted","May cause visual field defects (e.g., retinal abnormalities) with long-term use","Central nervous system effects include dizziness, ataxia, somnolence, and fatigue"]

Clinical Tips & Counseling

Drug interactions

Loading safety data…

FELBATOL

Clinical safety rating: caution

Comprehensive clinical and safety monograph for FELBATOL (FELBATOL).

How it works

What the body does with it

Metabolism	Felbamate is primarily metabolized in the liver via cytochrome P450 enzymes, including CYP3A4, CYP2E1, and CYP2C19. It also undergoes hydrolysis to inactive metabolites.
Excretion	Renal: 40-50% unchanged; Hepatic metabolism accounts for ~50% with glucuronidation and oxidation; minimal biliary/fecal excretion (<5%).
Half-life	20-23 hours; steady state reached within 3-5 days; may be prolonged in hepatic impairment.
Protein binding	20-30% primarily to albumin; low binding reduces displacement interactions.
Volume of Distribution	0.7 L/kg; indicates limited extravascular distribution consistent with low lipophilicity.
Bioavailability	Oral: ~90%; high and consistent absorption with minimal first-pass metabolism.
Onset of Action	Oral: 1-2 hours for therapeutic effect; IV administration not available.
Duration of Action	12-24 hours; sustained by high trough levels with twice-daily dosing.

Classification & Brands

Dosing & administration

1200-3600 mg/day orally in 3-4 divided doses; initial titration recommended.

Dosage form	SUSPENSION
Renal impairment	CrCl <50 mL/min: reduce dose by 50%; CrCl <30 mL/min: avoid use.
Liver impairment	Child-Pugh Class A: use 50% of usual dose; Class B or C: contraindicated.
Pediatric use	For Lennox-Gastaut syndrome (age 2-14 years): 15 mg/kg/day in 3-4 divided doses, increase weekly by 15 mg/kg/day to max 45 mg/kg/day.
Geriatric use	Start at lower end of dosing range; monitor renal function closely.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

Comprehensive clinical and safety monograph for FELBATOL (FELBATOL).

Breastfeeding	Present in breast milk; estimated relative infant dose 1.2% of maternal weight-adjusted dose. Milk-to-plasma ratio 0.3. Not recommended unless benefit outweighs risk; monitor infant for sedation, poor feeding, and withdrawal symptoms.
Teratogenic Risk	FDA Pregnancy Category C. First trimester: Increased risk of major congenital malformations, particularly orofacial clefts (odds ratio 5.05) and neural tube defects. Second/third trimester: Risk of neonatal hemorrhage due to vitamin K-dependent clotting factor inhibition; also associated with decreased IQ scores at age 6-7 years. Neonatal withdrawal syndrome possible.

Warnings & precautions

■ FDA Black Box Warning

Felbamate is associated with aplastic anemia and liver failure, which can be fatal. It should be used only in patients who fail alternative treatments and for whom the benefit outweighs the risk.