Mephenytoin
Mephenytoin is an anticonvulsant medication belonging to the hydantoin class, historically used for the treatment of various types of epileptic seizures. It works by stabilizing neuronal membranes and reducing seizure activity in the brain. Due to its significant side effect profile, including potentially severe skin reactions and blood disorders, it has been largely replaced by safer alternatives in modern clinical practice.
Mephenytoin is an older antiepileptic drug used to control seizures by stabilizing neuronal activity, though it has been largely superseded by safer medications in contemporary practice.
Key facts at a glance
- ATC
- N03AB04
- RxNorm
- 6757
- Generic
- Mephenytoin
- Class
- atc-n03
- Brands
- —
- Availability
- rx
- Lactation
- unknown
- Routes
- oral
- Forms
- tablet
- Regions
- US, EU, CN, JP
- Monitoring
- —
This page is for informational purposes only.
Do not use this information to diagnose yourself or to replace a physician's advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication. If you believe you are experiencing a medical emergency, call your local emergency number immediately.
Mephenytoin was primarily used to treat focal (partial) seizures and generalized tonic-clonic seizures in patients with epilepsy who did not respond adequately to other treatments. It was considered particularly useful in cases where other anticonvulsants were ineffective or not tolerated.
As a hydantoin derivative, mephenytoin works by blocking voltage-gated sodium channels in neurons, which stabilizes neuronal membranes and prevents the repetitive firing of action potentials that leads to seizure activity. This action reduces the spread of seizure activity in the brain.
This medication carries significant risks including severe dermatological reactions (such as Stevens-Johnson syndrome), blood dyscrasias, and liver toxicity requiring regular monitoring. Due to these safety concerns and the availability of safer alternatives, mephenytoin is rarely used in modern practice. It requires careful dosing and therapeutic drug monitoring.
Official drug label
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This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.
This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.
If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.
Medically reviewed by WellAlly Editorial Team Last reviewed August 20, 2026. · Read our editorial policy