Is cephalexin (cephalexin) effective for treating impetigo?

Cephalexin for Impetigo Treatment

Cephalexin is highly effective for treating impetigo and is recommended as a first-line oral antibiotic option with dosing of 250 mg four times daily for adults or 25-50 mg/kg/day in 3-4 divided doses for children. 1, 2

Efficacy and Indications

Cephalexin is specifically indicated for skin and skin structure infections caused by Staphylococcus aureus and/or Streptococcus pyogenes 3, which are the primary pathogens responsible for impetigo:

• Nonbullous impetigo (70% of cases): Caused by S. aureus or S. pyogenes
• Bullous impetigo (30% of cases): Caused exclusively by S. aureus 2

Clinical studies have demonstrated that cephalexin achieves cure rates of 90% or higher for streptococcal and staphylococcal skin infections 4. In direct comparison studies, cephalexin has shown superior efficacy compared to penicillin for impetigo treatment, with no treatment failures observed in patients treated with cephalexin 5.

Treatment Algorithm

1. For limited lesions:

   • Consider topical therapy with mupirocin 2% ointment or retapamulin applied twice daily 2

2. For more extensive impetigo or when topical therapy is impractical:

   • Use oral cephalexin:
     • Adults: 250 mg four times daily 1
     • Children: 25-50 mg/kg/day in 3-4 divided doses 1
     • Duration: 7 days 2

3. For confirmed MRSA infections:

   • Switch to appropriate MRSA-active agents such as trimethoprim-sulfamethoxazole, clindamycin, or linezolid 2

4. For penicillin-allergic patients:

   • Non-immediate hypersensitivity: Cephalexin can still be used 1, 2
   • Immediate hypersensitivity reactions (urticaria, angioedema, bronchospasm, anaphylaxis): Avoid cephalexin and use clindamycin (300-400 mg four times daily for adults) 1, 6

Advantages of Cephalexin

• Excellent bioavailability due to resistance to degradation by gastric acid 4
• Effective against both primary pathogens causing impetigo (S. aureus and S. pyogenes) 3
• Some studies suggest twice-daily dosing may be effective, potentially enhancing medication compliance 7
• Well-tolerated with mild and infrequent side effects 4

Clinical Pearls and Pitfalls

• Important: Penicillin alone is inadequate for impetigo treatment due to high rates of penicillin-resistant S. aureus 5, 6
• Evaluate clinical response within 48-72 hours of starting treatment 2
• If no improvement is seen within 3-5 days, consider:
  • Obtaining bacterial culture and sensitivity testing
  • Alternative diagnosis
  • Possible MRSA infection requiring different antibiotics 2
• Expected resolution of impetigo is within 7-10 days of starting appropriate treatment 2
• Consider community prevalence of MRSA when selecting empiric therapy 2

Prevention of Spread

• Keep lesions covered when possible
• Use separate towels and linens
• Practice good hand hygiene
• Change clothing that contacts affected areas daily 2

Cephalexin remains a highly effective treatment for impetigo with decades of clinical experience supporting its use, particularly when oral therapy is indicated for more extensive disease.