Rapamycin dosage for dogs and cats: what the trials used, and why we won't give you a number

People search for this constantly, and the internet obliges with dosing charts. We are not going to add one, and the reason matters more than the number.

Why a website cannot give you a dose

Rapamycin dosing is not a lookup table. It depends on your animal's weight, the species (a cat is not a small dog and does not metabolise drugs like one), the formulation (a delayed-release preparation behaves differently from a plain capsule), the schedule (several times weekly versus once weekly), and everything else your animal is taking or dealing with.

It is also a prescription drug with real interactions. The gap between a low intermittent longevity protocol and the daily immunosuppressive dosing used in transplant medicine is the entire distinction that makes this drug interesting — and getting it wrong in either direction is how you cause harm rather than avoid it.

A number on a page cannot know any of that. A veterinarian looking at your animal can.

What the published trials actually used

That said, you are entitled to know what the literature says — that is what this library is for. This is scientific context, not a protocol:

• Dogs. The 2017 randomized trial used low-dose rapamycin given several times a week for ten weeks in middle-aged companion dogs, and found it well tolerated with a signal on cardiac measures. The much larger TRIAD trial uses low-dose intermittent dosing over a far longer period and has not reported.
• Cats. RAPACAT used a once-weekly delayed-release formulation in cats with subclinical heart disease, and measured tolerability rather than benefit. Once-weekly is a meaningfully different schedule from the canine protocols — one more reason feline dosing cannot be extrapolated from dogs.
• Mice. The lifespan results everyone quotes come from dietary dosing in mice, at exposures that do not translate directly to a dog or a cat by body weight.

Notice what is missing from that list: a validated long-term dose for extending life in either species. It does not exist yet, because the trial that would establish it has not reported.

The principle behind low, intermittent dosing

Understanding this makes the vet conversation better.

At high, continuous doses — transplant medicine — mTOR inhibition suppresses immunity. At low, intermittent doses, human trials showed the opposite: improved vaccine response and fewer infections in older adults. The intermittent schedule is thought to allow mTOR to recover between doses, capturing the maintenance benefits without sustained suppression.

That is why every serious pet protocol is low-dose and spaced out — and why "more must be better" is exactly backwards here.

What to ask your vet instead of Googling a number

• What dose and schedule would you use, and which published protocol is it based on?
• What formulation — compounded capsule, tablet, delayed-release — and why that one?
• What bloodwork do we do before starting, and how often after?
• Which of my animal's current medications interact with this?
• What would make you stop treatment?

The bottom line

If a site hands you a dosing chart for a prescription drug without knowing your animal, that tells you something about the site. The dose is a clinical decision, and the honest thing we can do is give you the trial context and send you to someone who can make it.

Our quiz will tell you which studies apply to your animal and what should stop the conversation entirely; the how to get it page explains the routes.

Not veterinary advice, and deliberately not a dosing guide. Rapamycin is prescription-only — dosing belongs to a veterinarian who has examined your animal.

References

1. Urfer S.R. et al. A randomized controlled trial to establish effects of short-term rapamycin treatment in 24 middle-aged companion dogs. GeroScience, 2017. Find on PubMed
2. Fries R.C. et al. Delayed-release rapamycin in cats with subclinical hypertrophic cardiomyopathy (RAPACAT). Find on PubMed
3. Mannick J.B. et al. mTOR inhibition improves immune function in the elderly. Science Translational Medicine, 2014. Find on PubMed