Felycin Versus Traditional HCM Treatments in Cats
By Dr. Kevin Toman, DVM · Medically reviewed November 1, 2026 · 40+ years in clinical practice · 300+ cats with HCM treated
Short answer: Traditional HCM drugs treat the problems HCM causes, like blood clots and fluid in the lungs. Felycin-CA1 (a weekly sirolimus tablet) is the first drug aimed at the disease itself. They are not rivals. They do different jobs, and many cats may need both Felycin-CA1 and traditional drug therapy.
Two kinds of treatment
Think of HCM like a leaky roof.
- Traditional drugs are the buckets and mops. They deal with the water: clots, fluid and rhythm problems.
- Felycin goes after the roof. It targets the thickening that starts the trouble.
You often need both.
Side-by-side comparison
| Drug | What it targets | Which cats | Evidence |
|---|---|---|---|
| Felycin-CA1 (sirolimus) | Heart wall thickening (the disease itself) | HCM with no symptoms (Stages B1, B2) | Proven; Stopped wall thickening over 6 months in one trial. FDA conditionally approved. |
| Clopidogrel | Blood clots | Cats with a large left atrium (B2) or a past clot (C) | Proven to lower repeat clots in cats that already had one. |
| Furosemide | Fluid in or around the lungs | Cats in heart failure (C, D) | Proven-- Standard of care for heart failure. |
| Atenolol (beta-blocker) | Fast heart rate, outflow blockage | Selected cats with blockage or rhythm problems | Used by many cardiologists to extend life in cats without symptoms. |
| Pimobendan | Heart squeeze in some heart failure cases | Selected Stage C cats | Used in selected cases. |
Felycin-CA1 in brief
- A cat-specific, delayed-release form of sirolimus (rapamycin).
- Given once a week at a target dose of 0.3 mg/kg.
- FDA conditionally approved in March 2025 to manage heart wall thickening in cats with subclinical HCM.
- Not for cats with liver disease or diabetes.
Clopidogrel in brief
Clopidogrel makes platelets (tiny clotting cells) less sticky. That lowers the chance of a clot forming in a stretched left atrium.
In the FAT CAT study, cats that had already had a clot did better on clopidogrel than on aspirin. It is widely used in B2 cats with a large left atrium.
It does not thin the heart wall.
Furosemide in brief
Furosemide is a "water pill." It helps the body get rid of extra fluid in heart failure. For a cat struggling to breathe, it can be lifesaving.
It does not treat the heart wall thickening.
Atenolol in brief
Atenolol slows the heart. It may help cats with a blockage where blood leaves the heart, or with certain rhythm problems.
Studies have not shown that it helps cats without symptoms live longer. It is not needed for every cat with HCM.
From Dr. Kevin's 400+ cats with HCM:
It's a question I get all the time. Can Felycin replace other cardiac drugs your cat is currently on?
The answer, almost always, is NO. Your cat will be healthiest using Felycin to fight the wall thickening of HCM, and traditional drugs to fight the issues that HCM causes.
And supplements such as nattokinase or rutin will NOT replace anticoagulant drugs like clopidogrel or riveroxaban. Please don't do this.
Can Felycin replace my cat's other heart drugs?
No, not by itself. Each drug has its own job. A B2 cat with a large left atrium may need Felycin for the thickening and clopidogrel for clot risk.
Never stop a heart drug on your own. Stopping clopidogrel or furosemide suddenly can put your cat at serious risk.
Which treatment fits which stage?
| Stage | Main goals | Drugs often considered |
|---|---|---|
| A | Watch for changes | None. Regular screening. |
| B1 | Slow the thickening, monitor | Felycin may be considered |
| B2 | Slow the thickening, lower clot risk | Felycin, clopidogrel |
| C | Control fluid, prevent clots | Furosemide, clopidogrel, others as needed |
| D | Comfort and quality of life | Higher-level heart failure care |
Felycin's US label covers cats without symptoms. For cats already in heart failure (Stage C or D), evidence is limited. In Dr. Kevin's 400+ cases of HCM treated, however, a percentage of these cats DO RESPOND TO FELYCIN.
Monitoring still matters
No matter which drugs your cat takes, keep up with:
- Repeat heart ultrasounds
- Blood pressure checks
- Bloodwork (especially liver values on Felycin)
- Counting sleeping breaths at home
Is your cat a Felycin candidate? Take the 3-minute check → [DR. KEVIN: add link]
Outside the US?
We ship Felycin routinely to the US, UK, and Canada. You start by sending your vet's prescription, or by enrolling your cat in our Cat Longevity Protocol. You can purchase Felycin from us and get guaranteed delivery, although it sometimes takes a few days.
If you live in the EU, Taiwan, Hong Kong, or China you can purchase Felycin from us. You start by enrolling your cat in our Cat Longevity Protocol. You provide the shipping, and we cannot guarantee delivery but we can absolutely send it your way.
Frequently asked questions
Is Felycin better than atenolol?
They ARE NOT EQUAL, and do different jobs. Felycin targets the thickening. Atenolol is for certain blockage or rhythm problems.
Is Felycin better than clopidogrel?
They ARE NOT EQUAL, and are not swaps for each other. Clopidogrel lowers clot risk. Felycin targets heart wall thickening.
Can my cat take Felycin with other heart medicines?
Yes. Your vet must review every drug and supplement your cat takes. The problem is that your vet typically has only 1-2 cats at a time on Felycin, and are often too busy to check. That's where Dr. Kevin comes in.
Does Felycin mean my cat won't need ultrasounds?
No. Repeat ultrasounds show whether the treatment is working and whether the plan should change.
Your next step
Want a second opinion on your cat's medicine plan? Enroll in our Cat Longevity Protocol and get your free Consult with Dr. Kevin.
Or check out our free HCM University
References
- Luis Fuentes V, et al. ACVIM consensus statement on cardiomyopathies in cats. J Vet Intern Med. 2020;34(3):1062–1077.
- Kaplan JL, et al. RAPACAT trial. J Am Vet Med Assoc. 2023;261(11):1628–1637.
- Hogan DF, et al. FAT CAT study: clopidogrel vs. aspirin after ATE. J Vet Cardiol. 2015;17 Suppl 1:S306–S317. [VERIFY: citation details and add link]
- US FDA. Conditional approval of Felycin-CA1. March 2025.
This article is for education only. It does not replace an exam, diagnosis or treatment plan from your own veterinarian. Prices and regulations change; confirm locally.