What type and duration of antibiotics are recommended for a patient with bullous impetigo?

Treatment of Bullous Impetigo

Recommended Antibiotic Type and Duration

For bullous impetigo, use oral cephalexin 25-50 mg/kg/day divided into 4 doses (or dicloxacillin at the same dosing) for 7 days as first-line therapy, switching to clindamycin or trimethoprim-sulfamethoxazole if MRSA is suspected. 1

Antibiotic Selection Algorithm

First-Line Therapy for Presumed MSSA

• Cephalexin is the preferred first-line oral antibiotic at 25-50 mg/kg/day divided into 4 doses for 7 days 1
• Dicloxacillin is an equally effective alternative at 25-50 mg/kg/day divided into 4 doses for 7 days 1
• Both agents demonstrated equal efficacy in treating staphylococcal bullous impetigo, with prompt clearing of lesions within the first week 2

MRSA Coverage When Indicated

• Clindamycin 20-30 mg/kg/day divided into 3 doses for 7 days should be used when MRSA is suspected or confirmed 1, 3
• Trimethoprim-sulfamethoxazole (SMX-TMP) 8-12 mg/kg/day (based on trimethoprim component) divided into 2 doses for 7 days is an alternative MRSA-covering option 1
• Doxycycline 2-4 mg/kg/day divided into 2 doses for 7 days can be used in children over 8 years old when MRSA is suspected 1

Alternative Oral Options

• Co-amoxiclav (amoxicillin-clavulanic acid) for 7 days is an acceptable alternative that covers both S. aureus and S. pyogenes 1
• This is particularly useful when dicloxacillin or cephalexin are not suitable 1

Critical Duration Point

The standard duration for oral antibiotic therapy is 7 days, not the shorter 5-day course used for topical agents. 1, 3

Important Clinical Considerations

Why Bullous Impetigo Requires Specific Therapy

• Bullous impetigo is exclusively caused by toxin-producing Staphylococcus aureus, unlike non-bullous impetigo which may involve Streptococcus pyogenes 1
• This makes anti-staphylococcal coverage essential 4

Antibiotics to Avoid

• Penicillin alone is seldom effective for impetigo and should only be used when cultures confirm streptococci alone 1
• Amoxicillin alone should not be used because it lacks adequate coverage against S. aureus 1
• Only 2 of 64 staphylococcal strains in one study were susceptible to penicillin G 2

When to Consider MRSA Coverage

• In areas with high MRSA prevalence, empiric therapy should cover MRSA until culture results are available 1
• Consider obtaining cultures if there is treatment failure, MRSA is suspected, or in cases of recurrent infections 3

Special Population Considerations

Pediatric Patients

• Tetracyclines (doxycycline) should be avoided in children under 8 years due to the risk of dental staining 1, 3

Pregnant Patients

• Cephalexin can be considered a safe alternative for pregnant patients 1, 3

Penicillin-Allergic Patients

• Clindamycin or macrolides can be used, though resistance rates to erythromycin are rising 1
• Avoid cephalosporins if type 1 hypersensitivity (anaphylaxis/hives) to β-lactams exists 3

Common Pitfalls to Avoid

• Do not use topical therapy alone for bullous impetigo with large bullae or extensive disease—oral antibiotics are required 4
• Do not assume 5 days is sufficient—the standard oral antibiotic duration is 7 days, not 5 1, 3
• Reassess by 3-5 days if no improvement occurs, considering MRSA infection, deeper infection, non-compliance, or antibiotic resistance 3