What is the first‑line oral medication and dosing for a generally healthy child with impetigo, and what alternatives are recommended for penicillin allergy or MRSA concern?

Oral Pediatric Impetigo Treatment

First-Line Oral Antibiotic Therapy

For generally healthy children with impetigo, oral cephalexin (cefalexin) at 40–50 mg/kg/day divided into three doses for 7–10 days is the most effective first-line oral treatment, with oral erythromycin 30–40 mg/kg/day in three divided doses as a nearly equally effective and more cost-effective alternative. 1, 2

Primary Oral Antibiotic Options

• Cephalexin (cefalexin): 40–50 mg/kg/day divided into three doses for 7–10 days demonstrates superior efficacy with 0% treatment failure rates in clinical trials 2
• Erythromycin: 30–40 mg/kg/day divided into three doses for 7–10 days shows nearly equivalent effectiveness (4% treatment failure) and may be preferred based on cost-effectiveness 1, 2
• Dicloxacillin: Recommended by IDSA guidelines as an effective oral option, though specific pediatric dosing follows standard anti-staphylococcal penicillin protocols 1
• Amoxicillin-clavulanate: Listed as an acceptable oral option in IDSA guidelines for impetigo treatment 1

Avoid Penicillin V

• Penicillin V is inadequate: Shows 24% treatment failure rates and should not be used as monotherapy for impetigo, as it is inferior to both erythromycin and cephalosporins 1, 3, 2

Penicillin Allergy Alternatives

For children with penicillin allergy, oral clindamycin 30–40 mg/kg/day divided into 3–4 doses is the preferred single agent because it provides coverage against both β-hemolytic streptococci and Staphylococcus aureus. 1, 4

Clindamycin Dosing Specifics

• Standard oral dose: 30–40 mg/kg/day divided into 3–4 doses for 7–10 days 1, 4
• Maximum daily dose: Do not exceed 40 mg/kg/day total 1, 4
• Resistance consideration: Only use clindamycin when local MRSA clindamycin resistance rates are <10% 1, 4
• D-zone testing: Perform testing on erythromycin-resistant isolates to detect inducible clindamycin resistance before initiating therapy 4

Alternative Options for Penicillin Allergy

• Erythromycin: 30–40 mg/kg/day in three divided doses remains effective if macrolide resistance rates are low 1, 2
• Trimethoprim-sulfamethoxazole: Can be used for community-acquired MRSA infections in well children, though close monitoring for adverse effects is required 5

MRSA-Specific Treatment

When MRSA is confirmed or highly suspected, oral clindamycin 30–40 mg/kg/day divided into 3–4 doses is the preferred oral agent for stable children without bacteremia. 1, 4, 5

MRSA Treatment Algorithm

• Community-acquired MRSA in well children: Clindamycin 30–40 mg/kg/day divided into 3–4 doses OR trimethoprim-sulfamethoxazole with close monitoring 1, 5
• Resistance screening: Check local resistance patterns before empiric clindamycin use; only employ when resistance <10% 1, 4
• Severe MRSA infections: Require intravenous vancomycin and are beyond the scope of simple oral impetigo treatment 1, 5

Treatment Duration

• Standard course: 7–10 days is adequate for most cases, with no evidence that 10 days is superior to 7 days 5, 3, 2
• Clinical response: Most children show improvement within 48–72 hours; lack of response warrants culture and sensitivity testing 3, 6

Topical Therapy Consideration

• Localized lesions: Topical mupirocin 2% ointment three times daily may be sufficient for minor infections and is superior to oral antibiotics in some studies 1, 3, 6
• Extensive disease: Oral antibiotics should be considered when lesions are widespread or involve multiple body sites 3, 6, 7

Critical Pitfalls to Avoid

• Do not use penicillin V monotherapy: It shows significantly higher failure rates (24%) compared to cephalosporins (0%) and erythromycin (4%) 2
• Avoid topical disinfectants: There is no evidence supporting their use, and topical antibiotics are significantly more effective 1, 3, 6
• Monitor for rising erythromycin resistance: Macrolide resistance rates are increasing globally, potentially limiting erythromycin effectiveness 5, 3
• Ensure adequate dosing: Underdosing, particularly with cephalexin or clindamycin, risks treatment failure 4, 2