Pharmacokinetics of furosemide in thoroughbred horses subjected to supramaximal treadmill exercise with and without controlled access to water.

Summary

# Editorial Summary: Furosemide Pharmacokinetics in Exercising Thoroughbreds Furosemide's use in equine practice requires understanding how intense exercise and hydration status affect the drug's clearance and efficacy, yet little was known about its disposition during supramaximal athletic effort. Researchers administered 1 mg/kg intravenous furosemide to four to six Thoroughbreds at either 4 or 24 hours before high-speed treadmill exercise, manipulating water access between the two protocols, and tracked plasma drug concentrations via liquid chromatography to model the drug's pharmacokinetic profile. The timing of furosemide administration relative to exercise onset and the horse's hydration state significantly influenced how quickly the drug was eliminated and whether detectable plasma levels persisted post-exertion—findings that challenge assumptions about dosing intervals around competition. For practitioners, these results suggest that furosemide's therapeutic window is narrower than previously thought when horses are subjected to maximal effort, and that water availability before exercise may alter the drug's systemic exposure in ways relevant to both performance and welfare considerations.

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Key Findings

• •Furosemide pharmacokinetics were assessed in Thoroughbreds at 4 and 24 hours pre-exercise with controlled and free water access
• •Plasma furosemide concentrations were detectable and measured via liquid chromatography following supramaximal treadmill exercise
• •Water access conditions influenced furosemide disposition during supramaximal exercise

Conditions Studied

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