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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132 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 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.”
    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.

  11. Ademan says:

    “Other studies have kept the capsules intact, and it still didn’t work.”

    Do you mind linking/citing some of these? I’m a lay person trying to soberly evaluate azodyl for my CKD cat (Vet has already said “can’t hurt to try”). Of course I *want* to believe it works since that gives me hope, but I’m aware of that bias and I want all the information I can get. I’ve only seen the two studies you mentioned here: the “original” one sponsored by vetoquinol, and the subject of this article.

    Based on my lay person understanding, probiotics containing live organisms require the intact capsule in order to survive into the intestines and do their thing, so I’m not really surprised breaking open the capsule reduced or eliminated its efficacy, I don’t think you can generalize from that.

  12. skeptvet says:

    The two studies I have reported in dogs (here and here) both used the intact capsules. There is also some evidence that colonization with live organisms isn’t always necessary for probiotics to have beneficial effects, so we cannot simply assume that opening the capsule invalidates the results of a study.

    In any case, there is not reason to think the product should help and no research evidence showing it does, so using it is really just rolling the dice. The company should be the one expected to prove their claims, since they are making money selling the product, and when there is some negative evidence and no positive evidence, it is hard to make the case that there is still much reason to try it.

  13. Diana says:

    Hi all for anyone having problems administering the pill. I buy the greenies pill capsules they’re too small to cover the whole pill so originally my cat was spitting it out but because the treats are So soft I would basically mold it around the entire treat and he would basically swallow it maybe a chew here and there. One time It came up w a fur ball and the entire pill was still fully intact within the treat. I’m hoping that means it’s getting into his system whole. Wanted to pass this trick along in hopes it helps! They’re the only soft pliable treats I’ve found but I’m sure anything super soft works! At first he didn’t love the flavor but I started using one treat he loved then the pill in the second treat followed by 2 more regular treats. Good luck!

  14. Cynthia Hampton says:

    To those of you who give your cat Azodyl: How in the world do you get your cat to swallow a capsule? I can give my cat is little round pill for her thyroid, followed with a little bit of NutriCal, and he just licks and swallows. But this capsule is totally different and he just spits it out.

  15. Sims says:

    My cat is 17 and is in stage 4 renal failure when dignosed 2.5 years ago.he started out on the kd diet. Didnt like it. Fluids twice a week. His food of choice is purnia pro plan savory wet and dry. He was put on azdoyl 7 months ago and we have seen a big difference. He just had bloodwork his kidneys are good and have been for a long while. Changes we made are fluids 4 times a week now. Same additives baytril and b12. Famotidine was added a few months ago. I do sprinkle it in a tiny bit of creamy pate food and mix it up …to be sure he gets it all. Then i feed him as much food as he likes. He gets it every 12 hours this way.

  16. Io says:

    There are special seringes tha you can use in order to be a le to feed The pill to your cat. Just look IT up on Google. And yes, after months of experimenting, it is easier to feed IT through one side of her mouth. She Will open her mouth muuch easier like that.

  17. Bella says:

    My cat has CKF. I do not remember her BUN/creatnine but my vet has this info. She has been on Atenolol/Benazepril to control blood pressure/beta blocker for 10 years now. In the past 6 months she has gotten worse, her coat is not as soft, she is not liking food, although she always runs to eat but actually does not. She has stopped drinking a lot of water she used to drink. So I continue to administer medication above, she is getting 100-150 ml subcutaneous fluids daily. Today I started on Azodyl. I actually inserted a pill in her mouth and made her swallow it. She had a little bit of food in 2 hrs after I administered Azodyl. The supplement is kept in a fridge. I have also administered Epakitin (via syringe) with food. She ate a little but nothing exciting. I will report if I see any differences. She is 17 years old.

  18. Gayle says:

    Hello..have you had any updates on the condition?

  19. Linda Steed says:

    I have a 16 year old cat who had BUN 111 creatinine was 9.2 in the hospital twice in five days.. that was eight months ago I found Astros oil online he has been taking it ever since and his bun is now down to 49 his creatinine is 2.6 he is eating regular food he seems to feel very good acting like he’s normal Astros oil is a highly processed fish oil which combats oxidative stress the other two supplements nitrogen creatinine scrub and phosphate free Renal Care protein he has been on all three since the beginning of February he’s doing excellent in fact the doctor said his blood work was so stable he called him in remission. Just Google Astros oil and look at all of the testimonials I am thrilled with it

  20. skeptvet says:

    Glad your cat is doing well, but this says nothing about the product you are promoting. I routinely treat cats with kidney failure in the hospital, and when they go home their creatinine is lower and stays that way due to the treatment they receive in the hospital. Here’s some more info on why anecdotes aren’t actually good evidence for medical treatments.

    Why Anecdotes Can’t be Trusted

  21. nx says:

    Have there been any studies on Azodyl given as instructed, rather than sprinkled on food?

  22. skeptvet says:

    Yes, one in dogs and one in cats, and neither found any benefit.

  23. amiknyc says:

    I just started my cat on Azodyl and she takes the full capsule with a tiny dollop of food with no issues. I’m eager to see if there is any improvement after a month or two. She has already been on a steady path to recovery having switched to Darwin’s Raw Kidney Support food along with blood pressure medication. She has been taking fish oil daily her entire life as well. Recently, she has been meowing a lot before drinking water or after going to the bathroom. Two veterinary visits found nothing wrong and they summed it up to the fact that she is 17, we recently moved and introduced another cat into the household, and she is just more vocal at this stage in her life. No idea if the Azodyl will do anything but because she takes it exactly as directed, I am curious to see what will happen if anything.

  24. skeptvet says:

    I hope your cat does well, but of course this kind of try-it-and-see approach is pretty unreliable at telling us which therapies wrk and which don’t. Some explanations for why are below;

    Lots of reasons why anecdotes like this aren’t reliable and don’t actually tell us if therapies work or not:

    Why Anecdotes Can’t be Trusted


  25. Len Go says:

    I tried Azodyl until I finished the bottle. I diligently give the pill to my cat every single day. Her renal blood work showed no improvement. Azodyl, AminAvast (even made it worst- from 2.3, became 2.9- creatinine), Kidney pet well being- all No good! Such a waste of money and time. I wonder why a lot of owner were saying it worked to their fur babies. The one that made my cat’s ckd stable – Porus One (I ordered from my brother in UK), recently available in US, Rehmania 6 from Etsy, and SUC- HEEL (I ordered from Germany. Her recent blood test showed stable ckd, been a year ago, exactly and her (creatinine at 2.7) and her vet told me, to continue what I have been doing, because my cat is in great shape, getting a lot of muscle mass(not losing muscle mass, and IDEXX SDMA went down from 20 to 16. (NOPE TO prescription foods- no idea why they are even prescription, as there are no special ingredients there, except low quality meat and loaded with carbs. She is eating high quality rare/raw chicken mixed with supplements. Hope this information helps.

  26. skeptvet says:

    Unfortunately, such “I tried X,Y, and Z and here’s what happened” anecdotes aren’t a reliable guide to what works or doesn’t work. You will find hundreds of these, and for every one that claims Z works and X and Y don’t, another hundred will claim the opposite. What is needed is scientific research.

    In the case of diets, there is strong research that these diets extend life and benefit cats with CKD, so it’s unfortunate that you have been misled to think of them as poor quality. They are prescription because the balance of macronutrients and micronutrients that is beneficial to cats with CKD could be harmful to cats with normal kidney function. Nutritional management of kidney disease is useful and a lot more complex than you suggest.

    Here’s a bit more detail on why anecdotes aren’t very helpful:

    Why Anecdotes Can’t be Trusted


  27. Luz says:

    Could you write the name? The links are deleted by the system.

  28. Noyb says:

    Your research used the product incorrectly. Instructions were not followed or they purposely were not.
    Azodyl has worked for 2 of my cats when nothing else would and they would have been long gone.
    It was the only change in their routine. That’s enough evidence for me.

  29. skeptvet says:

    Sadly, many people believe that such personal experiences prove which treatments work and don’t. It’s the main reason ineffective and unsafe therapies persist. It is actually very clear that such anecdotes are unreliable and mislead us all the time, but people find them compelling anyway. If you are open to the possibility that things aren’t always as they seem, here is more info (and some humor) on this subject.

    Why Anecdotes Can’t be Trusted


  30. Christianna Billman says:

    Actually, the mercury usually DID help with the immediate ailment and back then the people didn’t live long enough for the bad long term side effects to show up. It was a great treatment for syphilis, which would kill people a lot faster than the mercury would. Not that I’m a fan of Azodyl yet, mind you. My dog seems to have lost all of his appetite on it and is going downhill quickly. But I think that would have happened either way since he’s in stage IV. Who knows?

  31. Lisa Haydon says:

    My cats bun was 60. She has been on azodyl for about a month. My only problem is I am not sure it’s always on an empty stomach. So I wondered if it still works. She always gets the whole capsule. lol it’s a fight I have to burrito her but she gets it twice a day.

  32. Thank you a very useful article and all of your comments to the various people.
    After a year of SQ fluids and Purina NF wet food (mixed with the Wellness that she really likes), our vet said we could try azodyl, crushed in wet food, for our 18-year old, stage 3, kitty. After reading all this, I’ve come to the conclusion “why bother?” She is pretty stable, and seems happy, and we just want to enjoy her and whatever time we have left together.

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