What is the dosage and duration of Bactrim DS (trimethoprim/sulfamethoxazole) for treating E. coli in urine with a Glomerular Filtration Rate (GFR) of 76?

Trimethoprim-Sulfamethoxazole (Bactrim DS) for E. coli UTI with GFR 76

For E. coli urinary tract infection with a GFR of 76, the recommended dosage of Bactrim DS (trimethoprim-sulfamethoxazole) is one double-strength tablet (160/800 mg) twice daily for 10-14 days. 1

Dosing Recommendations

• Bactrim DS (trimethoprim-sulfamethoxazole) 160/800 mg (one double-strength tablet) should be administered orally every 12 hours for 10-14 days for urinary tract infections 1
• No dosage adjustment is required for a patient with GFR of 76 ml/min, as dosage reduction is only necessary when creatinine clearance falls below 30 ml/min 1, 2
• For patients with impaired renal function (creatinine clearance 15-30 ml/min), the recommended dosage is half the usual regimen; for patients with creatinine clearance below 15 ml/min, Bactrim DS is not recommended 1

Evidence Supporting This Recommendation

• The FDA drug label specifically indicates that for urinary tract infections in adults, the standard dosage is one double-strength tablet (160/800 mg) every 12 hours for 10-14 days 1
• The International Clinical Practice Guidelines by the Infectious Diseases Society of America (IDSA) and European Society for Microbiology and Infectious Diseases recommend trimethoprim-sulfamethoxazole as an appropriate choice for therapy when the uropathogen is known or expected to be susceptible 3
• For uncomplicated UTIs, trimethoprim-sulfamethoxazole has demonstrated clinical cure rates of 90-100% and microbiological cure rates of 91-100% when the pathogen is susceptible 3

Important Considerations

• Urine culture and susceptibility testing should always be performed when treating UTIs to ensure the pathogen is susceptible to trimethoprim-sulfamethoxazole 3
• If susceptibility is unknown and treatment must be started empirically, consider local resistance patterns - if E. coli resistance to trimethoprim-sulfamethoxazole exceeds 20% in your region, consider alternative agents 3
• Trimethoprim-sulfamethoxazole can cause a transient elevation in serum creatinine that does not reflect actual kidney function impairment but rather competitive inhibition of tubular secretion of creatinine 4, 5

Monitoring

• Monitor for adverse effects, which may include gastrointestinal intolerance, skin eruptions, and rarely, more serious reactions 6, 5
• Be aware that approximately 11.2% of patients receiving ≥6 days of treatment may develop laboratory changes consistent with acute kidney injury, though this is usually reversible upon discontinuation 5
• For patients with comorbidities such as hypertension and diabetes mellitus, closer monitoring may be warranted as these conditions increase the risk of renal insufficiency during treatment 5

Alternative Options

• If the patient has contraindications to trimethoprim-sulfamethoxazole or if the E. coli isolate is resistant, fluoroquinolones (ciprofloxacin 500 mg twice daily for 7 days or levofloxacin 750 mg daily for 5 days) are alternative options 3
• For complicated UTIs or pyelonephritis, initial parenteral therapy may be required, especially if there are concerns about antimicrobial resistance 3

Remember that while the standard duration is 10-14 days for urinary tract infections, clinical response should guide the actual length of therapy, and treatment should be adjusted based on culture and susceptibility results when they become available 3.