What is the recommended loading dose of Dilantin (Phenytoin) for an 11kg child?

Phenytoin (Dilantin) Loading Dose for an 11kg Child

For an 11kg child requiring phenytoin loading, administer 220 mg (20 mg/kg) intravenously at a rate not exceeding 11 mg/minute (1 mg/kg/min), which will take approximately 20 minutes to infuse. 1, 2

Dosing Calculation

• Loading dose: 15-20 mg/kg IV 1, 2

  • For this 11kg child: 11 kg × 20 mg/kg = 220 mg total dose
  • This dose typically produces serum concentrations within the therapeutic range of 10-20 mcg/mL 1, 2

• Maximum infusion rate: 1-3 mg/kg/min OR 50 mg/min, whichever is slower 1, 2

  • For this 11kg child: 11 kg × 1 mg/kg/min = 11 mg/min maximum rate
  • At this rate, the 220 mg dose will take approximately 20 minutes to administer 1

Critical Administration Requirements

Monitoring During Infusion

• Continuous ECG monitoring is essential throughout the infusion 1, 2
• Continuous blood pressure monitoring is required 1, 2
• Observe for respiratory depression - be prepared to provide respiratory support 1
• Monitor heart rate closely - reduce infusion rate if heart rate decreases by 10 beats per minute 1

Preparation and Dilution

• Dilute phenytoin in normal saline only - never use glucose-containing solutions as phenytoin will precipitate 1
• Final concentration should be no less than 5 mg/mL when diluted 2
• Flush IV catheter with sterile saline after injection to avoid local venous irritation 2

Important Clinical Considerations

Cardiovascular Risks

• Phenytoin can cause hypotension and arrhythmias, especially with rapid infusion 1, 2
• The slow infusion rate (1 mg/kg/min) is mandated to minimize these cardiovascular adverse reactions 2

Respiratory Precautions

• Increased risk of apnea when phenytoin is combined with other sedative agents (particularly benzodiazepines) 1
• Have airway management equipment immediately available 1

Alternative Consideration

• Fosphenytoin is preferred when available because it has a lower risk of adverse cardiac effects and can be administered more rapidly 1
• Fosphenytoin dosing is given in phenytoin equivalents (PE): 15-20 PE/kg at 1-3 PE/kg/min 1

Follow-Up Dosing

After the loading dose, maintenance therapy should begin:

• Maintenance dose: Typically 5-8 mg/kg/day divided every 12 hours 2
• For this 11kg child: approximately 55-88 mg/day divided into two doses
• Serum level monitoring is essential to guide subsequent dosing adjustments 1, 2

Common Pitfalls to Avoid

• Never exceed the 1 mg/kg/min infusion rate in pediatric patients, even though 50 mg/min is safe in adults - this child's maximum rate is only 11 mg/min 1, 2
• Do not use intramuscular administration for acute seizure management as peak levels may take up to 24 hours to achieve 2
• Avoid mixing with dextrose solutions - this will cause immediate precipitation and loss of drug 1
• Do not underdose - neonates require 10 mg/kg, but children require the full 15-20 mg/kg loading dose 1, 2