Bactrim Dosing for Skin Cyst
For an infected skin cyst, the recommended dose of Bactrim (trimethoprim-sulfamethoxazole) is 1-2 double-strength tablets (160 mg trimethoprim/800 mg sulfamethoxazole) orally twice daily for approximately 7 days. 1
Adult Dosing
The Clinical Infectious Diseases Society of America guidelines for skin and soft-tissue infections specify:
- Standard dose: 1 or 2 double-strength tablets twice per day orally 1
- Duration: Approximately 7 days, depending on clinical response 1
- Dosing basis: 8-12 mg/kg/day based on the trimethoprim component, given in either 4 divided doses IV or 2 divided doses orally 1
Pediatric Dosing
For children with skin and soft-tissue infections:
- Dose: 8-12 mg/kg/day (based on the trimethoprim component) 1
- Frequency: Either 4 divided doses IV or 2 divided doses orally 1
- Note: Doses are not appropriate for neonates; refer to specialized pediatric infectious disease references 1
Clinical Context and Considerations
When to use Bactrim for skin cysts:
- Bactrim is bactericidal and appropriate for both methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant Staphylococcus aureus (MRSA) skin infections 1
- It is particularly useful for purulent skin infections where MRSA is suspected 2
- Clinical improvement should be evident within 48-72 hours of initiating therapy 2
Important caveats:
- The guidelines note that efficacy data for Bactrim in skin infections is "poorly documented" or "limited" compared to other agents 1
- If no improvement occurs within 48-72 hours, consider possible antibiotic resistance or the need for incision and drainage if abscess formation has occurred 2
- Bactrim is contraindicated in pregnant women in the third trimester 2
Alternative Agents
If Bactrim is not tolerated or contraindicated, alternatives for skin and soft-tissue infections include:
- Clindamycin: 300-450 mg orally three times daily 2
- Doxycycline: 100 mg orally twice daily 1, 2
- Dicloxacillin: 500 mg four times daily (for MSSA only) 1