What are the clinical indications for Septran DS (trimethoprim‑sulfamethoxazole)?

Clinical Indications for Septran DS (Trimethoprim-Sulfamethoxazole)

Septran DS is indicated for urinary tract infections, Pneumocystis jirovecii pneumonia (treatment and prophylaxis), acute otitis media in children, acute exacerbations of chronic bronchitis, shigellosis, MRSA skin infections, traveler's diarrhea, and nocardiosis. 1

FDA-Approved Indications

Urinary Tract Infections

• Uncomplicated cystitis in women: Prescribe 1 DS tablet (160 mg trimethoprim/800 mg sulfamethoxazole) twice daily for 3 days when local E. coli resistance is <20%. 2, 3
• Uncomplicated cystitis in men: Prescribe 1 DS tablet twice daily for 7 days (the 3-day regimen used in women is insufficient for men). 2, 4
• Acute uncomplicated pyelonephritis: Prescribe 1 DS tablet twice daily for 14 days after confirming susceptibility. 2, 4
• Septran DS is effective against Escherichia coli, Klebsiella species, Enterobacter species, Morganella morganii, Proteus mirabilis, and Proteus vulgaris. 1

Pneumocystis jirovecii Pneumonia (PCP)

• Treatment of documented PCP: Septran DS is the drug of choice for active Pneumocystis infection. 1, 5
• Prophylaxis in HIV-infected adults: Prescribe 1 DS tablet daily when CD4+ count falls below 200 cells/µL, or with unexplained fever >100°F for ≥2 weeks, or with oropharyngeal candidiasis. 6, 2
• Prophylaxis in HIV-infected children: Begin at 4-6 weeks of age and continue through the first year of life for children born to HIV-infected mothers. 6
• Septran DS provides cross-protection against toxoplasmosis and many bacterial infections when used for PCP prophylaxis. 6

Respiratory Tract Infections

• Acute exacerbations of chronic bronchitis: Prescribe 1 DS tablet twice daily for susceptible strains of Streptococcus pneumoniae or Haemophilus influenzae when Septran DS offers advantage over single-agent therapy. 1, 7
• Acute otitis media in children: Use for susceptible S. pneumoniae or H. influenzae when preferred over other antimicrobials, particularly in penicillin-allergic patients or beta-lactamase-producing H. influenzae infections. 1, 8

Gastrointestinal Infections

• Shigellosis: Treat enteritis caused by susceptible Shigella flexneri and Shigella sonnei when antibacterial therapy is indicated. 1
• Traveler's diarrhea in adults: Use for susceptible enterotoxigenic E. coli. 1

Skin and Soft Tissue Infections

• MRSA skin infections: Prescribe 1-2 DS tablets twice daily for approximately 7 days; the higher dose (2 DS tablets) is reserved for more severe disease, though standard dosing (1 DS tablet twice daily) achieves similar clinical resolution rates (73-75%). 2, 9
• Critical caveat: Do not use Septran DS as monotherapy for non-purulent cellulitis due to poor activity against streptococci. 2

Other Infections

• Nocardiosis: Septran DS is effective for most Nocardia asteroides infections, either alone or combined with other antimicrobials. 5, 7
• Prostatitis: Useful for bacterial prostatitis caused by susceptible organisms. 7

Absolute Contraindications

• Documented sulfonamide allergy 4
• Third trimester of pregnancy (risk of kernicterus in the infant) 2, 4
• Marked hepatic impairment 4
• Creatinine clearance <15 mL/min without dose adjustment 4

Critical Resistance Threshold

• Do not prescribe Septran DS empirically when local E. coli resistance is ≥20%, as treatment failures outweigh benefits (cure rates drop from 90-100% with susceptible organisms to 41-54% with resistant organisms). 3, 4
• Avoid empiric use in patients who received Septran DS within the preceding 3-6 months or who traveled internationally within 3-6 months, as these factors predict resistance. 3, 4

Renal Dose Adjustments

• CrCl >30 mL/min: Standard dose (1 DS tablet twice daily) 4
• CrCl 15-30 mL/min: Reduce dose by 50% (use 1 single-strength tablet or half a DS tablet twice daily) 2, 4
• Monitor serum creatinine, electrolytes, and potassium 2-3 times weekly during therapy in renally impaired patients, as trimethoprim can cause hyperkalemia. 4

Common Adverse Effects

• Rash, urticaria, pruritus (most frequent dermatologic reactions) 2, 4
• Gastrointestinal intolerance (nausea, vomiting) occurs in 24-38% of patients 2, 8
• Hematologic abnormalities (thrombocytopenia, neutropenia, leukopenia) require monitoring of complete blood count during prolonged therapy 2, 4
• Adverse reactions occur in 40-65% of HIV-infected adults on daily PCP prophylaxis, though most are mild 2

Monitoring Requirements

• Complete blood count, renal function, and liver enzymes during prolonged therapy to detect hematologic or hepatic toxicity early 2
• Ensure adequate hydration (≥1.5 L/day) to reduce crystalluria risk 4