What is the recommended length of treatment with Keflex (cephalexin) for cellulitis?

Recommended Length of Treatment with Keflex (Cephalexin) for Cellulitis

The recommended duration of treatment with Keflex (cephalexin) for cellulitis is 5 days, but treatment should be extended if the infection has not improved within this time period. 1, 2

Evidence-Based Recommendations

The 2014 Infectious Diseases Society of America (IDSA) guidelines provide strong, high-quality evidence supporting a 5-day course of antibiotics for typical cases of cellulitis, with extension of therapy if clinical improvement is not observed within this timeframe 1.

More recent evidence from 2021 continues to support shorter courses:

• The American College of Physicians best practice advice recommends 5-6 days of therapy for uncomplicated cellulitis 1
• The UK's National Institute for Health and Care Excellence (NICE) guideline recommends a course of 5-7 days 1

Treatment Algorithm

Initial Assessment and Treatment

1. For typical, uncomplicated cellulitis without systemic signs of infection:

   • Cephalexin 500mg orally four times daily for 5 days 1, 2
   • Alternative: High-dose cephalexin 1000mg four times daily may be considered for more severe cases 3

2. For cellulitis with systemic signs of infection:

   • Consider broader coverage including MSSA
   • If risk factors for MRSA are present (penetrating trauma, evidence of MRSA elsewhere, nasal colonization with MRSA, injection drug use), add coverage for MRSA 1

Follow-up and Treatment Duration

• Reassess after 5 days of treatment
• If improvement is seen: Complete the 5-day course
• If inadequate improvement: Extend treatment until 2-3 days after clinical resolution 1, 2

Special Considerations

Patient Factors That May Affect Treatment

• Obesity: Standard cephalexin dosing appears effective in morbidly obese patients (BMI ≥40 kg/m²) with similar failure rates compared to non-obese patients 4
• Recurrent cellulitis: For patients with 3-4 episodes per year, prophylactic antibiotics may be considered 1, 2

Adjunctive Measures

• Elevate the affected area 1
• Treat predisposing factors such as edema, underlying skin disorders, or interdigital toe space abnormalities 1, 2
• Consider systemic corticosteroids in non-diabetic adult patients with cellulitis (weak recommendation) 1

Common Pitfalls to Avoid

1. Unnecessarily prolonged therapy:

   • Longer courses (>5 days) have not demonstrated superior outcomes for uncomplicated cases 1, 2
   • Extended courses increase risk of adverse effects and antimicrobial resistance

2. Inadequate follow-up:

   • Daily monitoring until definite improvement is essential 2
   • Failure to extend therapy when clinical improvement is not observed by day 5

3. Inappropriate antibiotic selection:

   • Using TMP-SMX alone for non-purulent cellulitis (poor activity against streptococci) 2
   • Adding TMP-SMX to cephalexin does not improve outcomes in uncomplicated cellulitis 5

In conclusion, while traditional practice has often defaulted to 7-10 day courses of antibiotics for cellulitis, current high-quality evidence supports a 5-day course of cephalexin for uncomplicated cellulitis, with extension of therapy only if clinical improvement is not observed within this timeframe.