What is the recommended dosage of cefazolin for treating cellulitis?

Recommended Cefazolin Dosage for Cellulitis

For adults with cellulitis, the recommended dosage of cefazolin is 1 gram intravenously every 8 hours. 1

Adult Dosing

Standard Inpatient Dosing

• 1 gram IV every 8 hours for typical non-purulent cellulitis 1, 2
• Duration: 5 days, extended if infection has not improved within this period 1

Alternative Dosing Regimens

• For severe infections: Up to 2 grams IV every 8 hours 2
• For outpatient therapy options:
  • 2 grams IV once daily plus probenecid 1 gram orally (equivalent efficacy to ceftriaxone for moderate-to-severe cellulitis) 3
  • 2 grams IV twice daily (for home-based treatment programs) 4

Pediatric Dosing

• Children >1 month of age: 33 mg/kg/dose IV every 8 hours 1
• Total daily dosage: 25-50 mg/kg/day divided into 3 or 4 equal doses for most mild to moderately severe infections 2
• For severe infections: Up to 100 mg/kg/day 2

Dosage Adjustment for Renal Impairment

• CrCl ≥55 mL/min: No adjustment needed
• CrCl 35-54 mL/min: Standard dose every 8 hours
• CrCl 11-34 mL/min: Half the usual dose every 12 hours
• CrCl ≤10 mL/min: Half the usual dose every 18-24 hours 2

Clinical Decision Making Algorithm

1. Assess severity of cellulitis:

   • Mild (no systemic signs): Consider oral antibiotics active against streptococci
   • Moderate (systemic signs): Cefazolin 1g IV q8h
   • Severe (SIRS, altered mental status, hemodynamic instability): Consider broader coverage

2. Consider risk factors for MRSA:

   • If present (penetrating trauma, prior MRSA infection, injection drug use, SIRS): Add vancomycin or another MRSA-active agent
   • If absent: Cefazolin monotherapy is appropriate

3. Determine treatment setting:

   • Outpatient: Consider once-daily cefazolin 2g IV with probenecid 1g PO if appropriate
   • Inpatient: Standard cefazolin 1g IV q8h

Important Considerations

• Blood cultures are not routinely recommended for typical cellulitis but should be considered in immunocompromised patients, those with malignancy, or severe infections 1
• Elevation of the affected area and treatment of predisposing factors (edema, underlying skin disorders) are important adjuncts to antibiotic therapy 1
• For lower extremity cellulitis, examine interdigital toe spaces to identify and treat potential sources of infection 1
• Patients with chronic venous disease have higher failure rates with once-daily cefazolin plus probenecid regimens (53% vs 18%) and should be monitored closely 5

Pitfalls to Avoid

• Failure to extend treatment duration if clinical improvement is not observed after 5 days
• Overlooking underlying predisposing conditions that may lead to treatment failure or recurrence
• Not adjusting dosage in patients with renal impairment
• Missing signs of deeper or necrotizing infection that would require surgical consultation
• Unnecessary use of broader-spectrum antibiotics when cefazolin would be effective

Cefazolin remains a highly effective first-line agent for non-purulent cellulitis caused by susceptible streptococci and staphylococci, with multiple dosing strategies available to accommodate different clinical scenarios and treatment settings.