Cefazolin Dosing for Open Finger Fracture
For this 9-year-old male weighing 63 pounds (28.6 kg) with an open finger fracture, administer cefazolin 33 mg/kg/dose (approximately 950 mg) intravenously every 8 hours, with the first dose given immediately. 1
Weight-Based Calculation
- The patient weighs 63 pounds, which equals 28.6 kg 1
- The recommended dose is 33 mg/kg/dose every 8 hours, yielding approximately 950 mg per dose (28.6 kg × 33 mg/kg = 943 mg) 1, 2
- This falls well within the maximum pediatric dosing of 150 mg/kg/day (which would be 4,290 mg/day for this patient), divided into three doses 1, 3
Administration Protocol
- Administer the first dose intravenously as soon as possible after injury, ideally within 1 hour 1
- Continue dosing every 8 hours until 24-48 hours post-wound closure 1
- For IV administration, reconstitute and further dilute the dose, then inject slowly over 3 to 5 minutes 4
Rationale for This Regimen
- Cefazolin monotherapy is appropriate for mild to moderate open fractures because it provides excellent coverage against methicillin-susceptible Staphylococcus aureus (MSSA), the primary pathogen in open fractures 1, 2
- Open finger fractures typically represent Gustilo-Anderson Type I or II injuries, where cefazolin monotherapy is the standard of care 1
- Recent evidence confirms that cefazolin achieves sustained concentrations above the MIC for S. aureus at open fracture sites, even in traumatized tissue 5
Duration of Therapy
- Limit antibiotic prophylaxis to 24-48 hours post-wound closure 1
- Do not extend therapy unnecessarily, as short-course treatment is appropriate for uncomplicated open fractures and prevents antimicrobial resistance 1, 2
Important Clinical Considerations
- Administer preoperatively if surgical repair is planned, ideally 30-60 minutes before incision 2
- The FDA-approved pediatric dosing range of 25-50 mg/kg/day for mild-moderate infections 4 is lower than the IDSA-recommended 33 mg/kg/dose every 8 hours (which equals 99 mg/kg/day) 1, but guideline recommendations should take precedence for open fractures given the infection risk
- For contaminated wounds or if MRSA is suspected, consider adding vancomycin or switching to clindamycin 2
Common Pitfalls to Avoid
- Do not underdose based on older weight-based recommendations (25-50 mg/kg/day); open fractures require the higher 33 mg/kg/dose every 8 hours 1
- Do not delay the first dose—timing is critical, with administration ideally within 1 hour of injury 1
- Do not continue antibiotics beyond 24-48 hours post-closure unless there are signs of established infection 1