What is the recommended treatment for impetigo?

Treatment for Impetigo

For localized impetigo (limited lesions), treat with topical mupirocin or retapamulin twice daily for 5 days; for extensive disease or multiple lesions, use oral antibiotics for 7 days targeting S. aureus. 1

Treatment Algorithm Based on Disease Extent

Localized Disease (Few Lesions)

Topical therapy is first-line:

• Mupirocin 2% ointment applied twice daily for 5 days (strong evidence) 1
• Retapamulin 1% ointment applied twice daily for 5 days (strong evidence) 1

These topical agents are equally effective as oral antibiotics for limited disease and have the advantage of fewer systemic side effects 2, 3. Meta-analysis demonstrates topical antibiotics are significantly more effective than placebo (RR 2.24,95% CI 1.61-3.13) 2.

Extensive Disease (Numerous Lesions) or Outbreak Settings

Oral antibiotics are recommended to decrease transmission and for more rapid clearance 1:

First-line oral agents (7-day course):

• Dicloxacillin 250 mg four times daily (adults) or 25-50 mg/kg/day divided in 4 doses (children) 1
• Cephalexin 250 mg four times daily (adults) or 25-50 mg/kg/day divided in 3-4 doses (children) 1

These agents target methicillin-susceptible S. aureus (MSSA), which causes most impetigo cases 1.

If MRSA is suspected or confirmed:

• Doxycycline 100 mg twice daily (avoid in children <8 years) 1
• Clindamycin 300-400 mg four times daily (adults) or 20 mg/kg/day divided in 3 doses (children) 1
• Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets twice daily (adults) or 8-12 mg/kg/day based on TMP component (children) 1

If Streptococcus Alone is Cultured

Oral penicillin becomes the drug of choice, with macrolides or clindamycin as alternatives for penicillin-allergic patients 1.

Important Clinical Considerations

Culture is helpful but not mandatory: While Gram stain and culture can identify whether S. aureus and/or β-hemolytic Streptococcus is the cause, treatment without cultures is reasonable in typical cases 1. However, cultures should be obtained if MRSA is suspected or in treatment failures.

Topical vs. oral efficacy: Topical mupirocin has been shown slightly superior to oral erythromycin (pooled RR 1.07,95% CI 1.01-1.13) 2. There is no significant difference between topical and other oral antibiotics for limited disease, but oral therapy is preferred when lesions are numerous to reduce transmission 1.

Avoid penicillin for empiric therapy: Penicillin alone is inferior to other antibiotics (inferior to erythromycin RR 1.29, and to cloxacillin RR 1.59) because most impetigo is caused by S. aureus, which produces penicillinase 2.

Common Pitfalls to Avoid

• Don't use topical antibiotics for extensive disease - oral therapy is more practical and helps reduce community transmission 1
• Don't prescribe penicillin empirically - it's only appropriate when cultures confirm streptococcal infection alone 1
• Be aware of local resistance patterns - increasing resistance to mupirocin, fusidic acid, and erythromycin has been reported globally 4, 5
• Avoid erythromycin as first-line - resistance rates are high in both S. aureus and S. pyogenes 1

Special Circumstances

During outbreaks of post-streptococcal glomerulonephritis: Use systemic antimicrobials to help eliminate nephritogenic strains of S. pyogenes from the community 1.

Ecthyma (deeper infection): Always requires oral antibiotics rather than topical therapy, using the same agents as for extensive impetigo 1.

Side effects: Oral antibiotics cause more side effects than topical agents, primarily gastrointestinal symptoms 2. Topical therapy has minimal adverse effects and should be maximized when appropriate.