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Trimethoprim Urine Excretion and Its Potential for Treating Canine Urinary Tract Infections
Butch KuKanich1, Kate KuKanich1, Brooke Paisley1
1Kansas State University, College of Veterinary Medicine, Manhattan, Kansas, USA.
Journal of Veterinary Pharmacology and Therapeutics
|July 25, 2026
Summary
Antimicrobial resistant urinary tract infections (UTI) in dogs are increasing. This study found that a single oral dose of trimethoprim in dogs achieved urine concentrations potentially effective against Enterobacterales UTI, suggesting a viable treatment option.
Area of Science:
- Veterinary Medicine
- Pharmacology
- Infectious Diseases
Background:
- Antimicrobial resistance in canine urinary tract infections (UTI) presents a growing clinical challenge.
- Traditional treatments like sulfonamides can cause severe adverse effects in dogs.
- Trimethoprim, used alone in human UTIs, offers a potential alternative.
Purpose of the Study:
- To evaluate canine urine trimethoprim concentrations following a single oral dose.
- To determine if these concentrations could be effective against common UTI pathogens in dogs.
Main Methods:
- Nine healthy dogs received a single oral dose of trimethoprim (5 mg/kg).
- Urine samples were collected at multiple time points (pre-dose, 6, 8, 12, 24 hours).
- Trimethoprim concentrations were quantified using validated mass spectrometry.
Main Results:
- All measured urine trimethoprim concentrations exceeded the human breakpoint (8 mcg/mL) for Enterobacterales at 6, 8, 12, and 24 hours post-administration.
- Concentrations ranged from 17.2-413 mcg/mL across the time points.
- Significant variability in urine concentrations was observed.
Conclusions:
- Oral trimethoprim monotherapy may achieve effective urine concentrations for treating canine Enterobacterales UTI.
- Further studies are required to establish specific canine pharmacodynamic breakpoints and confirm clinical efficacy.
- Trimethoprim represents a promising therapeutic option for managing resistant canine UTIs.
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