What is the recommended treatment for inpatient cellulitis?

Inpatient Treatment for Cellulitis

For inpatient treatment of cellulitis, beta-lactam antibiotics such as cefazolin or oxacillin are recommended as first-line therapy, with a 5-day course being as effective as a 10-day course if clinical improvement occurs. 1, 2

First-Line Treatment Options

Non-purulent Cellulitis (Most Common)

• First-line IV therapy:
  • Cefazolin: 1-2g IV every 8 hours
  • Oxacillin: 1-2g IV every 4-6 hours
  • Duration: 5 days initially, with extension if no improvement 1, 2

When to Consider MRSA Coverage

MRSA is an unusual cause of typical cellulitis. A study demonstrated that treatment with beta-lactams was successful in 96% of patients, suggesting MRSA coverage is usually unnecessary 1. However, MRSA coverage should be considered in specific situations:

• Cellulitis associated with:
  • Penetrating trauma
  • Illicit drug use
  • Purulent drainage
  • Concurrent evidence of MRSA infection elsewhere
  • Failure to respond to beta-lactam therapy within 48-72 hours

MRSA Coverage Options

• IV options:
  • Vancomycin: 15-20 mg/kg IV every 8-12 hours
  • Daptomycin: 4-6 mg/kg IV daily
  • Linezolid: 600 mg IV every 12 hours
  • Telavancin: 10 mg/kg IV once daily 1, 2

Assessment and Monitoring

• Reassess within 48-72 hours of initiating therapy
• If no improvement or worsening occurs:
  1. Consider changing to MRSA-active therapy
  2. Reassess diagnosis
  3. Evaluate for abscess formation that may require drainage 2

Blood Cultures and Diagnostic Testing

Blood cultures should be obtained for patients with:

• Malignancy
• Severe systemic features (high fever, hypotension)
• Unusual predisposing factors (immersion injury, animal bites)
• Neutropenia
• Severe cell-mediated immunodeficiency 1

Adjunctive Measures

• Elevation of the affected area to promote gravity drainage of edema and inflammatory substances 1, 2
• Systemic corticosteroids (e.g., prednisone 40 mg daily for 7 days) could be considered in non-diabetic adult patients 1
• Address predisposing conditions such as tinea pedis, trauma, or venous eczema 1, 2

Transition to Oral Therapy

When clinical improvement occurs, transition to oral therapy with:

• Cephalexin: 500 mg orally 4 times daily
• Dicloxacillin: 500 mg orally 4 times daily
• Amoxicillin-clavulanate: 875/125 mg orally twice daily
• For penicillin-allergic patients: Clindamycin 300-450 mg orally 3 times daily 2

Common Pitfalls to Avoid

1. Misdiagnosis: Conditions such as venous stasis dermatitis, contact dermatitis, and lymphedema can mimic cellulitis 2, 3
2. Unnecessary MRSA coverage: For typical non-purulent cellulitis, beta-lactam monotherapy is recommended 1, 3
3. Inadequate treatment duration: Premature discontinuation of antibiotics can lead to treatment failure 2
4. Failure to drain abscesses: Antibiotics alone are insufficient for purulent collections 2
5. Overlooking predisposing factors: Addressing underlying conditions is crucial for preventing recurrence 1, 2

Cellulitis is a common infection with more than 650,000 admissions per year in the United States 4. While the majority of cases are nonculturable, when organisms are identified, they are most commonly beta-hemolytic Streptococcus and Staphylococcus aureus 4. The evidence strongly supports that for most inpatient cases, beta-lactam antibiotics targeting these organisms are effective first-line therapy.