adventures with the vet · senior horse

Next Steps (Literally): Investigating OsPhos & Other Biophosphonate Drugs

Bad news first: Tristan is still lame.

From there, it’s actually mostly good news.

He was first off last Monday/Tuesday. He got one gram of bute am + pm through Friday afternoon, and then on Monday I put him on the longe line.

He was definitely not comfortable but a) he worked out of most of it and b) it was much better.

I asked the barn manager to watch him with me, and her observations matched my own: he was acting almost like he had a stone bruise. That RF was short and sort of stabby, like he didn’t want it to rest on the ground for long.

He was much, much more willing to move forward than he was at this point last week, offering up a canter to the right several times when he flat-out refused last week.

So what’s next?

First step: one month of Previcox, an anti-inflammatory that will be much better on his stomach than bute would. That will help ease overall osteoarthritis symptoms and anything more specific going on in that RF. I’ll keep checking in to see how he goes.

My hunch, based what he presented yesterday, taking into account his history and the way he looked? I think he’s showing some soreness in his foot from the ongoing RF problems, because that foot is (apparently) always going to be more sensitive and weaker to any kind of problem. It’s always going to be thrushy, always going to trend toward abscesses, and always going to show sole bruises immediately. I think it’s some kind of sole bruise.

However, I also think he’s got some ongoing arthritis issues in both his hocks and that coffin/fetlock. He is on monthly Pentosan injections, and that has helped with his overall fluidity in terms of the cartilage, ligaments, and tendons, but I think we also need to add something to help with inflammation.

Again, if he were younger and in full work, we’d start joint injections. He’s not and he’s not. I said this to the barn manager last night, and she raised a new possibility.

OsPhos is a new drug specifically marketed for the treatment of navicular. It basically helps joints and bones that are remodeling due to arthritis or abnormality. It has a really promising research outlook, and works in similar ways to Tildren, a drug that’s been on the market for a bit longer.

For my purposes, the benefits are thusly: it is a system-wide joint support that is not quite as powerful as an intra-articular joint injection would be but at the same time tackles more joints at one time. It is delivered IM, and costs between $200-$300 a dose. (As opposed to $1,000 a dose for Tildren, and $500/joint for injections). Perhaps most importantly, our local best lameness vet is very familiar with it and has used it on several of the schoolhorses in the barn to excellent effect.

That said: it has drawbacks. Some of them are not so great. Because it’s such a new drug, there are some serious concerns about longterm consequences.

The most legitimate concern seems to me to be the question of how, exactly, biophosphonate drugs like OsPhos (and Tildren) remodel bone. They work by basically killing the things that remodel bone, preventing bad changes from happening – but also good changes from happening. Bone remodels throughout its entire life. Stopping that from happening prevents bony changes, but it also prevents the kind of bone density growth that’s important in strengthening. Do they create truly good, new, strong bone, or do they just make x-rays look better?

These are drugs that have been available for humans for some time now, and on the 10 year outlook there are reports of necrotic bone (particularly in the skull and jaw) and dramatically lower bone density. There are also reports of spontaneous fracture.There’s lots on the COTH forums; here’s one good thread.

On the one hand: that is scary as shit.

On the other hand: Tristan is in light dressage work and he is 20. He is not jumping or otherwise putting sport horse stress on his bones. Would helping him be more comfortable and keeping him in light work to keep him healthy be worth the tradeoff?

On the other other hand, at least some of his lameness issues in that RF are due to bone remodeling, so the biophosphonates would help in that way. But they’re also due to a lack of bone in that area, ie the carved-out portion of his coffin bone from the infection. So they might help one problem and worsen another.

I also don’t see any good outlook on how many times a horse has to be dosed before the problems crop up – or before they are sound. “It depends” is always the answer.

There’s also the possibility, mentioned by a few people, of doing a regional perfusion of the problematic limb with Tildren. That would localize the treatment to the problematic RF, but it would also do nothing for his hocks and any other overall osteoarthritis he’s dealing with.

Anyway.

Lots to think about.

Has anyone out there used Tildren or similar drugs?

2 thoughts on “Next Steps (Literally): Investigating OsPhos & Other Biophosphonate Drugs

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