Tiludronic acid can be detected in blood and urine samples from Thoroughbred racehorses over 3 years after last administration.
Authors: Riggs Chris M, Thompson Sarah L, So Yat-Ming, Wong Jenny K Y, Wan Terence S M, Robinson Paul, Stewart Brian D, Ho Emmie N M
Journal: Equine veterinary journal
Summary
# Tiludronic Acid Detection in Racing Thoroughbreds: A 3-Year Window for Prohibited Substance Testing Bisphosphonates like tiludronic acid (Tildren®) are restricted in most racing jurisdictions for horses under 3.5 years old due to concerns about masking performance-limiting bone disease, yet little was known about how long evidence of administration could be detected post-treatment. Researchers analysed blood and urine samples from 24 Thoroughbreds (21 still in active training) using ultra-high-performance liquid chromatography-high-resolution mass spectrometry, including samples collected up to 3 years after therapeutic dosing. Tiludronic acid was detectable in every horse tested; whilst blood concentrations were consistently very low at 2+ years post-administration (below 0.3 ng/mL), urine results were more variable, with occasional higher readings detected even at 3 years post-dosing (up to 3.7 ng/mL in one case). This substantially extends the regulatory detection window beyond the standard 40-day post-administration period, meaningfully improving racing authorities' ability to enforce age-related restrictions and detect potential rule violations in younger racehorses. The findings underscore the importance of sensitive testing protocols and highlight that a single negative result cannot rule out prior bisphosphonate use, particularly when sampling occurs within the first few years of a horse's racing career.
Read the full abstract on PubMed
Practical Takeaways
- •Tiludronic acid administration cannot be concealed by timing sampling beyond 40 days; residues persist for years in detectable quantities in blood and urine
- •Racing regulatory bodies can rely on blood and urine testing to identify bisphosphonate use in young horses long after treatment, even in horses actively racing
- •Practitioners should be aware that any therapeutic tiludronic acid administration creates a detectable residue signature that may affect racing eligibility for extended periods depending on jurisdiction rules
Key Findings
- •Tiludronic acid was detectable in blood and urine samples from all 24 horses tested, including 2 horses sampled 3 years after administration
- •Blood concentrations at 2+ years post-administration were consistently very low (<0.3 ng/mL)
- •Urine concentrations were less consistent, ranging from <0.3 ng/mL to 16 ng/mL at up to 3 years post-administration
- •A single therapeutic dose of tiludronic acid can be detected via blood or urine analysis for over 3 years after administration