What is the appropriate dosage and treatment duration of cephalexin (Cephalexin) for uncomplicated cellulitis?

Cephalexin for Uncomplicated Cellulitis

For uncomplicated cellulitis, cephalexin should be administered at 500 mg orally four times daily for 5-6 days, which is as effective as longer courses while reducing antibiotic exposure. 1

Dosing Recommendations

• Adult dosage: 500 mg orally four times daily (2 grams total daily dose) 2
• Pediatric dosage: 25-50 mg/kg/day divided into four doses 2
• For severe infections, dosage may be doubled to 1000 mg four times daily, not exceeding 4 grams daily 2

Duration of Therapy

• 5-6 days is sufficient for uncomplicated cellulitis with good clinical response 1
• The 2019 National Institute for Health and Care Excellence (NICE) guideline recommends 5-7 days 1
• A randomized controlled trial demonstrated that 5 days of therapy was equivalent to 10 days for uncomplicated cellulitis (98% success rate in both groups) 3
• Consider extending treatment only if infection has not improved after 5 days 1

Rationale for Cephalexin as First-Line

• Cephalexin is recommended as first-line therapy due to excellent coverage against β-hemolytic streptococci, which are the predominant pathogens in uncomplicated cellulitis 4
• First-generation cephalosporins like cephalexin effectively target the most common causative organisms while limiting unnecessary broad-spectrum coverage 1
• Penicillinase-resistant penicillins (like flucloxacillin) are equally effective alternatives 4

MRSA Considerations

• Standard cephalexin therapy is appropriate for typical uncomplicated cellulitis without evidence of MRSA 1
• MRSA coverage should only be considered in specific circumstances:
  • Cellulitis associated with penetrating trauma 1
  • Evidence of MRSA infection elsewhere 1
  • Nasal colonization with MRSA 1
  • History of injection drug use 1
  • Presence of systemic inflammatory response syndrome 1
  • Purulent drainage 1
• Adding trimethoprim-sulfamethoxazole to cephalexin for empiric MRSA coverage did not improve outcomes in uncomplicated cellulitis 5, 6

Monitoring and Follow-up

• Clinical improvement should be evident within 48-72 hours of starting therapy 4
• Signs of improvement include:
  • Reduction in erythema, swelling, and tenderness 4
  • Resolution of systemic symptoms (if present) 4
• Consider alternative therapy or hospitalization if:
  • No improvement after 48-72 hours 1
  • Worsening symptoms despite appropriate therapy 1
  • Development of systemic symptoms 1

Adjunctive Measures

• Elevation of the affected area to promote drainage of edema and inflammatory substances 1
• Treatment of predisposing factors (tinea pedis, venous eczema, trauma) 1
• For recurrent cellulitis, address underlying conditions such as lymphedema, venous insufficiency, or obesity 1

Common Pitfalls to Avoid

• Unnecessarily prolonging antibiotic therapy beyond 5-6 days when clinical improvement occurs 1
• Adding MRSA coverage when not indicated for typical uncomplicated cellulitis 5, 6
• Failing to elevate the affected limb, which is an important but often neglected aspect of treatment 1
• Not addressing predisposing factors that may lead to recurrence 1