Study shows bisphosphonates detectable in hair for up to six months

A study examining the use of hair in detecting the administration of bisphosphonates in horses has determined that the method can consistently detect the substances up to six months after administration, the study’s authors said on Thursday, although the results also found some shortcomings in reliability.

The study, which arose out of a call for research by the Grayson-Jockey Club Research Foundation in 2019 into the impact and detection of bisphosphonates, demonstrates the efficacy of using hair testing in determining whether bisphosphonates were recently administered to a horse, the authors said. The study’s principal investigator was Heather K. Knych, of the University of California-Davis, a leading equine researcher.

The study administered a dose of bisphosphonates to seven horses. In four of the seven horses, tests applied to the hair could detect elements of the dose six months after administration. However, the study’s authors noted “significant inter-individual variability in detection times” of 63 to 180 days and “several intermediate times where the drug could not be detected but was subsequently detected in later timepoints.”

Although bisphosphonates are approved by the FDA to administer to horses that are 4 years old or older to treat navicular disease, they are banned for use in all Thoroughbred racehorses under rules that went into effect on May 22. Under those rules, any horse testing positive for bisphosphonates is banned for life.

Racing commissions began banning the non-prescribed use of bisphosphonates in 2019 after the administration of the drugs to young horses led some equine pathologists to link them to bone injuries. Bisphosphonates can inhibit bone growth and remodeling in young horses.

Testing for the drugs in urine and blood had led to inconsistent results, and in some cases, blood tests were finding traces of the drugs years after they were administered.

“Being able to detect bisphosphonates long-term in hair benefits the athletes and increases the integrity of the sport,” said Knych.

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