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Phenytoin Sodium (PHENYTOIN)
Phenytoin Sodium works by stabilizing the threshold against hyperexcitability caused by excessive stimulation.
Phenytoin Sodium, also known as PHENYTOIN, is an anti-epileptic agent developed by PARKE DAVIS and currently owned by Viatris. It targets the sodium channel protein type 2 subunit alpha and is used to treat various seizure disorders, including epilepsy and Lennox-Gastaut syndrome. Phenytoin Sodium has been FDA-approved since 1953 and is available as a generic medication. It has a half-life of 16.8 hours and a bioavailability of 90%. The medication is off-patent, with multiple generic manufacturers.
At a glance
| Generic name | PHENYTOIN |
|---|---|
| Sponsor | Viatris |
| Drug class | Anti-epileptic Agent |
| Target | Sodium channel protein type 2 subunit alpha |
| Modality | Small molecule |
| Therapeutic area | Neuroscience |
| Phase | FDA-approved |
| First approval | 1953 |
Mechanism of action
Mechanism of Action. Phenytoin is an antiepileptic drug which can be useful in the treatment of epilepsy. The primary site of action appears to be the where spread of seizure activity is inhibited. Possibly by promoting sodium efflux from neurons, phenytoin tends to the threshold against hyperexcitability caused by excessive stimulation or environmental changes capable of reducing membrane sodium gradient. This includes the reduction of post tetanic potentiation at synapses. Loss of post tetanic potentiation prevents cortical seizure foci from detonating adjacent cortical areas. Phenytoin reduces the maximal activity of brain stem centers responsible for the tonic phase of tonic-clonic (grand mal) seizures. motor cortex stabilize.
Approved indications
- Bipolar disorder in remission
- Epilepsy
- Epilepsy characterized by intractable complex partial seizures
- Lennox-Gastaut syndrome
- Localization-related epilepsy
- Motor cortex epilepsy
- Prevention of Seizures following Cranial Trauma or Surgery
- Seizures in Neurosurgery
- Simple partial seizure
- Status epilepticus
- Tonic-clonic epilepsy
- Tonic-clonic seizure
Boxed warnings
- WARNING: CARDIOVASCULAR RISK ASSOCIATED WITH RAPID INFUSION The rate of intravenous Phenytoin Sodium Injection administration should not exceed 50 mg per minute in adults and 1 to 3 mg/kg/min (or 50 mg per minute, whichever is slower) in pediatric patients because of the risk of severe hypotension and cardiac arrhythmias. Careful cardiac monitoring is needed during and after administering intravenous Phenytoin Sodium Injection. Although the risk of cardiovascular toxicity increases with infusion rates above the recommended infusion rate, these events have also been reported at or below the recommended infusion rate. Reduction in rate of administration or discontinuation of dosing may be needed [see Dosage and Administration (2.1) and Warnings and Precautions (5.1) ] . W ARN ING: CARDIOVASCULAR RISK ASSOCIATED WITH RAPID INFUSION S ee full prescribing information for complete boxed warning . The rate of intravenous Phenytoin Sodium Injection administration should not exceed 50 mg per minute in adults and 1 to 3 mg/kg/min (or 50 mg per minute, whichever is slower) in pediatric patients because of the risk of severe hypotension and cardiac arrhythmias. Careful cardiac monitoring is needed during and after administering intravenous Phenytoin Sodium Injection. Reduction in rate of administration or discontinuation of dosing may be needed ( 2.1 , 5.1 ).
Common side effects
- Nystagmus
- Ataxia
- Slurred speech
- Decreased coordination
- Mental confusion
- Dizziness
- Insomnia
- Transient nervousness
- Motor twitchings
- Headaches
- Nausea
- Vomiting
Drug interactions
- CYP2B6 Substrates
- CYP2C19 Substrates
- CYP2C8 Substrates
- CYP2C9 Substrates
- CYP3A4 Substrates
- P-glycoprotein Substrates
- aripiprazole
- fluorouracil
- metyrapone
- mexiletine
- quetiapine
- quinestrol
Key clinical trials
- A Study to Evaluate VH4524184 Tablet Absorption, Effects of Food, and Interactions With Other Drugs in Healthy Adults (PHASE1)
- A Study of the Effect of Itraconazole and Phenytoin on Calderasib (MK-1084) in Healthy Adults (MK-1084-008) (PHASE1)
- Levetiracetam Versus Phenobarbitone for the Treatment of Neonatal Seizures in a Tertiary Care Hospital. (NA)
- Effect of Phenytoin or Itraconazole on How BGB-16673 is Absorbed and Removed From the Body in Healthy Participants (PHASE1)
- Population Pharmacokinetics of Antiepileptic in Pediatrics
- Antiseizure Medication in Seizure Networks at Early Acute Brain Injury (PHASE4)
- Drug-Drug Interaction Study of Casdatifan in Healthy Adult Participants (ARC-29) (PHASE1)
- Early Post-Traumatic Seizures Prevention Trial (E-PTS Trial) (PHASE4)
Primary sources
Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.
| Source | Used for |
|---|---|
| FDA label | Mechanism, indications, dosing, boxed warnings, drug interactions |
| ClinicalTrials.gov | Trial enrolment, design, endpoints, results |
Competitive intelligence
For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:
- Phenytoin Sodium CI brief — competitive landscape report
- Phenytoin Sodium updates RSS · CI watch RSS
- Viatris portfolio CI