TMP-SMX Dosing for Wound Infections
For wound infections, the recommended dose of trimethoprim-sulfamethoxazole (TMP-SMX) is 160 mg trimethoprim/800 mg sulfamethoxazole (one double-strength tablet) twice daily orally, or 320 mg/1600 mg twice daily for more severe infections. 1
Standard Dosing Regimens
Outpatient Wound Infections
- TMP-SMX 160-800 mg (1-2 double-strength tablets) orally twice daily for uncomplicated skin and soft tissue infections 1
- This dosing provides good tissue penetration with mean tissue/serum ratios of 1.2 for trimethoprim 2
- Duration is typically 7-10 days for simple wound infections 1, 3
Surgical Site Infections
- TMP-SMX 160-800 mg orally every 6 hours for infections involving the trunk or extremities (away from axilla/perineum) 1
- This higher frequency dosing may be considered for more complex surgical site infections requiring systemic therapy
Evidence-Based Efficacy
MRSA Coverage
- TMP-SMX demonstrates bactericidal activity against both methicillin-resistant and methicillin-sensitive Staphylococcus aureus in wound infections 2
- In a randomized trial of 401 patients with uncomplicated wound infections, TMP-SMX 320/1600 mg twice daily achieved a 91.9% cure rate at 7-14 days 3
- For drained skin abscesses, TMP-SMX resulted in an 80.5% clinical cure rate compared to 73.6% with placebo (P=0.005) 4
Duration Considerations
- 10 days of therapy is superior to 3 days for MRSA wound infections, with significantly lower failure rates (10.1% difference, P=0.03) and reduced 1-month recurrence (10.3% difference, P=0.046) 5
- Standard 7-day courses are appropriate for uncomplicated infections 3, 4
Important Caveats
Coverage Limitations
- TMP-SMX has poor activity against anaerobes and should not be used as monotherapy for infections involving the axilla, perineum, or following intestinal/genitourinary surgery 1
- No activity against β-hemolytic streptococci in some contexts, though one study showed bactericidal activity 2
- For bite wounds (animal or human), TMP-SMX must be combined with metronidazole or another agent to cover anaerobes 1
When to Avoid TMP-SMX Monotherapy
- Infections near the axilla or perineum require addition of metronidazole 250-500 mg four times daily 1
- Surgical site infections following intestinal/genitourinary procedures need broader coverage 1
- Consider alternative agents (clindamycin, linezolid) if streptococcal infection is suspected 1
Comparative Effectiveness
- Clindamycin and TMP-SMX produce similar cure rates (92.1% vs 91.9%) but clindamycin shows lower recurrence rates (2.0% vs 7.1% at 6-8 weeks, P<0.05) 3
- This suggests TMP-SMX may be slightly inferior for preventing recurrent infections despite similar initial cure rates 3