Poster Presentation 24th International Conference of Racing Analysts and Veterinarians 2026

Urinary excretion of tiludronic acid following an intravenous infusion of Tildren® to horses. (130258)

Glenys K Noble 1 , Colin J Scrivener 1 , Josh Klingberg 2 , Paul Berghouse 2 , Lance Brooker 2 , John Keledjian 2 , Adam Cawley 3 , Jaymie Loy 1
  1. School of Agricultural, Environmental and Veterinary Sciences, Charles Sturt University, Wagga Wagga, NSW, Australia
  2. Australian Racing Forensic Laboratory,, Sydney, NSW, Australia
  3. Racing Analytical Services Ltd, Flemington, Victoria, Australia

There has been limited research into the urinary excretion of tiludronic acid (TA) administered to horses. Work carried out in the 2000s could not measure urinary TA due to poor sensitivity of the assay.  As most race day drug testing in Australia is carried out by collecting urine samples from horses, there is a dearth of knowledge to satisfactorily detect the abuse of this drug. Laboratory analytical methodology has improved greatly over the years since this first study, so the present study addressed this deficit.

Eight horses (four mares, four geldings; mean age: 9 ± 2 years; mean body weight: 591 ± 61 kg) had urine samples collected 6 days prior to, and on the morning of drug administration. Horses were dosed at 1.0 mg/kg disodium tildronate infused IV at 20 mL/min over 30 minutes. Urine samples were collected 2 h after infusion completion, then at increasing intervals to 12 h, and daily from 24 h to 168 h. Weekly samples were collected to 28 days. Urine was analysed for TA using LCMS. Descriptive statistics were calculated using SigmaPlot V13.0.

Urinary TA was detectable from 2 h post-administration at high concentrations, particularly in mares. All mares had maximum urinary TA concentrations (Cmax) above 10,000 ng/mL with only one gelding returning a Cmax above 10,000 ng/mL. Mean (± SD) urinary Cmax for mares was 14,723 ± 3928 ng/mL at 3 ± 1.15 h compared with geldings at 5199 ± 5024 ng/mL at 2.5 ± 1 h. Urinary excretion varied between mares and geldings with significantly different TA urine concentrations over the sampling period. Urinary TA concentrations between the sexes did not become similar until 3 weeks after TA administration. Urinary TA concentrations remained above the limit of quantification (1 ng/mL) at the end of the 28-day sampling period.