What antibiotics are used to treat skin infections?

Antibiotics for Skin Infections

For uncomplicated skin and soft tissue infections, first-line oral antibiotics include cephalexin (500 mg four times daily), dicloxacillin (500 mg four times daily), or clindamycin (300-450 mg three times daily), with selection based on suspected pathogens and local MRSA prevalence. 1

Impetigo and Superficial Infections

• Oral therapy for 7 days with dicloxacillin 250 mg four times daily or cephalexin 250 mg four times daily is recommended for impetigo when systemic treatment is needed 2, 1
• Topical mupirocin ointment applied three times daily is an alternative for localized disease 1
• When MRSA is suspected or confirmed, use doxycycline, clindamycin, or trimethoprim-sulfamethoxazole 2
• If cultures yield streptococci alone, oral penicillin is the preferred agent 2

Cellulitis and Erysipelas

Mild Cellulitis (No Systemic Signs)

• Target streptococci with cephalexin 500 mg every 6 hours or dicloxacillin 2
• Treat for 5 days minimum, extending if not improved 2

Moderate Cellulitis (With Fever or Systemic Signs)

• Many clinicians include MSSA coverage with cephalexin or dicloxacillin 2
• Consider MRSA coverage if penetrating trauma, purulent drainage, known MRSA colonization, injection drug use, or systemic inflammatory response syndrome (SIRS) present 2

Severe Cellulitis (MRSA Risk Factors or SIRS)

• Vancomycin 15 mg/kg every 12 hours IV or another agent effective against both MRSA and streptococci 2
• For severely immunocompromised patients, use broad-spectrum coverage: vancomycin plus piperacillin-tazobactam or a carbapenem 2

Abscesses and Furuncles

• Incision and drainage is the primary treatment; systemic antibiotics usually unnecessary unless fever or systemic infection present 2
• If antibiotics indicated, obtain cultures and treat with a 5-10 day course active against the isolated pathogen 2
• For MRSA abscesses requiring antibiotics: trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily, doxycycline 100 mg twice daily, or clindamycin 1

Bite Wounds (Animal or Human)

• Amoxicillin-clavulanate 875/125 mg twice daily orally is the recommended first-line agent 1
• IV option: ampicillin-sulbactam 1.5-3.0 g every 6-8 hours 1
• These provide coverage for both aerobic and anaerobic bacteria 2

Necrotizing Infections

• Urgent surgical debridement is mandatory 2
• Empiric broad-spectrum therapy: vancomycin plus piperacillin-tazobactam, ampicillin-sulbactam, or a carbapenem 2
• For documented group A streptococcal necrotizing fasciitis: penicillin 2-4 million units every 4-6 hours IV plus clindamycin 600-900 mg every 8 hours IV 2

MRSA-Specific Oral Options

• Linezolid 600 mg twice daily 1
• Trimethoprim-sulfamethoxazole 1-2 double-strength tablets twice daily 1
• Doxycycline 100 mg twice daily (avoid in children under 8 years) 1
• Clindamycin 300-450 mg three times daily 1

MSSA-Specific Options

• Nafcillin or oxacillin 1-2 g every 4 hours IV 1
• Dicloxacillin 500 mg four times daily orally 1
• Cefazolin 1 g every 8 hours IV 2

Pediatric Dosing

• Cephalexin: 25-50 mg/kg/day in divided doses 3
• For streptococcal pharyngitis and skin infections, may divide total daily dose every 12 hours 3
• For otitis media, 75-100 mg/kg/day in 4 divided doses required 3
• For β-hemolytic streptococcal infections, treat for at least 10 days to prevent rheumatic fever 1, 3

Critical Pitfalls to Avoid

• Do not rely on antibiotics alone for abscesses—drainage is essential 2
• Examine interdigital toe spaces in lower extremity cellulitis; treating tinea pedis reduces recurrence 2
• Obtain cultures for recurrent infections, treatment failures, or severe infections 1
• Local resistance patterns should guide empiric therapy—MRSA prevalence varies significantly by region 1
• Avoid cephalosporins as monotherapy when MRSA is suspected or confirmed 2