What is the recommended duration of Bactrim (trimethoprim/sulfamethoxazole) treatment for an infected cyst?

Treatment Duration of Bactrim for Infected Cysts

For infected cysts, Bactrim (trimethoprim-sulfamethoxazole) should be administered for 7-10 days at a dosage of one double-strength tablet (160 mg trimethoprim/800 mg sulfamethoxazole) orally twice daily. 1

Dosing Considerations

• The standard adult dose for skin and soft tissue infections, including infected cysts, is 1 double-strength tablet (160 mg trimethoprim/800 mg sulfamethoxazole) twice daily 1
• Treatment duration of 7-10 days is recommended for adequate eradication of the infection in soft tissue infections including cysts 1
• Clinical improvement should be evident within 48-72 hours of initiating therapy; if no improvement is seen, consider possible resistance or need for drainage 1

Efficacy and Resistance Considerations

• Bactrim efficacy is significantly reduced when treating infections caused by resistant organisms (84% cure rate with susceptible organisms vs. 41% with resistant organisms) 2, 3
• Local resistance patterns should be considered before prescribing Bactrim; it should only be used empirically when local resistance rates are below 20% 3
• For infected cysts, obtaining cultures before treatment is recommended whenever possible to guide appropriate antibiotic selection 3

Special Considerations for Cyst Infections

• Trimethoprim can accumulate in cyst fluid, exceeding serum levels by up to eightfold, particularly in gradient cysts, making it potentially effective for cyst infections 4, 5
• Sulfamethoxazole penetrates cysts to a lesser extent, with concentrations ranging from 10-70% of serum levels 4
• Prolonged therapy may be necessary to ensure therapeutic success in cyst infections 5

Alternative Treatment Options

• If Bactrim is not effective or contraindicated, alternative antibiotics include:
  • Clindamycin 300-450 mg orally three times daily 1
  • Doxycycline 100 mg orally twice daily 1
  • Linezolid 600 mg orally twice daily 1

Monitoring and Follow-up

• Complete the full course of antibiotics even if symptoms improve rapidly 1
• If fluctuance is present, incision and drainage should be performed in addition to antimicrobial therapy 1
• For recurrent or chronic infections, urine culture and susceptibility testing should be performed before initiating therapy 3

Common Pitfalls to Avoid

• Using Bactrim empirically in areas with high resistance rates (>20%) can lead to treatment failure 3
• Discontinuing treatment prematurely when symptoms improve can lead to recurrence 1
• Not considering drainage as an adjunct to antibiotic therapy when indicated 1