What is the treatment for cellulitis of the lower limb?

Treatment of Cellulitis in the Lower Limb

The first-line treatment for uncomplicated cellulitis of the lower limb is oral cephalexin 500 mg 3-4 times daily for 5-6 days, targeting Streptococcus and methicillin-sensitive Staphylococcus aureus. 1

Antibiotic Selection Algorithm

First-Line Options

• Cephalexin: 500 mg orally 3-4 times daily for 5-6 days
  • Gold standard for uncomplicated cellulitis with cure rates of 90% or higher 1
  • Targets the most common pathogens (Streptococcus and Staphylococcus aureus)

Alternative Options (for penicillin allergies)

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

  • Particularly useful for penicillin-allergic patients
  • Provides coverage against MRSA, streptococci, and anaerobes
  • Caution: Higher risk of Clostridioides difficile infection

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

  • Contraindicated in pregnant women in third trimester and children under 8 years

For MRSA Risk Factors

If patient has prior MRSA infection, frequent hospitalizations, or is immunocompromised:

• Add trimethoprim-sulfamethoxazole (1-2 DS tablets orally twice daily) or switch to clindamycin 1

For Severe Infections Requiring IV Therapy

• Ceftriaxone: 50 mg/kg per day (parenteral) 1
• Linezolid: 600 mg IV/PO every 12 hours 2
  • Shown to be effective in complicated skin infections with 90% cure rate in clinically evaluable patients 2
  • Particularly useful for MRSA infections (79% cure rate) 2

Special Considerations

Diabetic Foot Infections

• Require more aggressive treatment approach
• Linezolid 600 mg every 12 hours has shown 83% cure rate in clinically evaluable patients 2
• Consider surgical debridement and off-loading as adjunctive treatments 1, 2

Abscesses

• Incision and drainage is the primary treatment for abscesses 1
• Antibiotics alone are insufficient for abscess treatment
• Simple abscesses may not require antibiotics after adequate drainage 1

Monitoring Response

• Most patients should show improvement within 48-72 hours of starting appropriate therapy 1
• If no improvement after 72 hours:
  1. Reevaluate diagnosis
  2. Consider changing antibiotic therapy
  3. Evaluate for abscess formation requiring drainage 1

Duration of Treatment

• 5-day course is as effective as a 10-day course for uncomplicated cellulitis if clinical improvement occurs by day 5 1
• Standard treatment duration is 5-7 days for most skin infections 1

Common Pitfalls to Avoid

1. Misdiagnosis: Venous insufficiency, eczema, deep vein thrombosis, and gout are frequently mistaken for cellulitis 3
2. Inadequate coverage for resistant organisms: Particularly in frequently hospitalized patients 1
3. Unnecessary MRSA coverage in areas with low MRSA prevalence 1
4. Treating for too long: 5-6 days is typically sufficient for uncomplicated cases 1
5. Failure to elevate the affected limb as an important adjunctive measure 1
6. Not considering underlying predisposing factors that may lead to recurrence 1, 4

Evidence on Combination Therapy

Research has not shown benefit of combination therapy over monotherapy:

• Adding benzylpenicillin to flucloxacillin showed no significant difference in treatment response 5
• Adding clindamycin to flucloxacillin doubled the likelihood of diarrhea without improving outcomes 6

The treatment of cellulitis should focus on appropriate antibiotic selection based on likely pathogens, with special consideration for patient-specific risk factors and local resistance patterns.