Recommended IV Antibiotic Regimen for Cellulitis
For adult patients with cellulitis requiring intravenous therapy, ceftriaxone 1-2g IV once daily is the recommended first-line treatment due to its proven efficacy, convenient once-daily dosing, and excellent safety profile. 1
Treatment Algorithm for IV Antibiotics in Cellulitis
First-Line Options:
- Ceftriaxone 1-2g IV once daily (preferred for most patients)
- Cefazolin 2g IV once daily plus probenecid 1g orally once daily (cost-effective alternative) 2
For MRSA Coverage (when indicated):
- Vancomycin 15-20 mg/kg IV every 12 hours (when MRSA is suspected)
- Daptomycin 4 mg/kg IV once daily (alternative for MRSA coverage) 3
When to Use IV Antibiotics
IV antibiotics are indicated for cellulitis in the following scenarios:
- Severe infection with systemic inflammatory response syndrome (SIRS)
- Altered mental status
- Hemodynamic instability
- Signs of deeper or necrotizing infection
- Failure of outpatient oral antibiotic therapy
- Severe immunocompromise 1
Duration of IV Therapy
- Standard duration: 5-7 days for uncomplicated cellulitis
- Consider transition to oral therapy when:
- Clinical improvement is demonstrated
- Patient is afebrile for 24-48 hours
- Erythema and induration are improving
- No signs of systemic toxicity 1
Monitoring Response
- Reassess within 48-72 hours to evaluate treatment response
- Consider hospitalization if no improvement within 24-48 hours of outpatient treatment
- Monitor for abscess formation (fluctuance, persistent fever despite antibiotics)
- Daily follow-up until clear improvement is noted 1
Special Considerations
MRSA Coverage
- MRSA coverage is generally unnecessary for typical cellulitis (successful treatment with β-lactams in 96% of cases)
- Consider MRSA coverage if:
- Purulent drainage
- History of penetrating trauma
- Previous MRSA infection
- High local prevalence of MRSA 1
Adjunctive Measures
- Elevation of the affected limb to promote drainage of edema and inflammatory substances
- Consider systemic corticosteroids in non-diabetic adults to reduce inflammation and hasten recovery 1
Evidence for Specific Regimens
- Cefazolin (2g IV) plus probenecid (1g orally) once daily has been shown to be equivalent to ceftriaxone (1g IV) once daily in a randomized controlled trial, with cure rates of 86% and 96% respectively 2
- Once-daily regimens increase treatment capacity and patient comfort compared to multiple daily dosing 4
- Macrolides/streptogramins have been found to be more effective than penicillin antibiotics in some studies 5
Prevention of Recurrence
For patients with recurrent cellulitis:
- Address underlying risk factors (lymphedema, tinea pedis, venous eczema)
- Consider prophylactic antibiotics for patients with 3-4 episodes per year 6
The choice of IV antibiotic should be guided by local antibiogram data whenever possible, as regional variations in pathogen susceptibility patterns can influence treatment success.