What is the recommended dose of Keflex (Cephalexin) for a patient with cellulitis on the foot?

Keflex (Cephalexin) Dosing for Cellulitis of the Foot

For patients with cellulitis on the foot, the recommended dose of cephalexin is 500 mg orally four times daily for 5 days, extending treatment if the infection has not improved within this time period. 1, 2

First-Line Treatment Recommendations

• Cephalexin 500 mg orally every 6 hours (four times daily) is the standard recommended dose for adults with cellulitis 1, 2
• Treatment duration should be 5 days initially, with extension if clinical improvement has not occurred by day 5 1
• Cephalexin is particularly effective against streptococci, which are the predominant pathogens in non-purulent cellulitis 1, 3
• For severe infections, higher doses up to 1 gram four times daily (within the FDA-approved range of 1-4 grams daily) may be considered 2, 4

Treatment Algorithm

Step 1: Assess Severity and Complications

• For mild to moderate cellulitis without systemic symptoms (no SIRS, altered mental status, or hemodynamic instability), outpatient therapy with oral antibiotics is appropriate 1
• For severe cellulitis with systemic symptoms, hospitalization and parenteral therapy may be required 1

Step 2: Antibiotic Selection

• For typical, non-purulent cellulitis of the foot:
  • First choice: Cephalexin 500 mg orally four times daily 1, 2
  • Alternative options if penicillin allergic: Clindamycin 300-450 mg orally four times daily 1

Step 3: Consider MRSA Coverage Only If:

• Cellulitis is associated with penetrating trauma 1
• Evidence of MRSA infection elsewhere 1
• Purulent drainage is present 3
• Patient has history of injection drug use 1
• If MRSA coverage is needed, options include:
  • Clindamycin alone 3
  • Combination of SMX-TMP or doxycycline with a β-lactam 3

Important Adjunctive Measures

• Elevation of the affected foot is crucial to promote gravity drainage of edema and inflammatory substances 1
• Examine interdigital toe spaces carefully, as treating fissuring, scaling, or maceration may eradicate colonization with pathogens and reduce recurrence 1, 3
• Consider systemic corticosteroids (e.g., prednisone 40 mg daily for 7 days) in non-diabetic patients to hasten resolution 1, 5
• Identify and treat predisposing conditions such as edema, obesity, venous insufficiency, and toe web abnormalities 1, 3

Special Considerations

• A recent study showed that high-dose cephalexin (1000 mg four times daily) may have fewer treatment failures compared to standard dose (500 mg four times daily), but with more minor adverse effects 4
• For patients with frequent recurrent episodes (3-4 per year), prophylactic antibiotics may be considered 1, 3
• Adding MRSA coverage with trimethoprim-sulfamethoxazole to cephalexin did not significantly improve outcomes in uncomplicated cellulitis in the per-protocol analysis of a randomized trial 6

Common Pitfalls to Avoid

• Don't automatically extend treatment beyond 5 days if clinical improvement has occurred 3
• Don't routinely add MRSA coverage for typical non-purulent cellulitis without specific risk factors 3, 6
• Don't forget to examine and treat interdigital toe spaces in lower-extremity cellulitis 1, 3
• Don't overlook the importance of elevating the affected foot, especially in patients with venous insufficiency or lymphedema 1, 3