Osphos and Tildren

These two drugs are doing more to revolutionize the treatment and management of equine bone and joint disease than any other. Up until recently the FDA has made it difficult to access Tildren as it could only be imported through a special process. Most of the early work with Tildren had been conducted in Europe. The good news is that now both medications are available in the US which will be of tremendous benefit to numerous horses. The treatment protocols have changed with time, but the enthusiasm for these medications has grown immensely.

These medications belong to a class of drugs called bisphosphonates. In human medicine the drugs have been used for such conditions as osteoporosis (condition seen with aging women), bone cancer and with periodontal disease. The principal activity is to inhibit bone resorption. Bones undergo constant turnover, with osteoblasts forming bone and osteoclasts resorbing it. In normal bone tissue, there is a balance between bone formation and bone resorption. But in diseased bone tissue, this balance is disrupted. Bisphosphonates inhibit bone resorption by encouraging osteoclasts to undergo cell death, leading to a decrease in the breakdown of bone. Beyond this they have played an important role in reducing bone-related pain in such conditions as bone cancer and metastatic bone disease.

Bisphosphonates preferentially âstickâ to calcium and bind to it. Because most of the bodyâs calcium is stored in bones, these drugs accumulate to a high concentration only in bones. Bisphosphonates are incorporated into the bone matrix and are gradually released over months to years.

There are several listed benefits to these medications and all are important in the management of the inflammatory process affecting bone:

  • inhibit bone resorption by blocking activity of osteoclasts

  • increase bone density

  • inhibit secretion of enzymes that degrade the cartilage on joint surfaces

There may be potential uses in a variety of equine lameness conditions; the most studied at present are: Navicular Syndrome, Hock Disease (Spavin) and Kissing Spine Syndrome. There are exciting clinical results being published on these diseases that are often notorious for being difficult to manage. These medications may give us a new avenue to manage diseases that are recognized by their effect of permitting the bone breakdown process to exceed the bone rebuilding process. If we can limit the bone loss during the inflammatory process and further degeneration that ensues then we should be able to positively affect the bone structure and reduce pain.

In the 7 years I have treated over 75 horses that have gone through lameness work-ups by me and/or had nuclear scans and/or MRI exams. The majority have had a lameness attributed to disease of the navicular region, some due to bone edema involving the feet or hocks and others due to kissing spine syndrome. At this point the results have been overwhelmingly positive in some very difficult cases.

Tildren is administered through a catheter over a 60 minute period. A second treatment is beneficial especially for those with more chronic or extensive conditions. An occasional horse is reported to have transient colic signs, fortunately this has not happened with any I have treated. Pre-medicating them with another drug plus administering the Tildren as a slow IV drip seems to be working well to avoid any problems.

The newer medication, Osphos will be used in identical situations as Tildren, but will be significantly easier and less costly to administer. It's given as intra-muscular injections and while there is still a possibility of colic-like symptoms they seem less likely to happen than with Tildren.

I anticipate using Oshos more as we continue to identify specific conditions that could benefit from its unique pharmacological attributes. Of course lameness will continue to be a multifactorial process, both in terms of making a firm diagnosis and coming up with a treatment plan, but with this drug I can approach some of these conditions with a bit more optimism for my clients.

For a number of our aging athletes it's not unusual for them to be living with conditions that, like us, affect them on a daily basis. We have a number of approaches to managing these things from intra-joint injections, systemic medications like Legend and Adequan, the use of anti-inflammatories and alternative therapies such as chiropractic adjustments, acupuncture and mesotherapy. By considering the role of bisphosphonates such as Osphos and Tildren, we may have yet another means to manage and "down regulate" the inflammation associated with bone and joint discomfort.

Above images from Dechra's website.