Cefazolin Dosage Calculation for a 20kg Child
For a 20kg child requiring 50 mg/kg/day of cefazolin, the total daily dose is 1000 mg (1 gram), which should be divided into 3 or 4 equal doses throughout the day.
Dosage Calculation
The calculation is straightforward:
- 20 kg × 50 mg/kg/day = 1000 mg/day (1 gram/day) 1
Dosing Schedule Options
According to FDA labeling and IDSA guidelines, this total daily dose should be divided as follows 2, 1:
Option 1: Three Times Daily (Every 8 Hours)
- Approximately 330 mg per dose, given every 8 hours 1
- This provides consistent coverage throughout the day
Option 2: Four Times Daily (Every 6 Hours)
- 250 mg per dose, given every 6 hours 1
- This may provide more stable serum concentrations but requires more frequent administration
Clinical Context and Dosing Range
The FDA-approved pediatric dosing for cefazolin ranges from 25-50 mg/kg/day for mild to moderately severe infections, divided into 3 or 4 equal doses 1. Your specified dose of 50 mg/kg/day represents the upper end of the standard dosing range, which is appropriate for:
- More severe infections 1
- Infections requiring robust gram-positive coverage 2
- Surgical prophylaxis in certain contexts 1
For severe infections, the FDA label allows escalation up to 100 mg/kg/day (which would be 2000 mg/day for this 20kg child), though this exceeds your specified dose 1.
Administration Considerations
Intravenous administration is standard for cefazolin in pediatric patients 1:
- Can be given as direct IV bolus over 3-5 minutes after appropriate dilution 1
- Can be given as intermittent infusion diluted in 50-100 mL of compatible solution 1
Important Caveats
- This dosing assumes normal renal function 1. If creatinine clearance is reduced, dosage adjustments are necessary 1.
- Cefazolin is not recommended for neonates or premature infants due to lack of safety data 1.
- For a 20kg child with mild to moderate renal impairment (creatinine clearance 70-40 mL/min), reduce to 60% of the normal daily dose given every 12 hours 1.