This one drug has done more to revolutionize equine bone and joint disease in the past 10 years than any other. Unfortunately the FDA has made it difficult to access the drug as it can only be imported through a special process. Most of the early work with Tildren has been conducted in Europe. The treatment protocol has changed with time, but the enthusiasm for this medication has grown immensely.
As of 2014 the FDA has approved Tildren, but it is still not available for purchase in the U.S. as of August 1, 2014.
The drug belongs to a class of drugs called bisphosphonates. In human medicine the drug has been used for such conditions as osteoporosis (condition seen with aging women) 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.
Bisphosphonates preferentially “stick” to calcium and bind to it. Because most of the body’s 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 this medication and all are important in the management of the inflammatory process affecting bone:
inhibits bone resorption by blocking activity of osteoclasts
increases bone density
inhibits 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. This drug 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 3 years I have treated over 60 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.
The medication 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.
I anticipate using Tildren more as we 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.