Treatment of Impetigo
For limited impetigo, use topical mupirocin 2% ointment applied three times daily for 5-7 days as first-line therapy; for extensive disease, multiple sites, or treatment failure, switch to oral antibiotics such as cephalexin or dicloxacillin. 1
First-Line Treatment: Topical Antibiotics for Limited Disease
Topical therapy is the preferred initial approach for localized impetigo:
- Mupirocin 2% ointment applied three times daily for 5-7 days is the gold standard first-line treatment recommended by both the American Academy of Pediatrics and the Infectious Diseases Society of America 1, 2
- Retapamulin 1% ointment applied twice daily for 5 days is an effective alternative 1
- Topical antibiotics demonstrate superior cure rates compared to placebo (RR 2.24,95% CI 1.61-3.13) and are associated with fewer side effects than oral therapy 3
- Mupirocin and fusidic acid show equivalent efficacy when compared head-to-head (RR 1.03,95% CI 0.95-1.11) 3
Second-Line Treatment: Oral Antibiotics for Extensive Disease
Oral antibiotics are indicated when:
- Impetigo is extensive or involves multiple body sites 1, 4
- Topical therapy is impractical (e.g., scalp involvement, numerous lesions) 1, 4
- First-line topical treatment has failed 1
- Systemic symptoms are present 1
Recommended oral antibiotic regimens:
For Methicillin-Susceptible S. aureus (MSSA):
- Dicloxacillin 250 mg four times daily for adults 4
- Cephalexin 250-500 mg four times daily for adults (adjust by weight for children) 4
- These agents provide coverage against both S. aureus and S. pyogenes 1
Critical Pitfall to Avoid:
- Penicillin alone is NOT effective for impetigo as it lacks adequate coverage against S. aureus 4, 5
- Penicillin V is inferior to erythromycin (RR 1.29,95% CI 1.07-1.56) and cloxacillin (RR 1.59,95% CI 1.21-2.08) 3
Special Considerations for MRSA
Consider empiric MRSA coverage when:
- Patient is at risk for community-acquired MRSA (CA-MRSA) 1
- Failure to respond to first-line therapy after 48-72 hours 4
- High local prevalence of CA-MRSA 1
MRSA-directed therapy options:
- Clindamycin 300-450 mg three times daily for adults 4
- Trimethoprim-sulfamethoxazole (TMP-SMX) 1, 4
- Doxycycline (contraindicated in children under 8 years) 1, 4
Important caveat: TMP-SMX covers MRSA but is inadequate for streptococcal infection, so consider combination therapy or alternative agents if streptococcal infection cannot be excluded 5
Treatment Duration and Monitoring
- Topical treatment: 5-7 days 1, 4
- Oral antibiotics: 5-10 days 4
- Re-evaluate if no improvement after 48-72 hours of appropriate therapy 4
- Complete the full antibiotic course even if symptoms improve quickly to prevent complications such as post-streptococcal glomerulonephritis 1
Comparative Efficacy: Topical vs. Oral Therapy
Topical mupirocin demonstrates slight superiority over oral erythromycin (pooled RR 1.07,95% CI 1.01-1.13) in studies with 581 participants 3. This finding, combined with the lower side-effect profile of topical therapy (primarily gastrointestinal effects with oral agents), supports topical therapy as first-line for limited disease 3.
Culture Guidance
Obtain cultures when:
- Treatment failure occurs 4
- MRSA is suspected 4
- Recurrent infections are present 4
- Adjust antimicrobial therapy based on susceptibility results 4