Impetigo Treatment for Adults
For otherwise healthy adults with impetigo, treat localized disease with topical mupirocin 2% or retapamulin 1% twice daily for 5 days, and reserve oral antibiotics (dicloxacillin or cephalexin for 7 days) for extensive disease, numerous lesions, or when topical therapy fails. 1
Treatment Algorithm
Step 1: Assess Disease Extent
- Limited/localized lesions (few lesions, confined area): Topical therapy is first-line
- Extensive disease (numerous lesions, multiple body areas): Oral therapy recommended
- Outbreak setting (multiple people affected): Oral therapy preferred to reduce transmission 1
Step 2: Choose Appropriate Therapy
For Limited Disease - Topical Options:
- Mupirocin 2% ointment twice daily for 5 days (strong evidence) 1
- Retapamulin 1% ointment twice daily for 5 days (strong evidence) 1
- Both are equally effective as oral antimicrobials for impetigo 1, 2
For Extensive Disease - Oral Options:
First-line (methicillin-susceptible S. aureus expected):
These target both S. aureus and streptococci, which are the primary pathogens 1
If MRSA suspected or confirmed:
- Doxycycline for 7 days 1
- Clindamycin for 7 days 1
- Trimethoprim-sulfamethoxazole (TMP-SMX) for 7 days 1
If cultures yield streptococci alone:
- Penicillin is the drug of choice 1
Step 3: Consider Culture
While Gram stain and culture are recommended to identify whether S. aureus and/or β-hemolytic Streptococcus is the cause, treatment without cultures is reasonable in typical cases 1. Culture is most useful when:
- MRSA is suspected based on local resistance patterns
- Treatment failure occurs
- Outbreak situations require epidemiologic tracking
Important Clinical Considerations
When to Choose Oral Over Topical:
- Numerous lesions present
- Outbreak affecting multiple people (to decrease transmission)
- Ecthyma (deeper infection) - always requires oral therapy 1
- Failure to respond to topical therapy within 3-5 days 2
Antibiotic Resistance Concerns:
Most staphylococcal isolates from impetigo are methicillin-susceptible, making dicloxacillin and cephalexin appropriate first-line choices 1. However, increasing MRSA prevalence means you should consider local resistance patterns when selecting empiric therapy 3. Penicillin alone is NOT adequate as it lacks coverage for S. aureus 3.
Common Pitfalls to Avoid:
- Don't use penicillin as monotherapy unless cultures confirm streptococci alone 1
- Don't use topical disinfectants - they are inferior to antibiotics 3
- Don't delay oral therapy in extensive disease thinking topical will suffice
- Don't forget transmission precautions - patients should avoid work/school until 12-24 hours after starting antibiotics 2
Natural History Context
Without treatment, approximately 13-74% of patients show resolution by 7 days, though about one-quarter fail to improve 4. However, antibiotic treatment is typically initiated to reduce spread, shorten clinical course, and prevent rare complications like post-streptococcal glomerulonephritis 1, 5.