What is the recommended dose of Keflex (Cephalexin) for treating cellulitis?

Keflex (Cephalexin) Dosing for Cellulitis

For typical non-purulent cellulitis in adults, the recommended dose of Keflex (cephalexin) is 500 mg orally every 6 hours for 5-7 days. 1, 2

Dosing Guidelines

Adults:

• Standard dose: 500 mg orally every 6 hours 1, 2
• Alternative dosing: 1 gram orally every 12 hours for skin and skin structure infections 2
• Duration: 5 days is recommended for uncomplicated cellulitis, but treatment should be extended if the infection has not improved within this time period 1
• Maximum daily dose: 4 grams per day 2

Pediatric Patients:

• Standard dose: 25-50 mg/kg/day divided into 4 doses 2
• Alternative dosing: Total daily dose may be divided and administered every 12 hours 2
• Duration: Same as adults (5 days with extension if needed) 1

Clinical Decision Algorithm

1. Assess severity of cellulitis:

   • Mild (no systemic signs): Oral cephalexin is appropriate 1
   • Moderate (with systemic signs): Consider coverage for both streptococci and MSSA 1
   • Severe (with SIRS, altered mental status, or hemodynamic instability): Hospitalize for IV antibiotics 1

2. Consider MRSA coverage only if:

   • Penetrating trauma history 1
   • Evidence of MRSA infection elsewhere 1
   • Nasal colonization with MRSA 1
   • Injection drug use 1
   • Presence of purulent drainage 1
   • Failure of initial β-lactam therapy 1

3. Special considerations:

   • For facial cellulitis, cephalexin 250 mg four times daily has shown efficacy 3
   • Recent evidence suggests high-dose cephalexin (1000 mg four times daily) may reduce treatment failure rates compared to standard dosing (12.9% vs 3.2% failure), but with more minor adverse effects 4

Important Clinical Pearls

• Elevate the affected area to promote drainage of edema and inflammatory substances 1
• Examine interdigital toe spaces in lower-extremity cellulitis to identify and treat predisposing factors 1
• Blood cultures are generally unnecessary for typical cases but should be considered in patients with malignancy, neutropenia, severe immunodeficiency, or systemic toxicity 1
• The addition of trimethoprim-sulfamethoxazole to cephalexin does not improve outcomes for non-purulent cellulitis 5
• Consider systemic corticosteroids (prednisone 40 mg daily for 7 days) in non-diabetic adults with cellulitis to hasten resolution 1

Common Pitfalls to Avoid

• Overtreatment: MRSA is an unusual cause of typical cellulitis. Treatment for MRSA is usually unnecessary unless specific risk factors are present 1
• Inadequate duration: While 5 days is recommended, treatment should be extended if clinical improvement has not occurred 1
• Missing predisposing factors: Identify and treat conditions such as edema, obesity, eczema, venous insufficiency, and toe web abnormalities 1
• Failure to elevate: Elevation of the affected area hastens improvement 1
• Unnecessary hospitalization: Outpatient therapy is appropriate for patients without SIRS, altered mental status, or hemodynamic instability 1

Twice-daily dosing with cephalexin (500 mg every 12 hours) may be considered to enhance compliance, as it has shown efficacy in treating staphylococcal skin infections 6, though the FDA-approved dosing for cellulitis is 500 mg every 6 hours 2.