Researchers are working to further understand the effects of clodronate disodium, a bisphosphonate drug commonly used to manage equine bone pain and remodeling, on equine bone microarchitecture and bone mineral density (BMD) in juvenile horses. Veterinarians often administer clodronate in these populations, despite this being an extra-label use (approved for use in treating clinical signs of navicular syndrome in horses over 4 years of age). Brittany Paris, PhD, a visiting scientist at Texas A&M University, in College Station, presented her and colleagues’ work as a poster at the 2025 Equine Science Society Symposium, held June 3-6, in Fort Collins, Colorado.

Bisphosphonates inhibit bone resorption and were originally intended for horses with navicular bone lesions. Initially, these medications emerged to treat human patients with bone fragility disorders, such as osteoporosis. However, equine practitioners saw promise in using the drugs to treat podotrochlosis, a disease with no cure. In more recent years, veterinarians have observed off-label benefits when using bisphosphonates to treat a variety of musculoskeletal conditions. 

Studying the Effects of Clodronate Disodium in Yearlings

To investigate, the researchers studied 32 yearling Quarter Horses over a 168-day period. They divided the horses into groups based on sex and initial bone optical density and randomly assigned them to one of four treatment groups: no clodronate (control), a single-dose group, a two-dose group, or a four-dose group (1.8 milligram/kilogram body weight per dose). They housed the horses individually, exercised them five days per week on an automatic walker, and fed them a diet based on coastal Bermuda grass hay and commercial concentrate.

On Days 84 and 168, the researchers performed bone biopsies of the tuber coxae (hip bone, chosen because it is relatively easy to sample). Using microcomputed tomography (microCT), they analyzed samples for trabecular bone volume fraction (BV/TV), trabecular number (TbN), thickness (TbTh), separation (TbSp), and bone mineral density, which are parameters that help researchers evaluate bone strength and quality.

The team found no overall treatment effects on BMD or most bone microarchitecture parameters in the tuber coxae. They noted that BV/TV and TbTh tended to be higher in horses treated with one dose than in the control and four-dose groups. However, they noted these trends were driven by one horse and not likely to be physiologically significant.

Findings and Future Clodronate Research

These findings suggest that clodronate, even at multiple doses, does not significantly influence bone structure or density of the tuber coxae, a non-weight-bearing bone, in young horses under the conditions tested. Paris and her research team cautioned that further studies are needed to understand the long-term implications of clodronate administration, especially in actively growing performance horses.

“While some trends emerged, the lack of significant findings supports the conclusion that the clodronate administered in the current study had no effect on BMD or trabecular structure in the tuber coxae region,” the authors wrote.

Take-Home Message

Clodronate disodium had no significant effect on BMD or bone microarchitecture of the tuber coxae in young Quarter Horses under these study conditions. The researchers noted that more investigation is needed to make a thorough recommendation to practitioners and horse owners.