What is the recommended treatment for a patient with impetigo, considering severity and potential allergies to oral antibiotics?

Treatment of Impetigo

For limited impetigo, topical mupirocin 2% ointment applied three times daily for 5-7 days is first-line treatment, while extensive disease, systemic symptoms, or lesions on the face/mouth require oral antibiotics such as cephalexin or dicloxacillin for 7-10 days. 1, 2

Initial Assessment and Treatment Selection

The choice between topical and oral antibiotics depends on disease extent and clinical presentation:

Topical therapy is appropriate when:

• Limited number of lesions are present 1
• No systemic symptoms exist 1
• Lesions are not on the face, eyelid, or mouth 1
• Patient can comply with three-times-daily application 1

Oral antibiotics are required when:

• Disease is extensive 1
• Systemic symptoms are present 1
• Lesions involve the face, eyelid, or mouth 1
• No improvement occurs after 3-5 days of topical therapy 3, 1
• There is need to limit spread to others (e.g., during outbreaks) 1

Topical Antibiotic Therapy

Mupirocin 2% ointment is the most effective topical agent, applied three times daily for 5-7 days. 1, 2 The FDA label confirms mupirocin is indicated for impetigo caused by Staphylococcus aureus and Streptococcus pyogenes, with clinical efficacy rates of 71-93% in controlled trials. 2

Important caveats:

• Bacitracin and neomycin are considerably less effective and should not be used 1
• Topical clindamycin cream lacks FDA indication for impetigo and should not be used, as it is formulated for acne with insufficient bioavailability for bacterial skin infections 1
• Mupirocin resistance has been increasingly documented, especially in areas with high MRSA prevalence 4

Oral Antibiotic Selection

For Presumed Methicillin-Susceptible S. aureus (MSSA):

First-line options:

• Dicloxacillin: 250 mg four times daily for adults; 12 mg/kg/day in 4 divided doses for children 1, 4
• Cephalexin: 250-500 mg four times daily for adults; 25 mg/kg/day in 4 divided doses for children 1, 4
• Amoxicillin-clavulanate: 875/125 mg twice daily for adults; 25 mg/kg/day of amoxicillin component in 2 divided doses for children 4

Duration: 7-10 days 1

For Suspected or Confirmed MRSA:

Preferred options:

• Clindamycin: 300-450 mg three times daily for adults; 10-20 mg/kg/day in 3 divided doses for children 1, 4
• Trimethoprim-sulfamethoxazole (TMP-SMX): 1-2 double-strength tablets twice daily for adults; 8-12 mg/kg/day (based on trimethoprim component) in 2 divided doses for children 1, 4
• Doxycycline: 100 mg twice daily for adults (not for children under 8 years) 4

Critical warning: TMP-SMX should not be used as monotherapy if Streptococcus pyogenes is suspected, as it lacks adequate streptococcal coverage. 3 Penicillin alone is not effective for impetigo due to inadequate S. aureus coverage. 1

Special Populations and Allergy Considerations

For penicillin-allergic patients:

• Clindamycin is the preferred alternative 1
• Avoid cephalosporins if type 1 hypersensitivity (anaphylaxis/hives) to β-lactams exists 1

For pregnant patients:

• Cephalexin is generally considered safe 4
• Avoid tetracyclines 4

For children under 8 years:

• Avoid doxycycline and other tetracyclines 1, 4

For immunocompromised patients:

• Use a lower threshold for oral antibiotics 1
• Monitor closely for treatment failure or deeper infection 1
• Consider longer treatment duration based on clinical response 1

Treatment Failure Management

If no improvement occurs by 3-5 days of appropriate therapy, reassess for: 1

• MRSA infection requiring alternative antibiotics 1
• Mupirocin resistance (especially in high MRSA prevalence areas) 4
• Deeper or more complex infection than initially estimated 1
• Non-compliance with therapy 1
• Alternative diagnosis 4

For impetigo refractory to mupirocin:

• Switch to oral antibiotics (dicloxacillin, cephalexin, clindamycin, or amoxicillin-clavulanate) 4
• Consider obtaining cultures if treatment failure occurs or MRSA is suspected 1, 4

Culture Indications

Cultures are not routinely necessary for typical cases of limited impetigo, but should be obtained when: 1

• Treatment failure occurs 1
• MRSA is suspected 1
• Recurrent infections develop 1
• Patient is immunocompromised 1

Prevention and Infection Control

For athletes and organized sports:

• Exclude from participation until 24 hours after initiation of effective antimicrobial therapy 3
• Skin lesions must be covered with clean, dry bandages 1
• Maintain good personal hygiene with regular handwashing 1
• Avoid sharing personal items that contact the skin 1

During outbreaks:

• Systemic antimicrobials should be used to help eliminate nephritogenic strains of S. pyogenes from the community 1
• Consider decolonization strategies using topical nasal mupirocin therapy (twice daily for 5-7 days) for S. aureus carriers 3