What are the appropriate IV (intravenous) or PO (per oral) medications for possible cellulitis?

Medication Selection for Possible Cellulitis

First-Line Treatment Recommendations

For possible cellulitis, empiric therapy should be based on whether the infection is purulent or non-purulent, with oral beta-lactams for non-purulent cellulitis and MRSA coverage for purulent cellulitis. 1, 2

Non-Purulent Cellulitis (No Drainage/Exudate/Abscess)

• First-line (outpatient):

  • Beta-lactam antibiotics (target streptococci)
    • Cephalexin 500 mg PO four times daily
    • Amoxicillin 500 mg PO three times daily
  • Duration: 5-10 days, based on clinical response

• If no response to beta-lactams or systemic toxicity present:

  • Add MRSA coverage

Purulent Cellulitis (With Drainage/Exudate)

• First-line (outpatient):

  • TMP-SMX (Trimethoprim-sulfamethoxazole) 1-2 DS tablets PO twice daily 1, 3
  • Clindamycin 300-450 mg PO three times daily 1
  • Doxycycline or minocycline 100 mg PO twice daily 1
  • Linezolid 600 mg PO twice daily 1, 4

• If coverage for both streptococci and MRSA desired:

  • Clindamycin alone 1
  • TMP-SMX or tetracycline plus amoxicillin 1
  • Linezolid alone 1, 4

Hospitalized Patients with Complicated Cellulitis

For patients requiring hospitalization (deeper infections, surgical/traumatic wounds, major abscesses):

• First-line IV options:
  • Vancomycin IV (15-20 mg/kg/dose every 12 hours) 1, 2
  • Linezolid 600 mg IV/PO twice daily 1, 4
  • Daptomycin 4 mg/kg IV once daily 1
  • Telavancin 10 mg/kg IV once daily 1
  • Clindamycin 600 mg IV three times daily 1

Special Considerations

Risk Factors for Treatment Failure

• Chronic venous disease (4.4 times higher risk of failure) 5
• Advanced age 6
• Elevated C-reactive protein levels 6
• Diabetes mellitus 6
• Concurrent bloodstream infection 6
• Obesity 3
• Moderate-to-severe cellulitis 3

Pediatric Considerations

• Children <8 years: Avoid tetracyclines 1
• For hospitalized children: Vancomycin IV or clindamycin 10-13 mg/kg/dose IV every 6-8 hours 1
• Linezolid dosing for children <12 years: 10 mg/kg/dose PO/IV every 8 hours 1

Treatment Duration

• Typical duration: 5-10 days for uncomplicated cellulitis 1, 2
• Extend treatment for:
  • Slow clinical response
  • Severe initial infection
  • Immunocompromised patients
  • Presence of complicating factors (diabetes, chronic venous disease)

Monitoring Response

• Daily follow-up until definite improvement is noted 2
• Signs of improvement:
  • Decreased erythema, swelling, and pain
  • No new lesions in preceding 48 hours
  • Resolution of systemic symptoms (fever, chills)

Common Pitfalls to Avoid

1. Failing to obtain cultures: Always obtain cultures from abscesses and purulent drainage before starting antibiotics 1
2. Inadequate MRSA coverage: In areas with high MRSA prevalence, empiric MRSA coverage significantly improves outcomes (91% vs 74% success rate) 3
3. Missing deeper infections: Watch for pain disproportionate to physical findings, which may indicate deeper infection 2
4. Overlooking risk factors for recurrence: Address underlying conditions like edema, obesity, eczema, and venous insufficiency 2
5. Inadequate follow-up: Hospitalize patients with no improvement within 24-48 hours of outpatient therapy 2

Remember that incision and drainage is the primary treatment for abscessed cellulitis, with antibiotics added for complex cases 2.