#EMconf: Phenytoin: Friend or Foe?

  • Phenytoin (Dilantin) is a second line therapy for the actively seizing patient 
    -Use only if Fosphenytoin (Cerebyx) is not available
    -First line: Lorazepam IV, Diazepam IV, Midazolam IM
  • Dose → 20 mg/kg IV Rate
    - 1 mg/kg/min
    -Max rate of 50 mg/min
    -Geriatrics → 50 mg over 2-3 minutes
  • Contraindications:
    -Pregnancy (Category D)
    -Sinus Bradycardia AV Block - 2nd or 3rd degree
  • Feared Complication: If administered too quickly, can lead to fatal hypotension and cardiotoxicity


  • Fosphenytoin (Cerebyx)
    -Prodrug of phenytoin
    -Dosed as Phenytoin Equivalents (PE) Dose → 20 PE/kg IV Rate → 150 PE/min


Take Home Points
-Phenytoin IV is a good second line agent for the actively seizing patient if benzodiazepines fail, but must be administered slowly (no faster than 50mg/min) due to risk of fatal hypotension and cardiac toxicity. 


-If you have Fosphenytoin available, use it! It is safer and can be administered faster than Phenytoin.


Glauser, T., Shinnar, S., Gloss, D., Alldredge, B., Arya, R., Bainbridge, J., & ... Treiman, D. M. (2016). Evidence-Based Guideline: Treatment of Convulsive Status Epilepticus in Children and Adults: Report of the Guideline Committee of the American Epilepsy Society. Epilepsy Currents, 16(1), 48-61.