Should We Be Using Bisphosphonates for Horse Soundness Maintenance?

Photo © Lauren Mauldin

BY JESS CLAWSON

As equestrians, we care a lot about our horses’ well-being and soundness. Chronic lameness in any competitive or pleasure riding horse can be devastating. We can spend an awful lot of money on supplements and medications, but how do we make decisions about what to feed or inject into our beloved equines? Sometimes it’s easy to skip the research and trust our trainer or vet, but our horses belong to us and it’s job to make the final educated call.

Tildren is the brand name of bisphosphonates that is often used in horses. It’s FDA approved for use in horses with navicular disease. Unfortunately, tendency is often to decide that if a drug is good for one thing, it’s good for lots of other things too. That leads to using drugs and supplements beyond their intended or approved purpose without studies to show us the harm they can do or if they even work at all.

Tildren works on the bone. As David Ramey, DVM, says, “Bone is an active tissue.  New bone is constantly being made and removed (that’s one reason that you can break your arm and it can heal).  In normal bone metabolism, the formation and removal of bone gone hand-in-hand. It’s because bone is an active tissue that bisphosphonate drugs can have an effect.”

Tildren essentially hinders the cells that remove bone in that continuous formation/removal cycle. This means it slows down bone reformation and bone loss, and because of the way the cycle works, slowing bone loss also means slowing bone formation.

Photo © Lauren Mauldin

It makes sense that this drug came to be used in people experiencing bone loss due to diseases like osteoporosis and why it is used in treating navicular disease. What does not make sense is the new habit of using it in horses because of some vague idea that it helps with “maintenance” of the bone.

Dr. Larry Bromlege, renowned equine orthopedic surgeon, told the Paulick Report that he wishes “we’d never seen these drugs” because of the side-effects shown in using the drug off-label. He sees people using bisphosphonates to treat soundness issues because they have a short term analgesic effect. For up to 30 days after administering the drug, the horse seems sounder, whether it is healthy or not.

Bromlege is concerned about the inhibition of the horse’s ability to heal an injury resulting from training: “Part of the horse’s natural coping mechanism is disabled,” and thus the healing rates of bone injuries are stunted on radiograph. “We can no longer rely on the repair process that we have come to expect as normal for the horse,” he said.

Ramey contends that some of the things Tildren is being used for are “just silly,” including the show circuit’s idea that it’s good for “maintenance.” That’s not how bone works. That’s not how any of the science works. Bone has to have the balance of removal and formation to be healthy. Using Tildren that way is, in fact, the opposite of a good maintenance plan.

Photo © Lauren Mauldin

Of course, any drug that has effects has side effects, and anything that doesn’t have side effects doesn’t have effects beyond placebo–that’s just how medical science works. Long-term use of bisphosphonate drugs do show some evidence of increased bone fragility as well as damage to equine joint cartilage. Studies have also shown side effects of colic and kidney failure in horses.

Remember: Tildren is approved to treat navicular disease in horses. Using it for any other purpose means you’re using it in a way that has not been approved via a process of clinical trials, so there is not only no documented evidence of efficacy, but there is also incomplete knowledge of the level of harm that is done. As Ramey says, “If you’re using it as some sort of ‘maintenance’ therapy, you’re going out on a limb which isn’t attached to a tree.”

If you are concerned about your horses having strong bones, assuming your horse does not have some kind of bone disease, the best thing you can do for your horse is a long, slow, careful conditioning plan. Bone is active tissue, but it also forms more slowly than other tissues like muscle. It’s important to understand how conditioning works in the equine athlete, not just in terms of muscles and their cardiovascular fitness, but also in terms of how bone develops, especially in young horses. Less lunging (and no lunging of babies), more long walks on rolling hills, which is a lot more fun for you and the horse anyway.

Moral of the story: Learn what drugs do before you give them to your horse. You don’t need to go to vet school to do this, I promise. Not only might it save your horse the short or long term unwanted side effects of a drug, it will save you money you could spend on what your horse really wants: cookies.