What is the recommended treatment for cellulitis (inflammation of the skin and subcutaneous tissues) in the lower extremities?

Treatment of Lower Extremity Cellulitis

For non-purulent cellulitis of the lower extremities, the first-line treatment is beta-lactam antibiotics such as cephalexin 500 mg orally 4 times daily for 5-7 days. 1

Antibiotic Selection Based on Presentation

Non-purulent Cellulitis

• First-line therapy:
  • Cephalexin 500 mg orally 3-4 times daily for 5-6 days 1
  • Targets primarily streptococci, which along with Staphylococcus aureus are the most common causative organisms in cellulitis 2

Purulent Cellulitis or Abscess

• Primary treatment: Incision and drainage is essential 1
• Adjunctive antibiotics:
  • Clindamycin 300-450 mg orally three times daily for 5-6 days 1
  • Doxycycline 100 mg twice daily for 5-6 days (avoid in children under 8 years and pregnant women) 1
  • Trimethoprim-sulfamethoxazole (consider for MRSA coverage) 1

Severe Infections Requiring Hospitalization

• Vancomycin plus either piperacillin-tazobactam, ampicillin-sulbactam, or a carbapenem 1
• De-escalate based on culture results when available 1

MRSA Considerations

Consider MRSA coverage in patients with:

• Previous MRSA infection or colonization
• Injection drug use
• Systemic inflammatory response syndrome (SIRS)
• Failed initial antibiotic treatment
• Immunocompromised status 1

Duration of Treatment

• Standard duration: 5-7 days for uncomplicated infections 1
• Extend treatment if symptoms have not improved after initial course
• Continuing antibiotics beyond 7 days for uncomplicated infections is generally unnecessary 1

Monitoring Response

• Patients should show improvement within 72 hours of starting treatment
• If no improvement after 72 hours:
  1. Reevaluate diagnosis
  2. Consider drainage procedure if not already performed
  3. Change antibiotic therapy 1

Common Pitfalls to Avoid

1. Failing to perform incision and drainage for abscesses 1
2. Not considering MRSA coverage in high-prevalence areas 1
3. Using inappropriate antibiotic dosing 1
4. Not addressing predisposing factors that can lead to recurrence 2
5. Misdiagnosis - conditions commonly mistaken for cellulitis include venous stasis dermatitis, contact dermatitis, deep vein thrombosis, and panniculitis 3

Prevention of Recurrence

Address predisposing factors, particularly:

• Toe web intertrigo (significantly associated with recurrent cellulitis) 4
• Peripheral vascular disease 4
• Varicose veins 4

Evidence Strength

The recommendations are primarily based on guidelines from the Infectious Diseases Society of America 1. Clinical studies support the effectiveness of narrow-spectrum antibiotics (targeting streptococci and methicillin-sensitive S. aureus) for uncomplicated cellulitis, with no significant difference in outcomes compared to broad-spectrum antibiotics 5.