Azodyl for Kidney Failure in Cats: An Update on the Evidence

In a recent article about pet supplements for the Science-Based Medicine Blog, I reviewed the dietary supplement Azodyl, marketed for kidney failure in dogs and cats. At the time, the evidence I was able to find was extremely limited, poorly controlled, and subject to a high risk of bias due to association of the research with the company marketing the products. My conclusion was that the theory behind the product was weakly plausible and the evidence insufficient to justify a firm conclusion about efficacy.

An abstract is being presented at the upcoming American College of Veterinary Internal Medicine Forum which reports the results of a controlled study on the use of this product in 10 cats with  chronic kidney disease.

M. Rishniw; S. Wynn
Azodyl Fails to Reduce Azotemia in Cats with Chronic Kidney Disease (CKD) When Sprinkled Onto Food 

The study examined whether there was any difference between commonly measured blood markers of kidney disease, blood urea nitrogen (BUN) and creatinine, in cats given Azodyl and cats given a placebo. The Azodyl was sprinkled on the food since this is commonly how the product is used (making cats take capsules is often difficult). The study was randomized, double blinded, and placebo controlled. The criteria for confirming a positive effect were quite generous, however no difference was found between cats given Azodyl and cats given the palcebo.

The authors concluded:

Based on these results, Azodyl, applied by sprinkling onto food fails to reduce [BUN and creatinin] in cats with [chronic kidney disease]. Whether intact capsule administration reduces reduces azotemia in cats with [chronic kidney disease] remains unknown.

Though generally well-designed, this study was small, and of course single studies are almost never sufficient to provide the final word on a particular therapy. The issue of potential bias for or against a hypothesis is always hard to evaluate objectively, but I am unaware of any direct funding or other involvement of the company in this study. I do know that one of the authors, Dr. Susan Wynn, is a prominent researcher and advocate in the area of herbal and some other alternative therapies, so she certainly would not be expected to have a bias against the product. And negative findings in clinical research are inherently more reliable than positive findings because our studies and our psychology are designed to confirm our beliefs rather than refute them. So while the case is by no means closed, the balance of the very limited evidence is currently against any significant clinical value for this product.

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110 Responses to Azodyl for Kidney Failure in Cats: An Update on the Evidence

  1. JethroT says:

    Hello…I have an 18 year old cat, Molly, who was recently diagnosed with Kidney “failure” which seemed an odd diagnosis to me as I would think kidney failure would mean death. Anyhow….she was prescribed with Azodyl and Methimalzole for this condition. Like most others in here have suggested it is almost impossible giving her the capsule. I have done many studies and watched you tube videos of Vets making pilling your cat easy, it is certainly not that with Molly. She takes the Methimalzole whole in a pill pocket, no problem, but simply refuses the capsule. I have tried removing the contents of the capsule and sprinkling it on food, or adding it to a little milk and putting it in a syringe. Now I see from comments in this blog that unless it is given as a capsule, Azodyl is worthless. I am due for a follow up visit to the vet this week.
    Does anyone know of a liquid alternative?

  2. skeptvet says:

    Methimazole is for thyroid disease, not kidney disease, and it is important to follow up with your vet to make sure your cat responds appropriately and the dose is adjusted to his or her needs. Too much can make the kidney problem worse, so this monitoring is important.

    The term “kidney failure” is pretty imprecise and old-fashioned. We now grade the severity of chronic kidney disease according to a standard scale which is then used to guide management, so again make sure you are clear with your vet about what stage your cat has and if all the right factors are being monitored and managed (bloodwork values, blood pressure, protein in the urine, etc).

    There is no evidence to suggest any kind of probiotic is going to make a difference, so I would not waste time and energy and money looking for an alternative to Azodyl, which almost certainly doesn’t work anyway.

  3. DrDEq says:

    I am an equine veterinarian who owns a CRF cat, now a year out from his diagnosis. He is 14. In that year, I have updated my knowledge of feline renal disease, as well as living it day to day. I have found a few things that might be helpful. First, for allergic cats. Royal Canin makes a renal support, hydrolyzed protein kibble. My cat is very allergic and lived on Hill’s Z/D for much of his life. He would eat, but could not tolerate, any of Hill’s renal foods. I turned to the Royal Canin hydrolyzed protein first, but then discovered by trial and error that he can eat any/all of the Royal Canin renal support foods, kibble or canned. So, before you turn to nutritionist-formulated diets (that’s a lot of work), it might be worth giving RC a try. Second, constipation. My guy has periodic issues with this and will back off eating and generally feel less well. I have started adding acacia fiber powder to his food. (Renew Life makes an organic one that is very nice.) It is soluble and tasteless (I became acquainted with it while doing a smoothie diet myself. I can personally attest to the lack of taste.) He prefers his kibble mixed with a little water and microwaved (gently, please) to form a sort of “gravy train” result. I add the acacia fiber to this mixture and it dissolves and he laps it up. Added benefit of getting a little extra water in him as he isn’t in love with wet food. Giving him this mixture (about 1/8 tsp per serving or as tolerated) 2-3X daily has pretty much resolved the constipation problem. If stools get a little too soft, cut back on the amount slightly. Third, subQ fluids. I learned from a blogger to try thin-wall needles. They have a larger inner diameter for the same outer diameter. I am currently using 21 gauge and am thinking of going to 22g. The fluids take less than 5 minutes to run in (100-125ml) and he is much happier than with the larger gauge needles. Fourth – probiotics. I have not tried any of these products on my cat. I once gave him one dose of Dasuquin for his joints and it took me a week to get him straightened out after vomiting and all manner of GI upset. So, tread lightly with some of these dietary additives. On the other hand, the more I learn about the GI microbiome, the less I feel that I know, so if your cat feels better when you give the probiotic AND the cost doesn’t prevent giving him something that we KNOW works AND you don’t have to compromise your relationship to administer it, I would not say no. But that’s a lot of qualifiers. Fifth – there is a paper that I have found most helpful. It may be way technical for many, but if you are into trying to read good information read through the ISFM Consensus Guidelines on the Diagnosis and Management of Feline Chronic Kidney Disease. Tried and true evaluation and recommendation of options for all the nuances of CRF by a panel of experts in the field. So, to all of you CRF cat owners/lovers out there, I am one of you, but we must also keep in mind that this is not about us. This is about the well-being of the cats. CRF is a terminal disease, but then so is life, so try to see the glass as half full and just enjoy your beloved kitties while you can. Think quality over quantity. It’s not about how long you can keep them alive. It’s about how well they can be while they are alive. And they don’t fret about it like we do. They don’t know they have renal failure. They just wake up every morning (noon, or night) and proceed with their day, so try not to mar that precious innocence more than necessary in the name of not having to say good-bye for another day/week/month. And thanks to all of you for your devotion to these incredible little guys. Our world is a better place because of them. And you.

  4. Angela Dillinger says:

    Hello. I’ve had 3 cats on Azodyl. My Vet assured me it was fine sprinkled on food however the directions state do not open or crush capsules. I contacted the manufacturer. I was told the capsule needs to be intact to be effective in the small intestine however if I must open the capsule it can be mixed with an oil and given. My cats would not swallow the capsule so I mix it in a capsule of fish oil. One cat will lick it up however the other I have to draw into a syring and give it that way. The manufacturer did say it was only 80 percent effective this way. I have a 22 year old cat who has been stable on this drug for 3 years. Buy the lowest dose of fish oil possible and contact the manufacturer for any other questions.

  5. Claire Briddon says:

    Very helpful, despite conflicting experiences…still very helpful for the vet advice and the personal experiences of how to administer the meds and sub-q and what to ask your vet about. I live overseas now and vets are not always up-to-date..so thank you!

  6. Jean says:

    That’s incredible. Wonderful.

  7. Christine says:

    You’re not supposed to open the capsule. It’s not that difficult to get it in a cat.
    After one dose Azodyl got my stage 4 cat eating again. Her numbers were better and she was on Azodyl and a phosphorus binder only. Her vet gave her a week and she passed 5.5 months later….not due to kidney disease. Her numbers were better. The vet was impressed.
    Explain that.

  8. skeptvet says:

    Other studies have kept the capsules intact, and it still didn’t work. And renal values fluctuate as part of the natural course of disease all the time, so the fact that they went down after giving the product isn’t evidence it worked. If it were, we could just stop doing scientific research and rely on our subjective experiences, but that has failed us dramatically throughout history. You have simply rediscovered the Post Hoc Ergo Propter Hoc Fallacy:

    A logical fallacy that states “Since event Y followed event X, event Y must have been caused by event X.”
    Examples-
    A tenant moves into an apartment and the building’s furnace goes faulty. The manager blames the tenant’s arrival for the malfunction. One event merely followed the other, in the absence of causality.

    The Brazilian footballer Pelé is said to have blamed a dip in his playing performance on having given a fan a specific playing shirt; after getting the shirt back his performance recovered. The loss of the shirt was given as the reason for his dip, and its return the cause of his recovery. However, it was later discovered the shirt returned was not the original shirt.

    Here is some more information on why anecdotes can’t be trusted:

    Why Anecdotes Can’t Be Trusted

  9. Pete H. says:

    My 12 year old spayed Oriental was just put on Azodyl after her blood work was done…She has been on an 1/8th of a tablet of Ursodiol, once a day, for a few years now….She has always been a healthy cat…No eating problems, Royal Canin Urinary SO, both canned and dry and Hills TD’s for her teeth….She is small, 9lbs, but her weight is always stable….She has never had a problem urinating or with bowl movements….I have read the comments about Azodyl and am wondering why my Vet put her on Azodyl and if there is any contra indications with the Ursodiol ?..Thank you for any comments..

  10. skeptvet says:

    Your vet likely has fallen for the “well, it can’t hurt and it might help” argument, which unfortunately is untrue. It probably doesn’t help, and we don’t know if it can hurt or not since there is very little research. There is no obvious reason it would be a problem with ursodiol, but it’s likely just a waste of your effort and money to give it.

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