What is the recommended antibiotic dose for cellulitis?

Recommended Antibiotic Dosing for Cellulitis

For typical uncomplicated cellulitis, a 5-day course of an antibiotic active against streptococci is recommended as first-line therapy, with extension only if clinical improvement has not occurred by day 5. 1

Initial Antibiotic Selection Algorithm

For Mild Uncomplicated Cellulitis (outpatient, no systemic signs):

• First-line oral options:
  • Cephalexin 500 mg four times daily 1
  • Dicloxacillin 500 mg four times daily 1
  • Penicillin VK 250-500 mg every 6 hours 1
  • Amoxicillin 500 mg three times daily 1
  • Clindamycin 300-450 mg four times daily (for penicillin allergy) 1

For Moderate Cellulitis (systemic signs without MRSA risk factors):

• Add coverage for MSSA:
  • Cephalexin 500 mg four times daily 1
  • Dicloxacillin 500 mg four times daily 1

For Severe Cellulitis (hospitalization required):

• IV options:
  • Cefazolin 1 g every 8 hours 1
  • Clindamycin 600-900 mg every 6-8 hours (for penicillin allergy) 1
  • Penicillin 2-4 million units every 4-6 hours (for confirmed streptococcal infection) 1

For Cellulitis with MRSA Risk Factors:

(Penetrating trauma, MRSA elsewhere, MRSA colonization, injection drug use, or SIRS)

• Oral options:

  • Clindamycin 300-450 mg four times daily 1
  • Trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily 1
  • Doxycycline 100 mg twice daily 1
  • Linezolid 600 mg twice daily (reserve for severe cases) 1

• IV options:

  • Vancomycin 15 mg/kg every 12 hours 1
  • Daptomycin 4 mg/kg once daily 1
  • Linezolid 600 mg every 12 hours 1
  • Ceftaroline 600 mg twice daily 1

Duration of Therapy

• Standard duration: 5 days 1
• Extend therapy only if no improvement after 5 days 1
• Research shows 5-day courses are as effective as 10-day courses for uncomplicated cellulitis 2

Special Considerations

Pediatric Dosing

• Cephalexin: 25-50 mg/kg/day in 4 divided doses 1
• Clindamycin: 30-40 mg/kg/day in 3 divided doses 1
• Penicillin: 100,000 units/kg/day 1

Adjunctive Measures

• Elevate affected area to promote drainage of edema 1
• Treat predisposing conditions (tinea pedis, venous eczema, etc.) 1
• Examine interdigital toe spaces in lower-extremity cellulitis 1
• Consider systemic corticosteroids (prednisone 40 mg daily for 7 days) in non-diabetic adults 1

Important Clinical Pearls

1. MRSA coverage is usually unnecessary for typical cellulitis - Studies show β-lactam therapy alone is successful in 96% of typical cellulitis cases 1

2. Avoid combination therapy for typical cellulitis - Research demonstrates that adding trimethoprim-sulfamethoxazole to cephalexin does not improve outcomes for uncomplicated cellulitis 3, 4

3. Cultures are not routinely needed except in patients with:

   • Malignancy on chemotherapy
   • Neutropenia
   • Severe immunodeficiency
   • Immersion injuries
   • Animal bites
   • Systemic toxicity 1

4. Consider hospitalization for patients with:

   • SIRS (Systemic Inflammatory Response Syndrome)
   • Altered mental status
   • Hemodynamic instability
   • Concern for deeper/necrotizing infection
   • Poor adherence to therapy
   • Severe immunocompromise
   • Failure of outpatient therapy 1

5. For recurrent cellulitis (3-4 episodes per year), consider prophylactic antibiotics such as penicillin or erythromycin twice daily for extended periods 1