Tab Septran DS (Trimethoprim-Sulfamethoxazole) Dosing
For a typical adult patient without specified medical history, the standard dosing of Septran DS (double-strength tablet containing 160 mg trimethoprim/800 mg sulfamethoxazole) is one tablet twice daily for most common infections. 1
Standard Adult Dosing by Indication
Urinary Tract Infections
- One DS tablet every 12 hours for 10-14 days is the FDA-approved regimen for uncomplicated UTIs 1
- This provides 320 mg trimethoprim and 1600 mg sulfamethoxazole daily 1
Skin and Soft Tissue Infections (including MRSA)
- 1-2 DS tablets twice daily for typically 7 days based on clinical response 2
- The Infectious Diseases Society of America supports this dosing range for purulent cellulitis where MRSA is suspected 2
- Critical caveat: Septran has poor activity against beta-hemolytic streptococci, so avoid using it alone for non-purulent cellulitis 2
Acute Exacerbations of Chronic Bronchitis
- One DS tablet every 12 hours for 14 days 1
Traveler's Diarrhea
- One DS tablet every 12 hours for 5 days 1
Shigellosis
- One DS tablet every 12 hours for 5 days 1
Alternative Dosing Schedules
Prophylactic Regimens (e.g., PCP prophylaxis in immunocompromised patients)
- One DS tablet daily is the standard prophylactic dose 1
- Alternative: One DS tablet three times weekly on consecutive days (e.g., Monday-Tuesday-Wednesday) 3, 4
- The three-times-weekly regimen provides equivalent protection with potentially fewer side effects 4
Renal Dose Adjustments
Dose reduction is mandatory when creatinine clearance falls below 30 mL/min 1:
- CrCl >30 mL/min: Use standard dosing 1
- CrCl 15-30 mL/min: Use half the usual dose 1
- CrCl <15 mL/min: Use is not recommended by FDA labeling 1, though for prophylaxis specifically, 500 mg three times weekly after dialysis is acceptable 4
Critical Safety Considerations
Absolute Contraindications
- Third trimester pregnancy due to kernicterus risk 2
- Nursing mothers 2
- Sulfa allergies 2
- G6PD deficiency due to hemolytic anemia risk 4
- Infants less than 2 months of age 1
Drug Interactions
- Avoid concurrent use with methotrexate at treatment doses due to severe bone marrow suppression risk 4
- Lower prophylactic methotrexate doses are generally tolerated 4
Monitoring Requirements
- Obtain baseline hemogram and monitor monthly for hematological toxicity, particularly thrombocytopenia 4
- Most adverse reactions develop within two weeks of therapy initiation 5
Common Pitfalls to Avoid
- Do not use as monotherapy for mixed aerobic-anaerobic wound infections as it lacks anaerobic coverage 2
- Do not use alone for non-purulent cellulitis where streptococci are likely pathogens 2
- Do not forget renal dose adjustment when CrCl <30 mL/min, as both components are renally excreted 6
- Recent pharmacokinetic data suggests the guideline-recommended 90 mg/kg/day dose for severe infections may cause supratherapeutic exposure in patients with normal renal function 7