Amoxicillin Alone Is Not Recommended for Impetigo
Amoxicillin monotherapy should not be used for impetigo because it lacks adequate coverage against Staphylococcus aureus, which is now the predominant causative organism. 1, 2
Why Amoxicillin Fails for Impetigo
- S. aureus is the most common cause of both bullous and non-bullous impetigo, and amoxicillin does not provide reliable anti-staphylococcal coverage 3, 4
- Plain penicillin (and by extension, amoxicillin without a beta-lactamase inhibitor) has been shown to be inferior to other antibiotics for treating impetigo 5
- The IDSA guidelines explicitly state that penicillin is seldom effective and should only be used when cultures confirm streptococci alone 1, 4
Recommended Oral Antibiotics Instead
First-Line Options for Methicillin-Susceptible S. aureus (MSSA):
- Cephalexin 25-50 mg/kg/day divided into 4 doses for 7 days is the preferred first-line oral antibiotic 2
- Dicloxacillin 25-50 mg/kg/day divided into 4 doses for 7 days is an equally effective alternative 1, 2
When MRSA Is Suspected or Confirmed:
- Clindamycin 20-30 mg/kg/day divided into 3 doses for 7 days 1, 2
- Sulfamethoxazole-trimethoprim (SMX-TMP) 8-12 mg/kg/day divided into 2 doses for 7 days 1, 2
- Doxycycline 2-4 mg/kg/day divided into 2 doses for 7 days (only for children >8 years old) 2
The Exception: Amoxicillin-Clavulanate
- Amoxicillin combined with clavulanic acid (amoxicillin-clavulanate) is acceptable because the beta-lactamase inhibitor provides anti-staphylococcal coverage 4, 6
- One study demonstrated that amoxicillin-clavulanate achieved 86% clinical cure rates for soft tissue infections including impetigo 6
- However, this combination is not listed as a first-line agent in current guidelines, which favor cephalexin or dicloxacillin 1, 2
Topical Therapy for Limited Disease
- Topical mupirocin or retapamulin twice daily for 5 days is highly effective for limited impetigo and may be superior to oral antibiotics 1, 5
- Topical therapy causes fewer side effects than oral antibiotics, particularly gastrointestinal symptoms 5
- Oral therapy is recommended when patients have numerous lesions or during outbreaks to decrease transmission 1
Critical Clinical Pitfalls
- Never use plain penicillin or amoxicillin for empiric treatment of impetigo—they are ineffective against S. aureus 1, 4, 5
- In areas with high MRSA prevalence, empiric therapy should cover MRSA until culture results are available 2, 7
- Erythromycin resistance rates are rising, making macrolides less reliable 2, 4
- The standard duration for oral antibiotic therapy is 7 days, not the shorter 5-day course used for topical agents 1, 2