Cefazolin IV Dosing for an 8-Year-Old Child Weighing 29kg
For this 29 kg child, administer cefazolin 75 mg/kg every 8 hours intravenously, which equals approximately 725 mg (2,175 mg total daily dose) every 8 hours. 1
Standard Pediatric Dosing Framework
The FDA-approved pediatric dosing for cefazolin in children over 1 month of age is 75 mg/kg every 8 hours for most infections 2. This translates to:
- Dose per administration: 29 kg × 75 mg/kg = 2,175 mg per dose
- Frequency: Every 8 hours (three times daily)
- Total daily dose: 6,525 mg/day
However, the guideline from the Infectious Diseases Society of America specifies 75 mg/kg every 8 hours as the standard regimen 1, which I've calculated above.
Dosing Range Considerations
The FDA label provides flexibility in pediatric dosing based on infection severity 2:
- Mild to moderate infections: 25-50 mg/kg/day divided into 3-4 equal doses
- Severe infections: Up to 100 mg/kg/day (maximum 45 mg/lb/day)
For a 29 kg child:
- Mild infections: 725 mg every 8 hours (25 mg/kg/day range)
- Moderate to severe infections: 725-967 mg every 8 hours (75-100 mg/kg/day range)
Practical Administration
The most appropriate dosing for this child is 725 mg IV every 8 hours, which falls within the standard moderate-to-severe infection range and aligns with IDSA guidelines 1. This can be rounded to 750 mg every 8 hours for practical preparation, as this represents approximately 75 mg/kg/dose 2.
Reconstitution and Administration
For IV administration 2:
- Reconstitute 1 g vial with 2.5 mL Sterile Water for Injection (yields 330 mg/mL concentration)
- For direct IV bolus: Further dilute with approximately 5 mL Sterile Water for Injection and inject slowly over 3-5 minutes
- For intermittent infusion: Dilute reconstituted solution in 50-100 mL of compatible IV fluid (0.9% NaCl or 5% Dextrose)
Important Clinical Caveats
Renal function monitoring is essential 2. For children with normal renal function (creatinine clearance ≥55 mL/min), full doses can be administered. If renal impairment is present:
- Mild impairment (CrCl 70-40 mL/min): 60% of normal daily dose divided every 12 hours
- Moderate impairment (CrCl 40-20 mL/min): 25% of normal daily dose divided every 12 hours
- Severe impairment (CrCl 20-5 mL/min): 10% of normal daily dose every 24 hours
All reduced dosing requires an initial loading dose appropriate to infection severity 2.
Duration of Therapy
Treatment duration depends on the specific infection being treated 1, 2:
- Uncomplicated infections: 5-7 days
- Complicated infections or bacteremia: 10-14 days minimum
- Endocarditis: 6 weeks (per IDSA/AHA guidelines) 1
Common Pitfalls to Avoid
- Underdosing: Do not use the lower 25 mg/kg/day range for serious infections; this is reserved only for mild infections 2
- Inadequate frequency: Cefazolin requires every 8-hour dosing in children to maintain adequate serum concentrations; do not extend to every 12 hours unless renal impairment is present 1, 2
- Failure to adjust for renal function: Always assess renal function before initiating therapy and adjust accordingly 2