From the Guidelines
Bactrim (sulfamethoxazole-trimethoprim) for uncomplicated urinary tract infections is typically dosed at one double-strength tablet (800mg sulfamethoxazole/160mg trimethoprim) taken by mouth twice daily for 3 days in women or 7-14 days in men, as recommended by the most recent guidelines 1. The dosing regimen is based on the type of antibiotic and the complexity of the infection. For uncomplicated cystitis, the recommended treatment duration is 3 days with trimethoprim-sulfamethoxazole (TMP-SMX) 1.
- The American College of Physicians recommends short-course antibiotics with either nitrofurantoin for 5 days, trimethoprim–sulfamethoxazole (TMP–SMZ) for 3 days, or fosfomycin as a single dose for women with uncomplicated bacterial cystitis 1.
- The Infectious Diseases Society of America (IDSA) and the European Society for Microbiology and Infectious Diseases (ESCMID) also recommend treatment durations depending on the type of antibiotic, including 5 days of nitrofurantoin, 3 days of TMP–SMX, or a single dose of fosfomycin 1. It is essential to note that patients should take the medication with a full glass of water and maintain adequate hydration throughout treatment to prevent crystal formation in the urine. Bactrim works by inhibiting two consecutive steps in bacterial folate synthesis, making it effective against many common UTI pathogens, including E. coli.
- Common side effects include rash, nausea, and gastrointestinal disturbances 1.
- Patients with sulfa allergies, severe liver or kidney disease, or who are pregnant near term should not take Bactrim 1. The full course should be completed even if symptoms improve before finishing the prescription.
- The IDSA/ESCMID guideline focuses only on female patients and recommends either an oral fluoroquinolone for 7 days or TMP–SMX for 14 days for treatment of patients with pyelonephritis not requiring hospitalization 1.
From the FDA Drug Label
The usual adult dosage in the treatment of urinary tract infections is 4 teaspoonfuls (20 mL) of sulfamethoxazole and trimethoprim oral suspension every 12 hours for 10 to 14 days. The recommended dose for children with urinary tract infections... is 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, given in two divided doses every 12 hours for 10 days.
The recommended dosing for Trimethoprim-Sulfamethoxazole (Bactrim) for the treatment of a Urinary Tract Infection (UTI) is:
- Adults: 4 teaspoonfuls (20 mL) every 12 hours for 10 to 14 days
- Children: 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, given in two divided doses every 12 hours for 10 days 2
From the Research
Recommended Dosing for Trimethoprim-Sulfamethoxazole (Bactrim)
- The recommended dosing for Trimethoprim-Sulfamethoxazole (Bactrim) for the treatment of a Urinary Tract Infection (UTI) is as follows:
- It is essential to note that the choice of antibiotic and duration of treatment should be guided by urine culture and susceptibility results, especially in cases of recurrent infection, treatment failure, or atypical presentation 3, 4, 5, 6
- The effectiveness of trimethoprim/sulfamethoxazole may be reduced in areas with high resistance rates, and alternative antibiotics such as fosfomycin, nitrofurantoin, or fluoroquinolones may be recommended 4, 5, 6
Considerations for Antibiotic Resistance
- Antibiotic resistance rates should be considered when selecting an antibiotic for UTI treatment, and local resistance patterns should be taken into account 4, 5, 6
- Trimethoprim/sulfamethoxazole is no longer recommended as a first-line agent in areas with high resistance rates (>20%) 5
- Fluoroquinolones may be recommended as an alternative, but their use should be reserved for cases where other options are not effective due to concerns about resistance and "collateral damage" 5