Oral Antibiotics for MRSA Skin Infections
Trimethoprim-sulfamethoxazole (TMP-SMX) 1-2 double-strength tablets (160mg/800mg) twice daily for 7-10 days is the first-line oral antibiotic for MRSA skin infections. 1
Primary Treatment Principle
- Incision and drainage is the cornerstone of treatment for purulent MRSA infections, with antibiotics serving a subsidiary role. 1
- Antibiotics should be added when systemic signs are present, extensive surrounding cellulitis exists, multiple lesions are present, the patient is immunocompromised, or drainage alone has failed. 1
- Always obtain culture from purulent drainage before starting antibiotics to confirm MRSA and guide definitive therapy. 1
First-Line Oral Antibiotic Options
TMP-SMX (Trimethoprim-Sulfamethoxazole):
- Dose: 1-2 double-strength tablets (160mg/800mg) twice daily for 7-10 days. 1
- This is the most effective oral option for MRSA coverage according to the Infectious Diseases Society of America. 1
- Limitation: Does not cover β-hemolytic streptococci, so if streptococcal infection is suspected, consider alternative agents. 2
- Clinical studies demonstrate high cure rates for community-acquired MRSA skin infections. 3, 4
Doxycycline:
- Dose: 100 mg twice daily for 7-10 days. 1
- Use as an alternative when TMP-SMX fails or is contraindicated. 1
- Contraindicated in children under 8 years of age due to tooth discoloration and bone growth effects. 1, 2
- Contraindicated in pregnancy (category D). 1
- Note: Minocycline may be more reliably effective than doxycycline when initial therapy fails. 5
Clindamycin:
- Dose: 300-450 mg every 6 hours (or three times daily) for 7-10 days. 1, 2
- Preferred when coverage for both MRSA and β-hemolytic streptococci is needed. 1
- Critical caveat: Only use if local clindamycin resistance is <10%. 1
- Advantage: Provides dual coverage for both MRSA and streptococcal species. 2
- For pediatric patients, dose is 10-20 mg/kg/day in 3 divided doses. 2
Second-Line Option for Severe or Refractory Cases
Linezolid:
- Dose: 600 mg orally twice daily. 2, 6
- Reserved for serious infections or when other options fail. 2
- Advantage: No cross-resistance with other antibiotic classes and excellent MRSA coverage. 2
- Limitation: High cost limits routine use. 2
- FDA data shows 79% cure rate for MRSA skin infections. 6
Treatment Duration
- Standard duration: 5-10 days for uncomplicated MRSA skin infections. 2
- The Infectious Diseases Society of America recommends 5 days if clinical improvement occurs, extending only if symptoms have not improved. 1
- For complicated infections: 7-14 days. 2
- Reassess clinically within 48-72 hours to ensure appropriate response. 1
Special Population Considerations
Pregnancy:
- Avoid doxycycline (pregnancy category D). 1
- Use clindamycin or TMP-SMX after the first trimester as safer alternatives. 1
Pediatric Patients:
- Clindamycin 10-13 mg/kg/dose every 6-8 hours is preferred. 1
- Avoid doxycycline in children <8 years old. 1
- Mupirocin 2% topical ointment for minor infections. 2
Abdominal/Perineal Surgical Site Infections:
- Add metronidazole 500mg every 8 hours to TMP-SMX to cover anaerobic organisms. 7
- Never use TMP-SMX as monotherapy for polymicrobial abdominal wound infections without anaerobic coverage. 7
Critical Pitfalls to Avoid
- Do not use rifampin as a single agent or adjunctive therapy for MRSA skin infections. 2
- Do not rely on vancomycin for outpatient oral therapy—it is not available orally for systemic infections. 2
- Do not use β-lactam antibiotics (cephalexin, dicloxacillin) for confirmed MRSA as they are ineffective. 8
- Obtain cultures in patients receiving antibiotic therapy to guide treatment. 2