Pharmacology · Antiseizure medicines
Felbamate !
A last-resort antiseizure medicine for severe epilepsy. It can cause aplastic anaemia and liver failure, so it is used only when the benefit justifies it.
Updated 2026-11-01
Mechanism of action
Felbamate blocks the NMDA type of glutamate receptor by acting at its strychnine-insensitive glycine site, reducing excitatory signalling. Its exact antiseizure mechanism is not fully known.
- Acts at the glycine site of the NMDA receptor
- NMDA-mediated excitation is reduced
- Neuronal hyperexcitability falls
- Severe seizures become less frequent
Pharmacokinetics
- Absorption
- Absorbed by mouth
- Elimination
- Partly by the kidneys; clearance falls and half-life lengthens in kidney disease
- Half-life
- About 20 to 23 hours
Indications
- Severe focal seizures in adults not controlled by other medicines Epilepsy and seizures →
- Seizures of Lennox-Gastaut syndrome in children, when other treatments fail
Adverse effects
Common
- Loss of appetite and weight loss
- Heartburn, vomiting, constipation and diarrhoea
- Difficulty sleeping and nervousness
- Drowsiness
Contraindications
- Hypersensitivity to felbamate or other carbamates
- History of any blood dyscrasia
- Liver dysfunction
Key interactions
- Phenytoin
- Felbamate raises phenytoin levels
- Valproate
- Felbamate raises valproate levels
- Carbamazepine
- Lower carbamazepine but higher carbamazepine epoxide levels
- Low-dose combined oral contraceptives
- Lower hormone levels
What is monitored
- Complete blood count before and during treatment
- Liver tests before and during treatment
- Signs of infection, bleeding, jaundice or dark urine
- Mood and suicidal thoughts
Administration and safety
- Given by mouth as tablets or suspension
- Used only after the patient or guardian has been informed of the risks, with written acknowledgement
- Withdrawn gradually: stopping suddenly can trigger seizures
Nursing care
- Confirm the risk acknowledgement has been signed before starting
- Teach to report fever, sore throat, bruising, bleeding or yellow skin at once
- Check that blood and liver tests are done on schedule
- Watch appetite and weight
Pregnancy and breastfeeding
Human data are limited; benefits and risks are weighed with specialist care.
Test yourself
Think of the answer, then tap the question to see it.
What are the two boxed warnings of felbamate?
Aplastic anaemia and hepatic failure, which is why it is reserved for severe epilepsy when the benefit justifies the risk.
At which receptor site does felbamate act?
The strychnine-insensitive glycine site of the NMDA glutamate receptor.
What does felbamate do to phenytoin and valproate levels?
It raises both, so their doses are often reduced when felbamate is started.
Related drugs
Related conditions
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Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: Felbamate: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2020); DailyMed - FELBAMATE tablet (DailyMed (U.S. National Library of Medicine), 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 20 (McGraw Hill, 2023).
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Representative model, for educational purposes only.