From the Research
For a patient weighing 85 kg with a UTI requiring IV Bactrim (trimethoprim-sulfamethoxazole), the recommended dose is 8-10 mg/kg/day of the trimethoprim component, divided into 2-4 doses, as supported by the most recent and highest quality study 1.
Dosing Calculation
For this 85 kg patient, the dose calculates to approximately 680-850 mg of trimethoprim daily.
Administration
Since IV Bactrim is typically formulated as 80 mg trimethoprim and 400 mg sulfamethoxazole per 5 mL, an appropriate regimen would be:
- 8-10 mL (160-200 mg trimethoprim) every 6 hours
- or 12-15 mL (240-300 mg trimethoprim) every 8 hours.
Considerations for Severe UTIs
For severe UTIs, the higher end of the dosing range is preferred.
Treatment Duration
Treatment duration is typically 10-14 days for complicated UTIs, though this may be adjusted based on clinical response.
Monitoring and Hydration
Ensure adequate hydration during treatment and monitor renal function, as dose adjustment is necessary for patients with creatinine clearance below 30 mL/min, as noted in 2 and 1.
Rationale
This dosing provides adequate antimicrobial coverage against most common UTI pathogens while maintaining therapeutic drug levels in the urinary tract, aligning with the principles outlined in 3 for optimizing pharmacokinetic characteristics to minimize resistance and maximize clinical benefit.