phenytoin

phenytoin

Indication

• Treatment of neonatal seizures which are refractory to maximal doses of PHENobarbital alone

Dosage Guidelines

Loading Dose: 15-20 mg/kg/dose IV

Maintenance dose: 2-4 mg/kg/dose IV/ORAL q12 hours (start 12 hours after loading dose)

Administration

• A 0.22 MICRON IN-LINE FILTER IS REQUIRED DUE TO THE POTENTIAL OF DRUG PRECIPITATION
• IV intermittent slow infusion.  Usual maximum recommended rate is 0.5-1 mg/kg/min
• To make 10 mL of a 5 mg/mL solution:
  1. Draw up 1 mL (50 mg) of phenytoin 50 mg/mL injection
  2. Dilute with 9 mL of normal saline to make a total volume of 10 mL

          (Final concentration 5 mg/mL)

• Diluted solution must be used within 1 hour of preparation.
• Not compatible with dextrose solutions.  Flush IV with normal saline before and after administration.
• Use peripheral IV if possible.  Avoid using PICC line to reduce the risk of phenytoin crystallization and line occlusion
• ORAL

Adverse Effects

• Following IV administration: hypotension, bradycardia, ventricular fibrillation, vasodilation, venous irritation, pain, thrombophlebitis, skin rash.
• GI side effects: vomiting, constipation
• May be seen with chronic use: hepatotoxicity, gingival hyperplasia, hyperglycemia and osteoporosis

Comments

• Monitor IV site closely. To avoid local tissue injury, use a 5 mg/mL solution of phenytoin, flush the IV catheter with 0.9% NaCl before and after phenytoin administration and avoid small hand, wrist or foot veins.
• Monitor for hypotension and arrythmias during IV administration
• Oral route has slow and variable absorption
• Maintain serum phenytoin concentrations between 40-80 micromol/L.  Draw level at least 2 hours after loading dose or 0 to 2 hours prior to the maintenance dose of Day 3 of maintenance.
• Peak effect: 30 minutes (IV), 4 to 7 hours (oral)
• Half-life 15 to 105 hours

Supplied As

• 50 mg/mL, 2 mL ampoule for IV use
• 25 mg/mL oral suspension