Can erythromycin be used to treat impetigo?

Can Erythromycin Be Used for Impetigo?

Erythromycin is no longer recommended as a first-line treatment for impetigo due to rising resistance rates among causative organisms, particularly Staphylococcus aureus, and should only be used with caution when other preferred agents are unavailable. 1

Current Guideline-Based Recommendations

The treatment hierarchy for impetigo has evolved significantly away from erythromycin:

First-Line Treatment for Limited Disease

• Topical mupirocin 2% ointment applied twice to three times daily for 5 days is the preferred first-line therapy for limited impetigo, achieving cure rates superior to oral antibiotics. 1, 2
• Retapamulin 1% ointment twice daily for 5 days is an acceptable alternative for patients aged 9 months or older. 1

First-Line Oral Antibiotics for Extensive Disease

When oral therapy is required (numerous lesions, topical therapy impractical, or during outbreaks):

• Cephalexin 25-50 mg/kg/day divided into 4 doses for 7 days is the recommended first-line oral antibiotic for presumed methicillin-susceptible S. aureus (MSSA). 1
• Dicloxacillin 25-50 mg/kg/day divided into 4 doses for 7 days is an equally effective alternative. 1
• Co-amoxiclav (amoxicillin-clavulanic acid) is an acceptable option when cephalexin or dicloxacillin are not suitable. 1

MRSA-Active Alternatives

When MRSA is suspected (purulent drainage, prior treatment failure, high local prevalence >10%):

• Clindamycin 20-30 mg/kg/day divided into 3 doses for 7 days 1
• Trimethoprim-sulfamethoxazole 8-12 mg/kg/day (trimethoprim component) divided into 2 doses for 7 days 1
• Doxycycline 2-4 mg/kg/day divided into 2 doses for 7 days (only for children >8 years) 1

Why Erythromycin Has Fallen Out of Favor

Rising Resistance Rates

• Macrolide agents including erythromycin and azithromycin show rising resistance rates in impetigo pathogens and should be used only with caution. 1
• This resistance pattern has fundamentally changed treatment recommendations over the past two decades.

Historical Efficacy Data

While older studies from 1988-1990 showed erythromycin had comparable efficacy to other agents at that time:

• One 1988 study found erythromycin (40 mg/kg/day) cured or improved 28 of 29 children with S. aureus impetigo, leading authors to conclude it was "the drug of choice" in their midwestern locale. 3
• A 1990 study showed erythromycin estolate (30-40 mg/kg/day) had only a 4% treatment failure rate compared to 24% with penicillin V, though cephalexin had 0% failure. 4
• Multiple 1988 studies demonstrated topical mupirocin was equal or superior to oral erythromycin. 5, 6, 7

However, these historical data are no longer applicable given current resistance patterns, and modern guidelines have moved away from erythromycin as a recommended agent.

Critical Pitfalls to Avoid

• Do not use erythromycin as first-line therapy when guideline-recommended agents (topical mupirocin, cephalexin, dicloxacillin) are available. 1
• Do not prescribe oral antibiotics for limited impetigo when topical mupirocin is appropriate and more effective. 1
• Do not assume erythromycin provides adequate coverage in areas with high MRSA prevalence or when MRSA is suspected. 1
• Do not shorten treatment duration below 7 days for oral antibiotics, as shorter courses increase failure and recurrence risk. 1

When Erythromycin Might Be Considered

If erythromycin must be used (due to allergy, cost, or availability constraints):

• Confirm susceptibility through culture when possible
• Use a 7-day course at 40-50 mg/kg/day divided into 4 doses (maximum 2 g/day) 8
• Monitor closely for treatment failure
• Be aware of gastrointestinal side effects (nausea, vomiting, abdominal pain, diarrhea), which are more frequent and severe with erythromycin than other macrolides 8

Practical Algorithm

1. For limited impetigo (<100 cm² total area): Use topical mupirocin 2% ointment twice daily for 5 days 1, 2
2. For extensive disease or when topical therapy fails: Use oral cephalexin 25-50 mg/kg/day divided into 4 doses for 7 days 1
3. If MRSA suspected: Switch to clindamycin, trimethoprim-sulfamethoxazole, or doxycycline (>8 years) 1
4. If penicillin/cephalosporin allergy (non-immediate): Cephalexin may still be used 1
5. If immediate hypersensitivity to beta-lactams: Use clindamycin 1
6. Erythromycin: Reserve only for situations where preferred agents are unavailable and resistance is documented as low 1