I don't know if I have ever mentioned this, but I have osteopenia (precursor to osteoporosis). I take Actonel, a drug that increases bone density. Unlike most drugs I've taken or considered, I took Actonel without really knowing how it worked--as a rider and young horse owner I am just thankful that it does work.
Now there's a horsey-equivalent
And now, for horses with navicular, ringbone, hock, or other bone issues, there is an IV drug called Tildren. If you follow equine medicine, you've almost certainly heard of it. But if you haven't, here's a layman's description. Standard disclaimer: I'm no expert -- think of this info as something you overheard in the barn aisle. Read the authoritative resources if you want the more authoritative scoop.
Bones: Always under construction
Bone tissue is always under construction, it's normal for both humans and horses. When bones experience heavy loading (e.g., concussion, weight-bearing work), the tissue tries to rebuild itself and become stronger/denser. That's why my doctor recommended weight lifting to combat my bone problem. But excessive work produces an inflammatory response and excessive remodelling that ultimately weakens the bone. Here's some detail on how that happens.
Goofus and Gallant of the skeletal realm
Two types of bone cells play a part in bone remodeling: osteoclasts, "bone nibblers," tear down bone (see picture, above, from Tildren brochure). Osteoblasts, bone builders, create new bone. In normal bone, they work together to maintain bone health, but osteoblasts work more slowly than osteoclasts. When the remodelling process goes into overdrive, osteoclasts tear down bone faster than osteoblasts can rebuild it -- so more bone is lost than gained.
Tildren to the rescue
Tildren stops the osteoclasts from breaking down the bone -- kills the cells actually -- which gives the osteoblasts a chance to work. Over the course of months this increases bone density. Tildren works best on horses who have been unsound for six months or less, and the results vary. When it works, the difference is visible on x-rays and horses are noticeably more sound.
Late to the party
Tildren is not yet been approved by the FDA (as far as I can tell) but vets in the U.S. who go through special licensure are able to obtain it through the FDA and prescribe it. Judging from COTH posts, a lot of horse owners are getting treatment for their horse. Is it really as great as the hype suggests? In Veterinary News, one U.S. vet made an interesting comment that suggests how effective Tildren is...
"A while or so back we would receive mature performance horses with long careers imported from Europe with reasonable radiographs and no lameness issues when they arrived," explains Warsham. "Then, for no reason, after a while, they would develop any number of lameness issues. We started thinking that they (European owners, trainers and veterinarians) must have had something, probably Tildren, that they were using to help keep these 'older soldiers' sound."
Judging from that comment alone Tildren seems to be extending the useful life of many horses. That's really great news! But experts warn that it is an imperfectly understood treatment of degenerative processes (navicular, arthritis, etc.) that also are not well understood. Either the men of modern medicine are being too modest (which I doubt), or we just manage to stumble onto treatments. In any case, I'm sure glad these human drugs are being applied in equine medicine.
More in Part 2 of this series, Treating with Tildren (what to expect)...
Bone Quality from the National Osteoporosis Foundation (a good primer)
Information on Tildren from Georgevetgroup.co.uk
Navicular disease in horses from Equinehorsevet.com
Tildren discussion on COTH (featuring Reed Ayer, credentials at the bottom of the thread)
Should you consider Tildren for navicular? from Horse Journal (requires login, darn it)
French drug shows potential for navicular therapy Equus Magazine, Nov 2003
Navicular disease: New treatment from Equine Science Update
Navicular disease and spavin: New treatments from Equine vet/podiatrist (blog)
Tildren brochure (from Tildren manufacturers of course, but very nice illustrations)
Tildren: Denoix study shows Tildren helps with back pain from Fran Jurga's blog
Promising new navicular therapy from Equisearch.com
Treating Navicular Disease From inside the bone from The Horse magazine
Evaluating treatment choices for tendon, ligament injury and joint disease in the horse from Veterinary News
Tildren drug therapy, a forum posting by a DVM
Tildren, the Magical Product against Lameness?! from Eurodressage
Equine Bone Fragility Disorder reported in California from The Horse magazine
1 Horse and Hound online forum