What are the recommended antibiotics for treating cellulitis?

Recommended Antibiotics for Cellulitis

For uncomplicated cellulitis, cephalexin 500 mg orally four times daily for 5-6 days is the first-line treatment, with clindamycin 300-450 mg three times daily as an alternative for penicillin-allergic patients. 1

First-Line Treatment Options

Standard Therapy (Non-MRSA Coverage)

• Cephalexin: 500 mg orally 3-4 times daily for 5-6 days 1

  • First-line therapy recommended by the Infectious Diseases Society of America
  • Effective against beta-hemolytic streptococci and methicillin-sensitive Staphylococcus aureus
  • Appropriate for most uncomplicated cellulitis cases

• Dicloxacillin: A penicillinase-resistant penicillin that can be used as an alternative to cephalexin 2

  • Should be used with caution in patients with penicillin allergy
  • May have reduced absorption if taken with food

For Penicillin-Allergic Patients

• Clindamycin: 300-450 mg orally three times daily for 5-6 days 1

  • Recommended alternative for patients with beta-lactam allergies
  • Provides coverage against both streptococci and staphylococci

• Doxycycline: 100 mg twice daily for 5-6 days 1

  • Recommended by the American College of Physicians
  • Particularly useful when MRSA is suspected or in patients with beta-lactam allergies

When to Consider MRSA Coverage

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 1

MRSA Treatment Options

• Oral options:

  • Doxycycline: 100 mg twice daily
  • Trimethoprim-sulfamethoxazole (TMP-SMX): However, research shows adding TMP-SMX to cephalexin did not improve outcomes for uncomplicated cellulitis 3

• IV options (for severe infections):

  • Vancomycin: 15-20 mg/kg IV every 8-12 hours 1, 4
  • Other options include daptomycin, linezolid, and telavancin 1

Treatment Duration and Monitoring

• Standard duration: 5-6 days is as effective as 10 days if clinical improvement occurs by day 5 1
• Patient reassessment: Within 48-72 hours of initiating therapy 1
• Consider changing therapy: If no improvement or worsening occurs within 48-72 hours, consider switching to MRSA-active therapy 1

Special Populations

Pediatric Patients

• Recommended dosage: 75-100 mg/kg/day divided into 3-4 doses 1
• Doxycycline should be avoided in children under 8 years of age 1

Patients with Recurrent Cellulitis

• Identify and treat predisposing conditions (edema, obesity, eczema, venous insufficiency, toe web abnormalities) 1
• Consider prophylactic antibiotics such as oral penicillin or erythromycin 1

Common Pitfalls and Caveats

1. Unnecessary MRSA coverage: Most non-purulent cellulitis is caused by beta-hemolytic streptococci and does not require MRSA coverage 5

2. Premature discontinuation: Patients should complete the full course of antibiotics even if symptoms improve quickly to prevent treatment failure and increased risk of resistance 1

3. Diagnostic confusion: Many clinical conditions can mimic cellulitis. If not responding to appropriate therapy, consider alternative diagnoses 5

4. Cultures: Blood and tissue cultures are unnecessary for typical cases of cellulitis but should be obtained for patients with:

   • Malignancy
   • Severe systemic features
   • Unusual predisposing factors
   • Neutropenia
   • Severe cell-mediated immunodeficiency 1

5. Adjunctive therapy: Consider elevation of the affected area to promote gravity drainage of edema and inflammatory substances 1

By following these evidence-based recommendations for antibiotic selection in cellulitis, clinicians can provide effective treatment while minimizing unnecessary broad-spectrum antibiotic use.