What are the recommended antibiotics for treating cellulitis?

Recommended Antibiotics for Cellulitis

For non-purulent cellulitis, first-line treatment should be a 5-6 day course of antibiotics active against streptococci, specifically cephalexin (500mg orally 4 times daily), a penicillin, or clindamycin for penicillin-allergic patients. 1

First-Line Antibiotic Options

Standard Cases (Targeting Streptococci)

• First choice oral options:

  • Cephalexin 500mg orally 4 times daily 1
  • Penicillin VK 1
  • Dicloxacillin 1

• For penicillin-allergic patients:

  • Clindamycin 1

• First choice IV options (if needed):

  • Cefazolin 1-2g IV every 8 hours 1

Duration of Therapy

• 5-6 days is sufficient for uncomplicated cellulitis in patients who can self-monitor and have close follow-up 2, 1
• Evidence from multiple studies supports shorter courses:
  • The DANCE trial showed similar cure rates between 6-day and 12-day courses of flucloxacillin 2
  • A randomized controlled trial demonstrated that 5 days of levofloxacin was as effective as 10 days for uncomplicated cellulitis 3

Special Considerations

When to Consider MRSA Coverage

Add coverage for MRSA when any of these risk factors are present:

• Penetrating trauma 1
• Evidence of MRSA infection elsewhere 2, 1
• Nasal colonization with MRSA 2, 1
• Injection drug use 2, 1
• Systemic inflammatory response syndrome 2, 1
• Purulent drainage 1

MRSA Coverage Options

• Oral options:

  • Trimethoprim-sulfamethoxazole 1, 4
  • Doxycycline 1
  • Clindamycin 1, 4

• IV options:

  • Vancomycin 1
  • Linezolid 1
  • Daptomycin 1
  • Telavancin 1

Treatment Algorithm

1. Assess severity and need for hospitalization:

   • Hospitalize if: signs of systemic toxicity, altered mental status, hemodynamic instability, deeper infection concerns, poor adherence, or severely immunocompromised 1
   • Otherwise, treat as outpatient

2. Determine if purulent or non-purulent:

   • For purulent cellulitis: incision and drainage is primary treatment 1
   • For non-purulent cellulitis: proceed with antibiotic selection

3. Select appropriate antibiotic:

   • Standard case (no MRSA risk factors): Cephalexin, penicillin, or clindamycin (if penicillin-allergic)
   • With MRSA risk factors: Add or switch to MRSA-active agent

4. Determine route:

   • Oral therapy for mild-moderate cases
   • IV therapy for severe cases or treatment failures
   • Consider research showing oral therapy may be as effective as parenteral therapy for uncomplicated cases 5

5. Set duration:

   • 5-6 days for uncomplicated cases with good response
   • Consider extending to 10-14 days for immunocompromised patients, diabetics, severe infections, or slow clinical response 1

Monitoring and Follow-up

• Monitor daily for clinical response 1
• Consider extending treatment if infection has not improved after 5 days 2
• Transition from IV to oral therapy when improvement is observed 1
• Watch for complications such as abscess formation or progression to necrotizing fasciitis 1

Prevention of Recurrence

• For patients with 3-4 episodes per year, consider prophylactic antibiotics:
  • Oral penicillin or erythromycin twice daily for 4-52 weeks
  • Intramuscular benzathine penicillin every 2-4 weeks 1
• Identify and treat predisposing conditions (tinea pedis, venous eczema, trauma, edema, obesity) 1

Common Pitfalls to Avoid

1. Inadequate dosing: Weight-based dosing is important for optimal outcomes; inadequate dosing has been independently associated with clinical failure 1
2. Unnecessarily prolonged therapy: 5-6 days is sufficient for most uncomplicated cases 2, 1, 3
3. Overuse of MRSA coverage: Standard streptococcal coverage is appropriate for most non-purulent cellulitis 2, 1
4. Failure to drain purulent collections: Incision and drainage is the primary treatment for any abscess or purulent collection 1
5. Missing underlying predisposing conditions: Address factors like tinea pedis or venous insufficiency to prevent recurrence 1