What are the recommended antibiotics for treating cellulitis?

Recommended Antibiotics for Cellulitis

For non-purulent cellulitis, first-line therapy includes cephalexin 500 mg orally four times daily, dicloxacillin 500 mg orally four times daily, or amoxicillin-clavulanate 875/125 mg orally twice daily for 5-7 days. 1

Antibiotic Selection Algorithm

Non-purulent Cellulitis (Most Common)

• First-line options:

  • Cephalexin 500 mg orally four times daily
  • Dicloxacillin 500 mg orally four times daily
  • Amoxicillin-clavulanate 875/125 mg orally twice daily 1

• For penicillin allergy:

  • Clindamycin 300-450 mg orally three times daily 1

When MRSA Coverage is Needed

MRSA coverage should be considered if any of these risk factors are present:

• History of MRSA infection
• Active injection drug use
• Purulent drainage
• Systemic inflammatory response syndrome 1

MRSA coverage options:

• Trimethoprim-sulfamethoxazole
• Doxycycline
• Clindamycin
• Linezolid
• Vancomycin (for severe cases requiring IV therapy) 1

Severe Cellulitis or Unable to Tolerate Oral Medications

Parenteral therapy options:

• Nafcillin
• Cefazolin
• Clindamycin
• Vancomycin (for penicillin allergy or MRSA concern) 1

Duration of Therapy

5-7 days is sufficient for uncomplicated cellulitis if clinical improvement occurs within this timeframe 1. This is supported by research showing that 5 days of therapy with levofloxacin is as effective as 10 days for uncomplicated cellulitis, with a 98% success rate in both groups 2.

Special Considerations

Pediatric Patients

• Amoxicillin-clavulanate: 40 mg/kg/day divided into two doses (not exceeding 875/125 mg twice daily) for 5 days if clinical improvement occurs 1

Important Management Principles

• Elevation of the affected area to promote drainage of edema 1
• Examine and treat predisposing conditions (tinea pedis, venous eczema, etc.) 1
• Monitor daily until improvement is observed 1

Evidence on Combination Therapy

Adding trimethoprim-sulfamethoxazole to cephalexin does not improve outcomes for typical non-purulent cellulitis. In a randomized controlled trial, the cure rate was 85% with combination therapy versus 82% with cephalexin alone (p=0.66) 3.

Route of Administration

For patients with similar severity of cellulitis, oral antibiotics appear to be as effective as intravenous therapy. A study found that patients given only oral therapy were more likely to have improved at day 5 compared to those given IV therapy, and were equally likely to return to normal activities by day 10 4.

Common Pitfalls to Avoid

1. Overuse of broad-spectrum antibiotics for typical non-purulent cellulitis 1
2. Unnecessary MRSA coverage for typical cellulitis without risk factors 1
3. Inadequate duration of therapy - 5 days is sufficient for uncomplicated cases, but more severe cases may require 7-10 days 1
4. Failure to elevate the affected area, which is crucial for reducing edema 1
5. Overlooking underlying conditions that may predispose to recurrence 1
6. Inadequate follow-up for outpatient cases 1

Remember to consider hospitalization if signs of systemic infection develop, mental status changes occur, hemodynamic instability develops, deeper or necrotizing infection is suspected, poor adherence to therapy is likely, or outpatient treatment is failing 1.