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, 2
First-Line Oral Antibiotic Options for Adults
- Cephalexin: 500 mg orally four times daily 2
- Dicloxacillin: 500 mg orally four times daily 2
- Clindamycin: 300-450 mg orally four times daily (for penicillin-allergic patients) 2
- Penicillin VK: 250-500 mg orally every 6 hours 2
- Doxycycline/Minocycline: 100 mg orally twice daily (not recommended for children <8 years) 2
Pediatric Dosing
- Cephalexin: 25-50 mg/kg/day divided in 4 doses 2
- Clindamycin: 30-40 mg/kg/day in 3 divided doses orally 2
- Penicillin: Appropriate weight-based dosing (refer to pediatric guidelines) 2
Duration of Therapy
- 5-6 days is sufficient for uncomplicated cellulitis 1, 3
- Extend treatment only if the infection has not improved within the initial 5-day period 2
- 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) 3, 4
When to Consider MRSA Coverage
- Standard non-purulent cellulitis typically does not require MRSA coverage 5, 6
- Add MRSA coverage in patients with:
MRSA Coverage Options
- Trimethoprim-sulfamethoxazole: 1-2 double-strength tablets orally twice daily 2, 7
- Clindamycin: 600 mg orally three times daily 2
- Linezolid: 600 mg orally twice daily 2
- Doxycycline: 100 mg orally twice daily 2, 7
Inpatient Treatment for Severe Cellulitis
- Vancomycin: 30 mg/kg/day in 2 divided doses IV 2
- Clindamycin: 600-900 mg IV every 6-8 hours 2
- Cefazolin: 1 g IV every 8 hours 2
- For severe infections: Vancomycin plus either piperacillin-tazobactam or imipenem/meropenem 2
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 8
- Consider adjunctive anti-inflammatory therapy (e.g., ibuprofen) to hasten resolution of inflammation 9
- Systemic corticosteroids (prednisone 40 mg daily for 7 days) could be considered in non-diabetic adult patients 2, 6
- Elevate the affected area to reduce edema 2, 5
- Examine interdigital toe spaces in lower extremity cellulitis to identify and treat predisposing factors 2
Hospitalization Criteria
- Systemic inflammatory response syndrome (SIRS) 2
- Altered mental status 2
- Hemodynamic instability 2
- Concern for deeper or necrotizing infection 2
- Poor adherence to therapy 2
- Severe immunocompromise 2
- Failure of outpatient treatment 2
Prevention of Recurrence
- Identify and treat predisposing conditions (edema, obesity, eczema, venous insufficiency, toe web abnormalities) 2
- For patients with 3-4 episodes per year, consider prophylactic antibiotics such as oral penicillin or erythromycin twice daily for 4-52 weeks 2
Common Pitfalls to Avoid
- Don't extend treatment unnecessarily beyond 5 days if clinical improvement has occurred 1, 3
- Don't automatically add MRSA coverage for typical non-purulent cellulitis without specific risk factors 5, 6
- Don't miss examining interdigital spaces in lower extremity cellulitis 2
- Don't forget to elevate the affected area as an important adjunctive measure 2, 5