By: Frank Angst

Veterinarian Jeff Blea, chairman of the racing committee of the American Association of Equine Practitioners, relayed a story from a couple years ago when he asked a room of about 200 equine vets if any of them had administered bisphosphonates?

Four or five raised their hands, but …

“Afterward, about 25 or 30 of them were asking me if there was a test for it,” Blea said of the medications used to treat osteoporosis in humans that have become popular with equine vets.

Blea told that story while participating on a panel discussing the appropriateness of bisphosphonate use in race horses, especially in young horses, during the animal welfare forum April 4 at the Association of Racing Commissioners International conference on equine welfare and racing integrity in Hot Springs, Ark.

Like in humans, bones in horses are in a constant state of breaking down and building back up. They can be reshaped based on need as bone cells increase to address added stresses. In humans, who are not able to regenerate bone or are limited in mobility, bisphosphonates prevent breakdown of current bone cells, thus maintaining bone density.

In Thoroughbreds, this regeneration process is necessary to develop healthy bones that can meet the demands of racing.

Blea and Sue Stover, a professor at the University of California-Davis school of veterinary medicine, noted there is limited information available on the efficacy and side effects of administering bisphosphonates to young horses—often before training or during initial training.

“The reality of it is that we don’t know enough about it,” Blea said. Despite that, he said it’s his understanding that use of bisphosphonates is rampant in Thoroughbred yearlings and at 2-year-old sales. He said he’s heard of its use in racing as well, but he’s not as confident about its use in that environment.

Breeder Carrie Brogden of Machmer Hall said the discussion was enlightening because she’s heard from veterinarians advocating the use of bisphosphonates to treat sesamoiditis and subchondral bone cysts in young horses. Brogden said her operation has resisted using the drugs, though many breeders are doing so.

Stover said there are veterinarians who believe in the use of bisphosphonates in young horses, but she has concerns about the lack of a scientific study.

Stover and Minnesota Racing Commission equine medical director Lynn Hovda said bisphosphonates are not able to target problem areas. They affect all of a horse’s bones.

“I think you have to recognize that when you’re treating with bisphosphonates, you’re treating the whole horse. I think you have to keep that in mind. There may be other ways to manage those conditions besides medication,” Hovda said. “These drugs go to bone in general, not just a cyst or a sore sesamoid.”

With that in mind, there are questions about the long-term effects on the bone regeneration process if bisphosphonates are administered at a young age. Looking at studies in humans, Stover said there are mixed results on this topic.

Stover said ailments for which bisphosphonates would be properly administered are not common in horses in training. She’s heard of them being administered—in an off-label use—to treat sore backs or sore hocks. Those pain-killing and anti-inflammatory effects are also a concern.

“Aside from, ‘What is it exactly doing to the bone?’ an additional concern in my mind is the pain-modulating effects of bisphosphonates,” Blea said. “There needs to be more science done to understand the effects in younger horses, as well as the effects of pain medication.”

Last year, the British Horseracing Authority outlawed the use of bisphosphonates in horses younger than 3.5 years old and restricted their use to products licensed for horses in the United Kingdom. They also required a diagnosis from a veterinary surgeon that supported its use as an appropriate treatment, and required that it be administered by a veterinary surgeon.

In trying to envision how the U.S. could regulate the use of bisphosphonates in young horses, ARCI president Ed Martin suggested working with the major Thoroughbred sale companies.

Blea said the issue has caught the attention of many in racing and breeding.

“Bisphosphonates are a nuclear button right now,” Blea said, “not only in the racing community but in the breeding community.”