MONITORING FUROSEMIDE IN RACEHORSES PARTICIPATING IN AN EIPH PROGRAM

Analytical procedures were developed to monitor furosemide concentrati ons in post-race serum and urine samples obtained from horses particip ating in an exercise-induced pulmonary haemorrhage (EIPH) program. Hig h performance liquid chromatography with ultraviolet light detection p roved a reliable, sensitive method for measuring urinary furosemide co ncentrations up to 12 h after administration of either 150 or 250 mg o f the drug to race horses. However, this method was unreliable for det ermination of serum furosemide concentration. High performance liquid chromatography with fluorescence detection proved a reliable, sensitiv e method for measuring serum furosemide concentrations in horses admin istered 250 mg of the diuretic, permitting detection of approximately 5-10 ng/ml 6 h after treatment. This method was applied to field condi tions where furosemide was administered to horses (between 150 and 2 5 0 mg intravenously) 4 h prior to the race. Analytical results assisted in establishing a threshold concentration of 85 ng/ml for serum furos emide. It was found that serum furosemide concentrations are a valid m easure of compliance with furosemide administration in the EIPH progra m.