Are there any large animal vets on this forum?
If so, any thoughts on sirolimus for horses?
My situation: I’m 73, a female, who started riding 6 years ago when I retired from full-time work. 4 years ago, at 69, I bought my first horse: an incredibly well trained registered quarterhorse mare, A year ago, buoyed by the energy and wellbeing I felt from 10 months of rapamycin, I bought my first horse property.
My beautiful horse is now 20, and I dread losing her and/or not being able to ride her. I see the signs of aging, although she is still quite lovely to ride.
We are giving our aging dogs rapamycin with good results, and the question comes up: what about the horse?
Any thoughts? resources? bad idea? idea whose time has not yet
come? good idea?
thanks in advance.
She’s about 1000 lbs, I figure about 30mg would be her dose.
As Matt Kaeberlein says… it has worked in all subjects across differences… yeast, worms, flies, mice, dogs… why not horses. Probably takes a bigger dose.
I think its a good idea. I fed rapamycin to my chickens and it seemed to keep them laying eggs at peak production for about 4 years, by which time my kids were no longer interested in eggs for breakfast. So I think it would work for horses too.
1,000 lbs = 450kg
In the dog aging study right now they are doing .15mg/kg, so that would equate to 67mg.
My only question would be getting the tablets down the throat of the horse without the horse chewing the tablets up. I don’t know horse chewing dynamics, but there has to be something they like to eat that they don’t chew too much - perhaps push a bunch of tablets into an apple, assuming that they would mostly swallow the apple whole.
If you try it, let us now how it goes. And try to track some measurable results, and metrics that might demonstrate if its working or not. Perhaps number and length of rides you do in a week, if you are a regular rider.
@RapAdmin@Agetron Thank you for your support (and also doing the math).
One way to mark progress would be with some of the horse apps that track your time at the trot, time at the canter, time at the walk. A horse that trots for 20 minutes straight is considered in good condition–I could do a pre-rapa time, and then periodic intervals during and after rapa.
I’ll keep you all posted
Glad to hear it helped your chickens!
@Radiata There’s a joke in the horse world–“what do horses eat?”
“Cash, they eat cash.”
An interesting question, but I doubt anyone knows. Its not like horses get organ transplants, or cancer therapy… I suspect they have not even developed the blood assay for horses (I’m not a phlebotomist so I have no idea if you could use a human test for a horse, but I suspect not)
Are there such things as horse Fitbits / Activity trackers? That would be interesting to see see how much more active overall (not just short measures) a horse on rapamycin is vs. not on rapamycin. Perhaps modify a human Fitbit to put on a leg of the horse (just an extra large band); track for a few weeks prior to starting rapamycin to get a baseline of daily activity, then retest / monitor after rapamycin.
Or perhaps just attach a human Fitbit to the harness and another to the saddle, so you get full data when the horse is ridden or not.
So much I don’t know about the digestive system of a horse. I know the hay goes to a huge colon. They’re not ruminant, so don’t think they chew the cud. I’ve not had one, but I have goats and when I thought about using Rapa on them I decided it probably would not work. I think the best way to know you get it in them would be to inject subQ.
Did I see, back when Mac was always talking about it, someplace that sells injectable Rapa? Or did he talk about making his own?
If you figure out how to buy an injectable form, let me know. I’m thinking of using it on an older doe to see what happens.
We’re in the middle of harvest right now and I don’t have a lot of time to read.
I don’t know the importance and activity of the CYP3A4 enzyme in horses… I would research it to figure out if the impact is of the same magnitude.
While its unlikely any vets have given rapamycin to horses in the past (I’m not aware of any organ transplants ever being done on horses), there is possibly literature on the impact of citrus fruits and the CYP3A4 enzyme in horses at it relates to medication dosing impacts.
If the impact in horses is the same as humans, that would lower the weekly dose to something like 23 mg of rapamycin per week, which is pretty easy from a dosing and cost perspective.
Would be nice to have a Vet chime in. I wonder what the overlap of testing centers like labcorp are for blood samples from non-human species. Seems like the standard human blood test for sirolimus should work on horse blood.
If it were me I’d work out a way to test levels and determine half life. Then try to match the levels of other studies where consensus on dosing has been reached. Going at it blind seems too expensive and you would never know if you are making any difference.
I have horses and have been wondering about this too! I know that when my horse was on arthritis meds labeled for dogs, she took 1/4 the large dog dose (per my vet’s instructions). My friend with a large dog looked up his Rapamycin dose and it was twice her (the dogs owner) dose. So on that basis, maybe a horse needs half a human dose?
I have no idea if dosage for arthritis meds (obviously there are various ones and I don’t remember which one my horse was on) and Rapamycin work the same way. But I do think that for some meds, at least, horses require a much smaller dosage than their size would imply.
@LeahM
Thank you for that input, about dosages for horses sometimes being smaller–I will try to pick my vet’ brain regarding equine absorption–I know their guts are ridiculously long, causing them all kinds of GI problems that sheep goats, and cows don’t have.
I have yet to find a vet, either for my dogs or my horses, who seems interested n rapamycin–I think they are just really busy keeping up with everything.
I’m a veterinarian, but strictly small animal. I think the molasses is an excellent idea for getting the tablets down without being chewed.
As for dosages and the horse dose of arthritis medication being smaller than the large dog dose, it depends on which arthritis medication you are using. It’s not across the board lower doses for all medication. Pharmacodynamics and side effects vary widely across species, as would half life, depending on the drug.
I think giving a low dose, checking blood levels and calculating your own half life for your horse is a good approach.
@Paul_Moss
Thank you for those suggestions: i will print out rapa info for my horse vet on the 16th when he comes to take a look at my horse and try to pick his brain about equine absorption, metabolism, half-life, etc. And get some bloodwork–looking into what labs.
The human labs (ie. Labcorp) should be able to check the sirolimus levels on horse blood without any problem. There are iPhone apps that would allow you to easily calculate the half life from two blood draws, if you know the exact time of the draws. I use this one: Half-Life Calculator on the App Store. It’s for nuclear decay half life, but it’ll do the calculation very accurately.
You probably need to check what type of vial you need to draw the blood in for Sirolimus blood levels.
Later, when you figure the dosage to use, remember that adequately low trough levels are important in avoiding side effects.
I did a rushed search on the internet using “equine sirolimus” and found this: Effect of sirolimus on insulin dynamics in horses - PubMed . There are probably other articles too, but I had to get to an appointment, sorry.
They got a half life of 3552 (3248-4767) minutes. (~2.47 days) in their paper. The half life will vary between individuals, as shown in those times. So determining your horses’ individual half life is best.
I can look more later.
@Paul_Moss
This is a fantastic article! (and the full text is free)
It not only gives the dose used (0.06mg per kg)
but it used sirolimus both IV and orally–with good discussion about the low trough concentration (1.5ng/ml vs human kidney transplant 12-30ng/ml trough). And more! yahoo!
my vet is coming on the 16th–we can discuss this as she gets tested for Cushing’s and insulin dysregulation. Many, many thanks!
