Oral Antibiotic Treatment for Impetigo
For impetigo treatment, dicloxacillin or cephalexin is recommended as first-line oral therapy for 7 days, as most staphylococcal isolates are methicillin-susceptible. When MRSA is suspected or confirmed, doxycycline, clindamycin, or sulfamethoxazole-trimethoprim (SMX-TMP) should be used instead 1.
First-Line Oral Antibiotic Options
Methicillin-Susceptible Staphylococcus aureus (MSSA) Infections
- Dicloxacillin: 250 mg four times daily for adults; 12 mg/kg/day in 4 divided doses for children 1
- Cephalexin: 250 mg four times daily for adults; 25 mg/kg/day in 4 divided doses for children 1
- Cephalexin twice daily dosing has shown comparable efficacy to four times daily dosing and may improve compliance 2
When MRSA is Suspected or Confirmed
- Clindamycin: 300-450 mg three times daily for adults; 10-20 mg/kg/day in 3 divided doses for children 1
- Doxycycline: 100 mg twice daily (not recommended for children under 8 years) 1
- Sulfamethoxazole-trimethoprim (SMX-TMP): 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
Treatment Duration and Considerations
- Standard duration: 7-day regimen for impetigo and ecthyma 1
- Penicillin alone is not recommended due to high rates of resistance among S. aureus isolates 3, 2
- Erythromycin (250 mg four times daily) may be used but resistance rates are increasing 1, 3
Special Situations
- Streptococcal impetigo: If cultures yield streptococci alone, oral penicillin is the recommended agent 1
- Widespread lesions or outbreaks: Oral therapy is preferred over topical treatment to help decrease transmission 1
- Poststreptococcal glomerulonephritis risk: Systemic antimicrobials should be used during outbreaks to eliminate nephritogenic strains from the community 1
Clinical Pearls and Pitfalls
- Common pitfall: Using penicillin as monotherapy when S. aureus is likely present. Studies show only 2 of 64 staphylococcal strains were susceptible to penicillin G in one study 2
- Compliance consideration: Twice-daily regimens (like cephalexin) may enhance compliance compared to four-times-daily regimens 2
- Resistance concerns: Monitor local resistance patterns as rates of resistance to erythromycin and other antibiotics are increasing 3
- Treatment failure: If no improvement is seen within 48-72 hours, consider obtaining cultures to guide therapy or switching to an alternative agent 3
Evidence Quality and Recommendations
The strongest evidence supports the use of dicloxacillin or cephalexin for MSSA, and clindamycin, doxycycline, or SMX-TMP for MRSA 1. The 2014 IDSA guidelines provide the most recent and comprehensive recommendations for impetigo treatment, emphasizing the importance of covering both S. aureus and streptococci unless cultures prove otherwise 1.