What is the recommended dose of antibiotics for treating cellulitis?

Antibiotic Dosing for Cellulitis Treatment

For typical non-purulent cellulitis, a 5-day course of antibiotics active against streptococci is recommended as first-line therapy, with extension only if the infection has not improved within this period. 1

First-Line Oral Antibiotic Options for Adults

• Cephalexin: 500 mg orally four times daily 1
• Dicloxacillin: 500 mg orally four times daily 1
• Clindamycin: 300-450 mg orally four times daily (for penicillin-allergic patients) 1
• Penicillin VK: 250-500 mg orally every 6 hours 1
• Doxycycline/Minocycline: 100 mg orally twice daily (not recommended for children <8 years) 1

Pediatric Dosing

• Cephalexin: 25-50 mg/kg/day divided in 4 doses 1
• Clindamycin: 30-40 mg/kg/day in 3 divided doses orally 1
• Penicillin: Appropriate weight-based dosing (refer to pediatric guidelines) 1

Duration of Therapy

• 5-6 days is sufficient for uncomplicated cellulitis 1, 2
• Extend treatment only if the infection has not improved within the initial 5-day period 1
• Research shows that 5 days of therapy with appropriate antibiotics is as effective as 10 days for uncomplicated cellulitis (98% success rate in both groups) 2, 3

When to Consider MRSA Coverage

• Standard non-purulent cellulitis typically does not require MRSA coverage 4, 5
• Add MRSA coverage in patients with:
  • Penetrating trauma 1
  • Evidence of MRSA infection elsewhere 1
  • Nasal colonization with MRSA 1
  • Injection drug use 1
  • Systemic inflammatory response syndrome (SIRS) 1
  • Failure to respond to beta-lactam therapy 1

MRSA Coverage Options

• Trimethoprim-sulfamethoxazole: 1-2 double-strength tablets orally twice daily 1
• Clindamycin: 600 mg orally three times daily 1
• Linezolid: 600 mg orally twice daily 1
• Doxycycline: 100 mg orally twice daily 1

Inpatient Treatment for Severe Cellulitis

• Vancomycin: 30 mg/kg/day in 2 divided doses IV 1
• Clindamycin: 600-900 mg IV every 6-8 hours 1
• Cefazolin: 1 g IV every 8 hours 1
• For severe infections: Vancomycin plus either piperacillin-tazobactam or imipenem/meropenem 1

Special Considerations

• High-dose cephalexin (1000 mg four times daily) may reduce treatment failure compared to standard dosing (500 mg four times daily), though with slightly more minor adverse effects 6
• Consider adjunctive anti-inflammatory therapy (e.g., ibuprofen) to hasten resolution of inflammation 7
• Systemic corticosteroids (prednisone 40 mg daily for 7 days) could be considered in non-diabetic adult patients 1, 5
• Elevate the affected area to reduce edema 1, 4
• Examine interdigital toe spaces in lower extremity cellulitis to identify and treat predisposing factors 1

Hospitalization Criteria

• Systemic inflammatory response syndrome (SIRS) 1
• Altered mental status 1
• Hemodynamic instability 1
• Concern for deeper or necrotizing infection 1
• Poor adherence to therapy 1
• Severe immunocompromise 1
• Failure of outpatient treatment 1

Prevention of Recurrence

• Identify and treat predisposing conditions (edema, obesity, eczema, venous insufficiency, toe web abnormalities) 1
• For patients with 3-4 episodes per year, consider prophylactic antibiotics such as oral penicillin or erythromycin twice daily for 4-52 weeks 1

Common Pitfalls to Avoid

• Don't extend treatment unnecessarily beyond 5 days if clinical improvement has occurred 1, 2
• Don't automatically add MRSA coverage for typical non-purulent cellulitis without specific risk factors 4, 5
• Don't miss examining interdigital spaces in lower extremity cellulitis 1
• Don't forget to elevate the affected area as an important adjunctive measure 1, 4