Rapamycin For Cats With HCM
Like Yours.
Rapamycin for Cats with HCM
What We Think We Know.
Rapamycin for HCM in Cats– The Background.
Rapamycin has shown proven benefit in treating cardiac disease, long before the Trivium study on HCM came out.
The Kaeberlein study out of UW showed that rapamycin improved left ventricular function in dogs, without any evidence of side effects. This is important because HCM in cats is also primarily a left ventricular disease.
Understanding that cats are not mice, last time I looked, here’s a study that showed rapamycin improved cardiac function in mice. Here’s the more interesting part: the cardiac benefits lasted even after the rapamycin was stopped.
Rapamycin has also been shown to improve cardiac function even in pressure-overloaded or ischemic states, both of which are known to exist in feline HCM.
The bottom line? Rapamycin appears to be a very safe drug with significant cardiac benefits in multiple species studied to date.
Rapamycin for HCM in Cats– The Trivium Study
Here’s the title of the Trivium rapamycin study: “Delayed-release rapamycin halts progression of left ventricular hypertrophy in subclinical feline HCM…” . Sounds promising, for sure.
But there are some things we should recognize about the study structure and results, such as…
- This was a small study of only 42 cats
- MOST IMPORTANTLY, the study deliberately excluded cats with…
- high blood pressure
- any symptom of congestive heart failure
- left ventricular outflow tract obstruction
- pimobendan therapy
- Lasix therapy
SADLY, THIS EXCLUDED POPULATION INCLUDES THE MAJORITY OF MY CAT HCM PATIENTS.
The study results showed that…
- Not all cats responded
- Positive results were most apparent after 6 MONTHS of therapy
- Cats with high BNP scores generally had a higher response to rapamycin therapy. (BNP is a common blood test which gauges the severity of cardiac stress)
Listen, I’m not raining on the Trivium parade, because THERE ARE NO OTHER DRUGS THAT HAVE SHOWN ANY ABILITY TO SLOW/STOP HCM PROGRESSION. But we need to recognize that there are some questions about how this will translate to HCM patients in the real world.
An Update on Our Results, as of 8/12/24. Six cats rechecked with echo exams after 3 mo on rapamycin, FIVE IMPROVED.
Hello Dr. Toman –
Rapamycin for Cats with HCM — The Medication
OK, let’s talk about rapamycin itself.
The rapamycin dosage recommended in the Trivium study is 0.3 mg/kg 1x weekly.
The Trivium study clearly states that they used a “delayed release” version of rapamycin. Unfortunately, they provide no formulation details and their proprietary tablet is not due for US release until 2026.
We know that rapamycin powder is degraded to a variable extent by acid levels typical of the human stomach. Cat stomachs are less acidic than humans’ are, but this is still a logical concern. This is the rationale for a “delayed release” formula — to get it through the stomach before the stomach acidity could, in theory, denature the rapamycin.
In practice, pharmacists use the phrase “delayed release” (DR) and “acid-resistant” (AR) interchangeably.
HERE ARE THE TWO “DELAYED RELEASE” FORMULATIONS OF RAPAMYCIN AVAILABLE FROM US RIGHT NOW.
- Generic Rapamune tablets used in human medicine, which are coated to achieve delayed release. THESE ARE THOUGHT TO BE IDENTICAL TO THE TRIVIUM TABLETS… but we don’t know for sure because of Trivium’s secrecy.
- An oil-based oral suspension, which can be flavored to the tastes of your cat. This formulation is very similar to the Rapamune oil suspension used in human medicine. The oil base is thought to protect the rapamycin from degradation in the stomach.
Which is superior? We don’t know, and likely won’t for some time. The ONLY way to know would be to start your cat on one, test their blood for rapamycin levels, then do the same thing on the other med. Rapamycin blood testing is NOT commercially available, so…
Good news with Logan’s echo! The thickening completely resolved! Let it be noted that Logan’s condition is probably secondary to the mitral valve dysplasia, but for it to happen this fast I am sure the rapamycin helped! Next echo will be in 6 months instead of 3… Hoping for this outcome to stick. Thank you so much!
(Note that, medicine being medicine, I cannot guarantee any outcome. So far we are 2/3 for improvement in HCM kitties on rapamycin. I will update this as we get more rechecks. — Dr. Kevin)
Purchase Rapamycin For Your Cat Now.
Help Your Cat Live Their Longest and Best Life.
About Me
Hey, there. Dr. Kevin here. I am a veterinarian who has been in clinical practice treating cats like yours for over 30 years. I live on the Central Coast of California, and have a passion for helping pets live longer. I am particularly interested in longevity drugs like rapamycin, dental care, and cancer therapy.
“Rapamycin is the only drug consistently shown to increase mammalian longevity…”
Z.D. Sharp, ScienceDirect.com, 2023
How To Get Rapamycin for Your Cat
1.
Rapamycin is a Prescription Drug
So your vet can write you a prescription.