Neonatal Drug Therapy Manual

Phenytoin

Disclaimer: Official controlled document is the CHEO and Ottawa Hospital online copy. It is the responsibility of user to ensure that any paper copy version is the same as the online version before use.

Updated July 2, 2026 - 3:05pm

Alternate Name(s): 
Dilantin
Classification: 
Anticonvulsant
Original Date: 
March 1992
Revised Date: 
June 2026
Indications: 
  • Treatment of Phenobarbital resistant seizures

  • To note: FOSphenytoin IV is preferred over phenytoin IV at CHEO, when available. 

Administration: 
  • IV intermittent infusion:
    • Flush IV lines with 0.9% NaCl before and after administration
    • Infuse into a large vein through a large gauge needle or IV catheter.  DO NOT use in PICC lines. Will block line.
    • Use an in-line 0.22 micron filter (TOH: Non-DEHP Extension set with 0.22 micron filter Inventory No. 120081)
  • Loading dose:  IV over 20 minutes
  • Maintenance dose: IV over 20-30 minutes
  • PO
Dosage: 
  • Loading dose: 20 mg/kg IV/PO
  • Maintenance dose: 5-8 mg/kg/day IV/PO divided BID

*Start at lower end of dosing range and titrate upwards based on efficacy/side effects

Side Effects: 
  • CNS: drowsiness, seizures with high levels
  • CVS: bradycardia, hypotension, arrhythmias
  • Endocrine and metabolic: hyperglycemia
  • Local: tissue inflammation and necrosis if extravasation
Parameters to Monitor: 
  • Observe IV site for extravasation
  • BP, HR with IV administration
  • Therapeutic drug levels: 40-80 micromol/L
    • Usual sampling time:
      •  After load: 1 hour post load
      • Maintenance: trough level (0-60 minutes before next dose) on day 3
Reconstitution and Stability: 

IV Intermittent Infusion:

  • Phenytoin 50 mg/mL
    • Take 2 mL (100 mg) and add to 18 mL 0.9% NaCl
    • Final concentration: 5 mg/mL

TOH:

  • Level 2 Hazardous Drug: consult the applicable corporate and nursing policies for drug handling, administration, and disposal
Compatibility: 

- Solutions Compatible: 0.9% NaCl only

Incompatible: do not mix with other drugs

References: 

-Taketomo CK, Hodding JH, Kraus DM. Pediatric Dosage Handbook 22ndEdition. Hudson: Lexi-Comp Inc.; 2015

-NIOSH List of Hazardous Drugs in Healthcare Settings, 2024. DHHS (NIOSH) Publication Number 2025-103, December 2024

 

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