Hair analysis for long-term detection of bisphosphonates

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Hair analysis has shown promise as a method for detecting bisphosphonate use, even up to six months after its administration. 

 

Bisphosphonates, commonly used in human medicine to treat bone disorders, have been approved for use in adult horses. However, there is a growing interest in off-label use of bisphosphonates in young racehorses to manage and prevent certain musculoskeletal conditions.

The safety and effectiveness of bisphosphonates specifically in young racehorses have not been extensively studied or established. These drugs work by inhibiting bone resorption, the natural process of breaking down old bone tissue to make way for new bone formation. In young animals, maintaining the delicate balance between bone formation and resorption is crucial for proper bone growth and remodelling.

 

Modifying this balance through bisphosphonate use may have unforeseen consequences on the development and integrity of the skeletal system. It is important to carefully consider the potential risks and benefits before using bisphosphonates in young racehorses.

 

Due to the concerns surrounding bisphosphonate use in horseracing, strict regulations are in place. However, enforcing these regulations requires an effective method of detecting unauthorized use.

 

Hair analysis has emerged as a reliable approach for detecting drug administration in horses, as it can detect drugs for an extended period after their administration. Recognizing this potential, a research team consisting of scientists from the University of California, Davis, and the University of Kentucky College of Agriculture, MH Gluck Equine Research Center, conducted a study to develop an assay and evaluate the viability of hair as a matrix for long-term detection of clodronate, a bisphosphonate, in horses. This research initiative was initiated in response to a specific request for bisphosphonate-related research by the Grayson-Jockey Club Research Foundation in 2019.

 

“Over the past few years, bisphosphonate use has become a concern with regard to the welfare of Thoroughbred racehorses,” said Jamie Haydon, president of Grayson. “We are very thankful for the generous support by Vinnie and Teresa Viola’s St. Elias Stables and their ability to recognize the importance of this research in promoting equine safety and welfare.”

“Bisphosphonates are labelled for horses 4 years and older to manage navicular symptoms,” said Dr. Johnny Smith, A. Gary Lavin Research Chair of Grayson. “Unfortunately, people were using them in young horses, which is detrimental because bisphosphonates inhibit bone resorption, can stay in a horse’s system for years, and can have long-term effects on bone.”

In this study, the researchers administered a single intramuscular dose of clodronate (1.8 mg/kg) to seven horses. They collected hair samples before the administration and at various time points up to 6 months afterward.

 

The presence of the drug was initially detected on day 7 in four out of the seven horses. In the remaining three horses, clodronate was detected on days 14, 28, and 35, respectively.

The drug was still detectable in four out of the seven horses even 6 months after administration.

 

Previously published studies, including one conducted by the same group and funded under the same special call, demonstrated that in some cases bisphosphonates can be detected in blood and urine for extended periods of time, but detection using these matrices can be unpredictable and less consistent.

“Our study from 2020 showed that clodronate and tiludronate reside in the bone for extended periods,” said the study’s principal investigator, Dr. Heather K. Knych, who is with the K.L. Maddy Equine Analytical Chemistry Lab’s Pharmacology section and the Department of Molecular Biosciences, at the School of Veterinary Medicine, University of California, Davis. “This can lead to lasting pharmacologic effects and increase the risks of injury to racehorses. Being able to detect bisphosphonates long term in hair benefits the athletes and increases the integrity of the sport.”

 

For more details, see:

 

Long-term monitoring of clodronate in equine hair using liquid chromatography-tandem mass spectrometry. 

Heather K. Knych, D.S. McKemie, S. Yim, S.D. Stanley, R.M. Arthur. 

Journal of Chromatography B, Volume 1226, 2023, 123789, 

 https://doi.org/10.1016/j.jchromb.2023.123789