What is the first-line treatment for cellulitis?

First-Line Treatment for Cellulitis

For non-purulent cellulitis, the first-line treatment is oral beta-lactam antibiotics (such as cephalexin or dicloxacillin) targeting streptococci and methicillin-sensitive Staphylococcus aureus for 5-6 days. 1, 2

Treatment Algorithm Based on Presentation

Non-purulent Cellulitis (most common)

• First-line therapy: Beta-lactam antibiotics 1, 2
  • Cephalexin 500 mg orally four times daily
  • Dicloxacillin 500 mg orally four times daily
  • Amoxicillin-clavulanate 875/125 mg orally twice daily
• Duration: 5-6 days 2, 1
• For penicillin allergy: Clindamycin 300-450 mg orally three times daily 2, 1

Purulent Cellulitis (with drainage/exudate)

• First-line therapy: Empiric coverage for CA-MRSA pending culture results 2
  • Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 DS tablets twice daily
  • Doxycycline 100 mg orally twice daily
  • Clindamycin 300-450 mg orally three times daily
• Duration: 5-10 days 2, 1

Severe Cellulitis Requiring Hospitalization

• First-line therapy: Intravenous antibiotics 2
  • Vancomycin IV
  • Ceftriaxone IV
  • Clindamycin IV 600 mg three times daily
• Duration: 7-14 days 2

Assessment and Follow-up

• Reassess after 48-72 hours to evaluate response 1
• If no improvement after 5 days, consider:
  1. Extending antibiotic duration
  2. Switching antibiotics (consider MRSA coverage)
  3. Reevaluating diagnosis 2, 1

Special Considerations

When to Consider MRSA Coverage

• Purulent drainage or exudate
• Previous MRSA infection or colonization
• Penetrating trauma
• Injection drug use
• Systemic inflammatory response syndrome
• Failure to respond to beta-lactam therapy 2, 1

When to Hospitalize

• Systemic toxicity (fever >38.5°C, tachycardia)
• Rapid progression of infection
• Extensive involvement
• Immunocompromised status
• Failure to respond to oral therapy within 48 hours 1

Common Pitfalls to Avoid

1. Unnecessary broad-spectrum antibiotics for typical non-purulent cellulitis 1
2. Inadequate duration of therapy - too short can lead to treatment failure, too long increases resistance risk 2
3. Failure to elevate the affected area to reduce edema 1
4. Overlooking underlying conditions that can lead to recurrence (e.g., tinea pedis, edema) 1
5. Misdiagnosis of cellulitis mimics such as venous stasis dermatitis, contact dermatitis, or deep vein thrombosis 3

Prevention of Recurrence

• Address predisposing factors (edema, obesity, venous insufficiency)
• Examine interdigital toe spaces for fissuring or maceration
• Maintain good personal hygiene
• Keep wounds covered with clean, dry bandages 2, 1

For patients with recurrent cellulitis (3-4 episodes per year), consider prophylactic antibiotics after addressing predisposing factors 1.