Bactrim Dosage for Uncomplicated Urinary Tract Infection
The recommended dosage of Bactrim for uncomplicated urinary tract infection in adults is one double-strength tablet (160 mg trimethoprim/800 mg sulfamethoxazole) twice daily for 3 days. 1, 2
Dosing Recommendations by Patient Population
Adult Women with Uncomplicated UTI
- One double-strength tablet (160 mg trimethoprim/800 mg sulfamethoxazole) twice daily for 3 days 1, 2
- This 3-day regimen is preferred over longer courses due to similar efficacy with fewer side effects 1
- Clinical cure rates range from 90-100% when the pathogen is susceptible 2
Adult Men with UTI
- One double-strength tablet (160 mg trimethoprim/800 mg sulfamethoxazole) twice daily for 7 days 2
- Men typically require longer treatment duration than women 2
Special Populations
- For patients with impaired renal function (creatinine clearance 15-30 mL/min): half the usual regimen 3
- Not recommended for patients with creatinine clearance below 15 mL/min 3
- FDA labeling suggests 10-14 days for urinary tract infections, but current clinical guidelines support shorter courses for uncomplicated UTIs 3, 1
Efficacy and Considerations
- Early clinical cure rates with the 3-day regimen range from 86-100% 1
- Bacterial cure rates range from 85-100% with the 3-day regimen 1
- Treatment efficacy significantly decreases when the infecting organism is resistant to trimethoprim-sulfamethoxazole, with clinical cure rates dropping to 41-54% 2
Important Caveats and Limitations
- Trimethoprim-sulfamethoxazole should only be used as empiric therapy when local E. coli resistance is <20% 1, 2
- If local resistance exceeds 20%, alternative first-line agents should be considered 1
- Common side effects include rash, urticaria, nausea, vomiting, and hematologic abnormalities 2
- Side effects are significantly fewer with 3-day regimens (1.4-31%) compared to 10-day regimens (15-38%) 1
- Contraindicated in the last trimester of pregnancy 2
- Contraindicated in pediatric patients less than 2 months of age 3
Alternative Regimens When Trimethoprim-Sulfamethoxazole Cannot Be Used
- Nitrofurantoin monohydrate/macrocrystals (100 mg twice daily for 5-7 days) 1, 2, 4
- Fosfomycin trometamol (3 g single dose) 1, 2, 4
- Pivmecillinam (400 mg three times daily for 3-5 days), where available 1
- Fluoroquinolones are effective but should be reserved for more invasive infections 4