Your Guide to Equine Health Care

Study Investigates How Long Bisphosphonates Stay in Horse Bones

Studies in other species show bisphosphonates’ elimination half-lives in bone are prolonged and can range from months to years, leading researchers to investigate their residence times in horses’ bones.

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Study Investigates How Long Bisphosphonates Stay in Horse Bones’
This study investigating bisphosphonate residence time in bones took bone samples of horses treated and not treated with bisphosphonates. | Photo: Courtesy Dr. Heather Knych
The use of bisphosphonates to manage bone disorders such as navicular syndrome, especially in race and performance horses, has become a recent (and controversial) topic of discussion in the equine veterinary community. Until now, no studies have been published describing the drug’s disposition in horse bones—an important consideration when assessing its side effects.

A team from the University of California, Davis, (UC Davis) and the University of Kentucky recently took the first step toward describing bisphosphonates’ residence time in horses’ bones. Heather K. Knych, DVM, PhD, Dipl. ACVCP, professor of Clinical Veterinary Pharmacology at UC Davis’ K.L. Maddy Equine Analytical Pharmacology Lab, presented their findings at the 2020 American Association of Equine Practitioners’ convention, held virtually.

How Do Bisphosphonates Work?

Knych first described what we do know about bisphosphonates and their mechanism of action. Under normal circumstances, the processes of bone formation and bone resorption are in balance. However, she explained, in some circumstances, such as aging, this balance can become disrupted, and resorption can overwhelm formation. The result is weakening of the bone.

Doctors use bisphosphonates to increase bone density and treat disorders of bone resorption (e.g., osteoporosis, Paget’s disease) in humans. In horses, these drugs (tiludronate, clodronate) are labeled to treat the clinical signs associated with navicular disease; however, veterinarians also administer them off-label for other bone

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Written by:

Alexandra Beckstett, Managing Editor of The Horse and a native of Houston, Texas, is a lifelong horse owner who has shown successfully on the national hunter/jumper circuit and dabbled in hunter breeding. After graduating from Duke University, she joined Blood-Horse Publications as Assistant Editor of its book division, Eclipse Press, before joining The Horse.

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