New Treatments for Bone Pain In Horses

New Treatments For Bone Pain In Horses

by Charlene Cook DVM

You’ve probably seen the commercials with Sally Field (the older generation including myself will remember her from the TV show “The Flying Nun”). Sally is touting the benefits of a drug called Boniva. Boniva is a bisphosphonate that is prescribed to treat osteoporosis in women.


Other bisphosphonates used in people include Actonel, Fosamax, Reclast, Aredia, Skelid, Zometa and Didronel. Bisphosphonates are also used to treat bone changes in diseases such as Lupus, Cystic Fibrosis, Osteogenesis Imperfecta, and Multiple Myeloma. Bisphosphonates are also used in some types of breast, lung and prostate cancer where metastatic disease tends to occur in bones.

So why would I be telling you about bisphosphonates? Well they are also used in horses to treat certain types of diseases that tend to cause lameness. So what are bisphosphonates and why would we use them. To understand how bisphosphonates work we need to review bone metabolism. Bones are constantly changing. That might surprise you, we think of our bones as being “finished” once we have stopped growing. The fact is our bones are constantly remodeling based upon the stresses placed upon them. Weight bearing exercise tends to increase bone strength whereas inactivity tend to cause bone loss.
Let’s say you decide to take up jogging. Your bones will send signals to the Osteoblasts (bone makers) in your body to add more calcium to your leg bones and spine. On the other hand let’s say you fell and broke your hip. You have several months of rest to allow the fracture to heal. During this time your body would send Osteoclasts (bone removers)to remove extra calcium from the same bones.

Normal bone activity
Your bones are made of living tissue, and are constantly changing. In healthy bones, specialised bone cells constantly break down and replace bone tissue. These specialised bone cells are
•    Osteoclasts – which break down old bone
•    Osteoblasts – which build new bone
This process is called bone remodeling and is very well controlled. There is a fine balance between the rates of bone breakdown and growth, which keeps bones strong and healthy.

Bone Remodeling and Bisphosphonates
The normal bone remodeling pathway requires that bone resorption (digestion of bone) and new bone formation take place at the same site and in a coordinated fashion. Usually, the amount of bone formed during bone remodeling equals the amount destroyed. Any disruption in this balance results in disease to the bone, including bone loss.

The main effect of a bisphosphonate is to decrease bone resorption. Bisphosphonates act to inhibit bone resorption by decreasing the number and the activity of osteoclasts.
During bone stress or disease, bone metabolism is accelerated and osteoclasts are stimulated to begin the remodeling cycle.

Osteoblasts follow behind the bone-eating cells, but at a much slower pace. Accelerated bone resorption may exceed the bone rebuilding process during these times of chronic bone disease or stress, including navicular syndrome.

Drugs such as bisphosphonates regulate bone metabolism through inhibition of bone
resorption and bring the balance of osteoclast and osteoblast activity back to normal by reducing the activity of the osteoclasts.


 So how does this apply to your horse?
In some types of disease such as Navicular Syndrome bone loss is occurring at a greater rate than bone formation. The bone develops cystic changes or holes where the blood vessels enter the bone. This weakens the bone and causes pain for the horse. Stopping the bone loss helps to stop the progression of the disease.

Other uses for bisphosphonates include degenerative arthritis of the distal tarsal joints or "Bone Spavin" and degenerative arthritis in the spine known as "Kissing Spines". More recently we are using this class of drugs with greater frequency in any case where degenerative changes are occurring in the bone including advanced laminitis or "Founder", palmar metacarpal bone disease of the fetlock, enesiophtye in the long bones and any case with bone edema seen on MRI.
There are two bisphosphonates licensed for use in horses. Tildren and OsPhos. Tildren (Tiludronate disodium) has been available for many years but was only available in the United Kingdom. Importing the drug was a slow and expensive process. In 2014 the USDA finally approved Tildren for use in the United States. Tildren is given by intravenous infusion. An intravenous catheter is placed and the drug is given by slow IV infusion. There is a slight risk of colic with Tildren and Banamine is given as a premedication to reduce this risk.

The best time to evaluate the treatment is1 month after treatment, but signs of improvement are often seen 15 to 21 days after treatment. For horses that respond favorably the treatment can be repeated every 6-12 months.

OspHos (Clodronate disodium)was released a few months ago. OsPhos is given by intramuscular injection.
The ability to give OsPhos by intramuscular injection eliminates the need for an intravenous catheter and provides a more economical alternative for many horse owners.

Some horses may show some pain after injection that generally stops within 30 minutes. Osphos can be repeated every 3-6 months if needed.

Some horses are not candidiate for bisphosphonates. Young horses such as weanling and yearlings are still growing and use is not recommended. Bisphosphonates are removed from the body by the kidney. Horses with kidney disease are at risk for complications and treatment is not recommended.
Tildren and OsPhos can both be used with other joint therapies such as hyaluronic acid injections, joint supplements and therapeutic injections such as Adequan, Legend and Pentosan may be continued.
For more information visit

For more information on Navicular Syndrome click here

For more information on Bone Spavin click here

For more information on OsPhos click here.

I hope you found this information helpful. Please feel free to give me a call if you think your horse may benefit from the use of Tildren or OsPhos.
As always you can reach us anytime at 478-825-1981
Thank you for reading,