Phenytoin


Description

An anticonvulsant that is used in a wide variety of seizures. It is also an anti-arrhythmic and a muscle relaxant. The mechanism of therapeutic action is not clear, although several cellular actions have been described including effects on ion channe...

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Pharmacology

Indication

For the control of generalized tonic-clonic (grand mal) and complex partial (psychomotor, temporal l... Read more

Pharmacodynamic

Phenytoin is an antiepileptic drug used in the treatment of epilepsy. The primary site of action app... Read more

Mechanism of action

Phenytoin causes a voltage-dependent block of voltage gated sodium channels on the neuronal cell mem... Read more

Absorption

Bioavailability 70-100% oral, 24.4% rectal. Rapid rate of absorption with peak blood concentration e... Read more

Protein binding

Highly protein bound, 90%. There are reports indicating that a low content of albumin in the body ca... Read more

Volume of distribution

Information currently not available.

Clearance

Information currently not available.

Half life

22 hours (range of 7 to 42 hours)

Route of elimination

Most of the drug is excreted in the bile as inactive metabolites which are then reabsorbed from the... Read more

Toxicity

Oral, mouse: LD50 = 150 mg/kg; Oral, rat: LD50 = 1635 mg/kg. Symptoms of overd... Read more


Adverse Effects

Effect Regions Age Groups Incidences Evidence Type
Nystagmus US
  • Kind: experimental
    • Percent: 59%
  • Clinical Trial
    Somnolence US
  • Kind: experimental
    • Percent: 27%
  • Clinical Trial
    Dizziness US
  • Kind: experimental
    • Percent: 27%
  • Clinical Trial
    Ataxia US
  • Kind: experimental
    • Percent: 18%
  • Clinical Trial
    Nausea US
  • Kind: experimental
    • Percent: 14%
  • Clinical Trial
    Tremor US
  • Kind: experimental
    • Percent: 13%
  • Clinical Trial
    Somnolence US
  • Kind: experimental
    • Percent: 10%
  • Clinical Trial
    Hypesthesia US
  • Kind: experimental
    • Percent: 9%
  • Clinical Trial
    Tremor US
  • Kind: experimental
    • Percent: 9%
  • Clinical Trial
    Amblyopia US
  • Kind: experimental
    • Percent: 9%
  • Clinical Trial
    Tinnitus US
  • Kind: experimental
    • Percent: 9%
  • Clinical Trial
    Vomiting US
  • Kind: experimental
    • Percent: 9%
  • Clinical Trial
    Hypotension US
  • Kind: experimental
    • Percent: 9%
  • Clinical Trial
    Ataxia US
  • Kind: experimental
    • Percent: 8%
  • Clinical Trial
    Nystagmus US
  • Kind: experimental
    • Percent: 8%
  • Clinical Trial
    Accidental injury US
  • Kind: experimental
    • Percent: 7%
  • Clinical Trial
    Brain Edema US
  • Kind: experimental
    • Percent: 5%
  • Clinical Trial
    Pruritus US
  • Kind: experimental
    • Percent: 5%
  • Clinical Trial
    Incoordination US
  • Kind: experimental
    • Percent: 5%
  • Clinical Trial
    Ecchymosis US
  • Kind: experimental
    • Percent: 5%
  • Clinical Trial
    Headache US
  • Kind: experimental
    • Percent: 5%
  • Clinical Trial
    Dry Mouth US
  • Kind: experimental
    • Percent: 5%
  • Clinical Trial
    Headache US
  • Kind: experimental
    • Percent: 5%
  • Clinical Trial
    Vasodilatation US
  • Kind: experimental
    • Percent: 5%
  • Clinical Trial
    Stupor US
  • Kind: experimental
    • Percent: 5%
  • Clinical Trial
    Incoordination US
  • Kind: experimental
    • Percent: 5%
  • Clinical Trial
    Reflexes decreased US
  • Kind: experimental
    • Percent: 5%
  • Clinical Trial
    Asthenia US
  • Kind: experimental
    • Percent: 3%
  • Clinical Trial
    Paresthesia US
  • Kind: experimental
    • Percent: 3%
  • Clinical Trial
    Dizziness US
  • Kind: experimental
    • Percent: 3%
  • Clinical Trial
    Nausea US
    Varying Reports
    Sensory Peripheral Neuropathy US
    Varying Reports
    Asterixis US
    Varying Reports
    Dystonia US
    Varying Reports
    Chorea US
    Varying Reports
    Dyskinesia US
    Varying Reports
    Motor twitching US
    Varying Reports
    Transient nervousness US
    Varying Reports
    Allergic Reaction US
    Varying Reports
    Acute hepatic failure US
    Varying Reports
    Gingival Hyperplasia US
    Varying Reports
    Enlargement of the lips US
    Varying Reports
    Liver Damage US
    Varying Reports
    Toxic hepatitis US
    Varying Reports
    Constipation US
    Varying Reports
    Vomiting US
    Varying Reports
    Mental confusion US
    Varying Reports
    Insomnia US
    Varying Reports
    Slurred speech US
    Varying Reports
    Increased serum levels of glucose US
    Varying Reports

    Contraindications

    • Route:
      • Intravenous
    • Regions: US
    • Patient Conditions:
        • Name: Adams-Stokes Syndrome
        • Drugbank Id: DBCOND0000492
    • Route:
      • Intravenous
    • Regions: US
    • Patient Conditions:
        • Name: Third degree AV block
        • Drugbank Id: DBCOND0107810
    • Route:
      • Intravenous
    • Regions: US
    • Patient Conditions:
        • Name: Second degree AV block
        • Drugbank Id: DBCOND0095721
    • Route:
      • Intravenous
    • Regions: US
    • Patient Conditions:
        • Name: Sinoatrial Block
        • Drugbank Id: DBCOND0000489
    • Route:
      • Intravenous
    • Regions: US
    • Patient Conditions:
        • Name: Sinus Bradycardia
        • Drugbank Id: DBCOND0042990
    • Regions: US
    • Patient Conditions:
        • Name: Prior acute hepatotoxicity
        • Drugbank Id: DBCOND0107531
    • Regions: US
    • With Drugs:
        • Name: Delavirdine
        • Drugbank Id: DB00705

    Food Interactions

    • Avoid alcohol.
    • Do not take calcium, aluminum, magnesium or Iron supplements within 2 hours of taking this medication.
    • Take with food to increase bioavailability and reduce irritation.

    Interactions

    Type in a drug name to check for interaction with Phenytoin

    The serum concentration of Phenytoin can be decreased when it is combined with (6R)-Folinic acid.
    The serum concentration of Phenytoin can be decreased when it is combined with (6S)-5,6,7,8-tetrahydrofolate.
    The metabolism of (R)-warfarin can be increased when combined with Phenytoin.
    The metabolism of (S)-Warfarin can be increased when combined with Phenytoin.
    The therapeutic efficacy of Phenytoin can be decreased when used in combination with 2,5-Dimethoxy-4-ethylamphetamine.
    The therapeutic efficacy of Phenytoin can be decreased when used in combination with 2,5-Dimethoxy-4-ethylthioamphetamine.
    The serum concentration of 3-isobutyl-1-methyl-7H-xanthine can be decreased when it is combined with Phenytoin.
    The metabolism of 3,5-diiodothyropropionic acid can be increased when combined with Phenytoin.
    The therapeutic efficacy of Phenytoin can be decreased when used in combination with 4-Bromo-2,5-dimethoxyamphetamine.
    The metabolism of 4-hydroxycoumarin can be increased when combined with Phenytoin.
    The risk or severity of adverse effects can be increased when Phenytoin is combined with 4-Methoxyamphetamine.
    The metabolism of 5-androstenedione can be increased when combined with Phenytoin.
    The serum concentration of Phenytoin can be increased when it is combined with 5-fluorouridine.
    The risk or severity of adverse effects can be increased when Phenytoin is combined with 5-methoxy-N,N-dimethyltryptamine.
    The serum concentration of Phenytoin can be decreased when it is combined with 5-methyltetrahydrofolic acid.
    The metabolism of 6-O-benzylguanine can be increased when combined with Phenytoin.
    The serum concentration of 7-Deazaguanine can be decreased when it is combined with Phenytoin.
    The metabolism of 7-ethyl-10-hydroxycamptothecin can be increased when combined with Phenytoin.
    The risk or severity of adverse effects can be increased when Phenytoin is combined with 7-Nitroindazole.
    The risk or severity of adverse effects can be increased when Phenytoin is combined with 7,8-Dichloro-1,2,3,4-tetrahydroisoquinoline.

    References

    • 1 . Mallet L, Spinewine A, Huang A: The challenge of managing drug interactions in elderly people. Lancet. 2007 Jul 14;370(9582):185-191. doi: 10.1016/S0140-6736(07)61092-7. [PubMed: 17630042]
    • 2 . Link [Link]

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