What is the appropriate antibiotic for impetigo on the neck after shaving in an adult with no drug allergies, not pregnant, and normal renal and hepatic function?

Topical Mupirocin for Limited Impetigo, Oral Cephalexin for Extensive Disease

For impetigo on the neck from shaving in an adult with no allergies and normal organ function, use topical mupirocin 2% ointment applied twice to three times daily for 5-7 days if lesions are limited; if extensive or spreading, prescribe oral cephalexin 250-500 mg four times daily for 7 days. 1, 2

Treatment Algorithm Based on Disease Extent

Limited Disease (Few Lesions)

• Topical mupirocin 2% ointment is the first-line treatment, applied twice to three times daily for 5-7 days 1, 2
• Topical therapy achieves cure rates 6-fold higher than placebo and is superior to oral antibiotics for limited impetigo 1
• Retapamulin 1% ointment twice daily for 5 days is an acceptable alternative 1, 2

Extensive Disease or When Topical Therapy is Impractical

• Oral cephalexin 250-500 mg four times daily for 7 days is the recommended first-line systemic antibiotic 1, 2
• Alternative first-line agents include dicloxacillin 250 mg four times daily for 7 days or amoxicillin-clavulanate 1, 2
• The liquid suspension formulation and simpler dosing schedule make cephalexin more practical than dicloxacillin 1

When to Suspect MRSA and Adjust Therapy

Switch from cephalexin to MRSA-active therapy if:

• Lesions exhibit purulent drainage 1
• Prior standard treatment has failed 1
• Local community-acquired MRSA prevalence exceeds 10% 1

MRSA-Active Oral Options (7-10 days)

• Clindamycin 300-450 mg three to four times daily when local clindamycin resistance is <10% 1, 2
• Trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily, though this does not reliably cover streptococcal infection when used alone 1, 2
• Doxycycline 100 mg twice daily is effective but should be avoided in children under 8 years 1, 2

Critical Pitfalls to Avoid

• Do not prescribe oral antibiotics for limited disease when topical mupirocin is appropriate and more effective 1
• Do not use cephalexin or any beta-lactam when MRSA is documented or strongly suspected, as these agents lack MRSA activity 1
• Do not shorten oral therapy to less than 7 days, as shorter courses increase failure and recurrence risk 1
• Do not use penicillin alone, as it is seldom effective for impetigo and should only be used when cultures confirm streptococci alone 1, 3
• Do not rely on macrolides (erythromycin, azithromycin), as resistance rates are rising and these agents are no longer reliably effective 1, 2

Infection Control Measures

Concurrent hygiene interventions are essential alongside antimicrobial therapy:

• Keep draining lesions covered with clean, dry dressings 1
• Perform regular hand hygiene with soap and water or alcohol-based hand rubs 1
• Do not share personal items that contact skin (razors, towels, linens) 1
• Clean high-touch surfaces that may contact bare skin 1

Evidence Quality Considerations

The Infectious Diseases Society of America and American Academy of Pediatrics guidelines provide the strongest evidence base for these recommendations 1. The superiority of topical mupirocin over oral antibiotics for limited disease is supported by high-quality evidence showing 6-fold higher cure rates 1. For extensive disease, cephalexin provides reliable coverage for both Staphylococcus aureus and Streptococcus pyogenes, the two primary causative organisms in non-bullous impetigo 1, 3.