What is the recommended treatment for cellulitis?

Treatment of Cellulitis

For uncomplicated cellulitis, first-line treatment should be oral antibiotics targeting Streptococcus and methicillin-sensitive Staphylococcus aureus (MSSA), such as cephalexin 500 mg 3-4 times daily or dicloxacillin for 5-6 days. 1

Classification and Initial Assessment

When evaluating cellulitis, consider:

• Severity (mild, moderate, severe)
• Presence of purulence
• Patient risk factors for MRSA
• Systemic symptoms

Treatment Algorithm

Mild to Moderate Non-Purulent Cellulitis

• First-line options 1, 2:

  • Cephalexin 500 mg 3-4 times daily for 5-6 days
  • Dicloxacillin 500 mg four times daily for 5-6 days

• Alternative options (if penicillin allergic) 1:

  • Clindamycin 300-450 mg orally three times daily for 5-6 days
  • Amoxicillin-clavulanate 875/125 mg twice daily for 5-6 days

Severe or Complicated Cellulitis

• Inpatient treatment recommended 1:
  • Vancomycin 15 mg/kg IV every 12 hours or linezolid 600 mg IV/PO every 12 hours
  • For suspected polymicrobial infections: add coverage with ceftriaxone and metronidazole
  • For suspected necrotizing fasciitis: broad-spectrum coverage with vancomycin or linezolid plus piperacillin-tazobactam or a carbapenem

Special Considerations

MRSA Risk Factors

Consider MRSA coverage for patients with 1, 2:

• Prior MRSA exposure
• Athletes
• Children
• Men who have sex with men
• Prisoners
• Military recruits
• Residents of long-term care facilities
• Intravenous drug users

Pediatric Patients

• Avoid doxycycline in children under 8 years due to risk of dental staining 1
• Dosing should be weight-based

Pregnant Patients

• Avoid doxycycline 1
• Cephalexin is generally considered safe

Diagnostic Considerations

• Cellulitis is primarily a clinical diagnosis 2, 3
• Obtain cultures when possible, especially in severe cases 1:
  • Blood cultures before starting antibiotics
  • Culture any wound drainage or abscess material

Treatment Duration and Follow-up

• Standard treatment duration: 5-6 days 1, 2
• Extend treatment if symptoms have not improved
• For bacteremia: 10-14 days (uncomplicated) 1
• For endocarditis/osteomyelitis: 4-6 weeks 1
• Follow up within 2-3 days to ensure improvement 1
• If no improvement after 72 hours, reassess diagnosis and consider changing antibiotics 1, 2

Common Pitfalls and Caveats

1. Misdiagnosis: Many conditions mimic cellulitis including venous stasis dermatitis, contact dermatitis, eczema, and lymphedema 3. Careful assessment is crucial.

2. Unnecessary MRSA coverage: Despite rising rates of community-acquired MRSA, coverage for non-purulent cellulitis is generally not recommended unless specific risk factors are present 3.

3. Failure to recognize necrotizing fasciitis: This is a surgical emergency requiring immediate intervention. Watch for disproportionate pain, rapid progression, skin necrosis, or systemic toxicity 1.

4. Inadequate follow-up: Patients should be reassessed within 2-3 days to ensure appropriate response to therapy 1.

5. Overlooking predisposing factors: Addressing underlying conditions (lymphedema, venous insufficiency, tinea pedis) is essential to prevent recurrence 1, 2.