What are the recommended antibiotics for treating cellulitis of the lower extremity?

Antibiotic Therapy for Lower Extremity Cellulitis

For typical cases of lower extremity cellulitis, first-line therapy should be an antimicrobial agent active against streptococci, such as penicillin, amoxicillin, dicloxacillin, cephalexin, or clindamycin, with a recommended treatment duration of 5 days, extending if no improvement is seen. 1, 2

First-Line Treatment Options

Mild to Moderate Cellulitis (Outpatient)

• For typical cases without systemic signs, use antibiotics active against streptococci 1, 2:
  • Dicloxacillin 500 mg orally four times daily 1
  • Cephalexin 500 mg orally four times daily 1, 2
  • Clindamycin 300-450 mg orally three times daily (for penicillin-allergic patients) 1
  • Amoxicillin-clavulanate 875/125 mg orally twice daily 2

Severe Cellulitis (Inpatient)

• For patients with systemic inflammatory response syndrome (SIRS), altered mental status, or hemodynamic instability 1:
  • First-generation cephalosporin (cefazolin) 1-2 g IV every 8 hours 1, 2
  • Nafcillin or oxacillin 1-2 g IV every 4-6 hours 1
  • Clindamycin 600-900 mg IV every 8 hours (for penicillin-allergic patients) 1

Special Considerations for MRSA Coverage

• Add MRSA coverage ONLY if the following risk factors are present 1, 2, 3:

  • Penetrating trauma 1
  • Evidence of MRSA infection elsewhere 1, 2
  • Nasal colonization with MRSA 1
  • Injection drug use 1, 3
  • Systemic inflammatory response syndrome 1
  • Purulent drainage 2, 3
  • Prior MRSA exposure 3
  • High-risk populations (athletes, prisoners, military recruits, residents of long-term care facilities) 3

• MRSA treatment options 1, 4:

  • Vancomycin 15-20 mg/kg IV every 12 hours (inpatient) 1
  • Linezolid 600 mg IV/PO every 12 hours 4
  • Daptomycin, telavancin, or ceftaroline (alternatives) 2

Duration of Therapy

• 5 days is the recommended duration for uncomplicated cellulitis 1
• Extend treatment if infection has not improved within 5 days 1
• Clinical trials have shown that 5-6 days of therapy is as effective as 10-14 days for uncomplicated cellulitis 1

Adjunctive Measures

• Elevate the affected area to promote gravity drainage of edema 1
• Examine interdigital toe spaces for fissuring, scaling, or maceration that may harbor pathogens 1
• Treat predisposing factors such as edema, obesity, eczema, venous insufficiency, and tinea pedis 1, 2
• Consider systemic corticosteroids (prednisone 40 mg daily for 7 days) in non-diabetic adult patients to hasten resolution 1

Hospitalization Criteria

• Concern for deeper or necrotizing infection 1
• Presence of SIRS, altered mental status, or hemodynamic instability 1, 2
• Poor adherence to therapy 1
• Severe immunocompromise 1
• Failing outpatient treatment 1, 2

Management of Recurrent Cellulitis

• For patients with 3-4 episodes per year despite treatment of predisposing factors, consider prophylactic antibiotics 1, 2:
  • Oral penicillin or erythromycin twice daily for 4-52 weeks 1
  • Intramuscular benzathine penicillin every 2-4 weeks 1, 2

Common Pitfalls and Caveats

• MRSA is an unusual cause of typical cellulitis; unnecessary MRSA coverage should be avoided unless specific risk factors are present 2, 5
• Blood cultures are generally not necessary for typical cases but should be obtained in patients with malignancy, severe systemic signs, or unusual predisposing factors 2
• Many conditions can mimic cellulitis, including venous stasis dermatitis, contact dermatitis, and lymphedema 5
• Cultures of blood or cutaneous aspirates are not routinely recommended for typical cases due to poor sensitivity 2, 5