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

Impetigo Treatment

For limited impetigo (few lesions), use topical mupirocin 2% ointment twice daily for 5 days; for extensive disease or when topical therapy fails, prescribe oral cephalexin or dicloxacillin for 7 days, switching to clindamycin or trimethoprim-sulfamethoxazole if MRSA is suspected. 1, 2, 3

Treatment Algorithm Based on Disease Extent

Limited Disease (Few Lesions)

• Topical mupirocin 2% ointment applied twice daily for 5 days is first-line therapy and achieves cure rates 6-fold higher than placebo 3, 4
• Topical retapamulin 1% ointment applied twice daily for 5 days is an alternative for patients aged 9 months or older, covering up to 100 cm² in adults or 2% total body surface area in children 1, 5
• The treated area may be covered with a sterile bandage or gauze dressing 5

Extensive Disease (Numerous Lesions)

Oral antibiotics are required when patients have multiple lesions, during outbreaks to decrease transmission, or when topical therapy is impractical 1, 3

For presumed methicillin-susceptible S. aureus (MSSA):

• Cephalexin: 250-500 mg four times daily for adults; 25-50 mg/kg/day in 4 divided doses for children, for 7 days 1, 2, 3
• Dicloxacillin: 250 mg four times daily for adults; 25-50 mg/kg/day in 4 divided doses for children, for 7 days 1, 2, 3
• Amoxicillin-clavulanate: 875/125 mg twice daily for adults; 25 mg/kg/day (amoxicillin component) in 2 divided doses for children, for 7 days 1, 2, 3

For suspected or confirmed MRSA (especially in high-prevalence areas):

• Clindamycin: 300-450 mg three to four times daily for adults; 20-30 mg/kg/day in 3 divided doses for children, for 7 days 1, 2, 3
• Trimethoprim-sulfamethoxazole: 1-2 double-strength tablets twice daily for adults; 8-12 mg/kg/day (trimethoprim component) in 2 divided doses for children, for 7 days 1, 2, 3
• Doxycycline: 100 mg twice daily for adults and children over 8 years only, for 7 days 1, 2, 3

Management of Penicillin Allergy

For patients with penicillin allergy:

• Use cephalexin (first-generation cephalosporin) except in those with immediate hypersensitivity reactions 1
• Clindamycin is safe for all penicillin-allergic patients: 300-450 mg three to four times daily for adults; 20-30 mg/kg/day in 3 divided doses for children 1, 2
• Macrolides (erythromycin, clarithromycin) can be used but resistance rates are rising and should be used with caution 1, 3, 4

Treatment Failure and Mupirocin Resistance

If impetigo is refractory to mupirocin:

• Initiate oral antibiotics immediately (cephalexin, dicloxacillin, clindamycin, or amoxicillin-clavulanate) 2
• Consider mupirocin resistance, which has been increasingly documented, especially in high MRSA prevalence areas 2, 4
• Obtain cultures if treatment failure occurs or MRSA is suspected 2
• Re-evaluate if no improvement after 48-72 hours of oral therapy 2

Critical Treatment Considerations and Common Pitfalls

Avoid these common errors:

• Never use penicillin alone for impetigo—it lacks adequate coverage against S. aureus and is seldom effective 1, 3, 6
• Never use amoxicillin alone without clavulanate—it lacks adequate coverage against S. aureus 3
• Oral antibiotics require 7 days of treatment, not the shorter 5-day course used for topical agents 2, 3
• Topical disinfectants are inferior to antibiotics and should not be used as primary therapy 3, 6
• Avoid tetracyclines (doxycycline) in children under 8 years due to risk of permanent dental staining 2, 3

Special Populations

Pregnant patients:

• Cephalexin is generally considered safe 2, 3
• Avoid tetracyclines 2

Children under 8 years:

• Avoid doxycycline and other tetracyclines 1, 2, 3
• Clindamycin or trimethoprim-sulfamethoxazole are preferred for MRSA coverage 2, 3

Immunocompromised or diabetic patients:

• Have a lower threshold for systemic antibiotics and hospital admission if extensive disease or systemic signs are present 3

Infection Control Measures

To prevent spread and recurrence:

• Keep lesions covered with clean, dry bandages 3
• Maintain good personal hygiene with regular handwashing 3
• Avoid sharing personal items that contact the skin 3
• Clean high-touch surfaces that contact bare skin 3

Recurrent Impetigo

For recurrent cases:

• Consider decolonization strategies for S. aureus carriers 2
• Systemic antimicrobials should be used during outbreaks of poststreptococcal glomerulonephritis to eliminate nephritogenic strains 3