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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Azodyl for Kidney Failure in Dogs–New Study Finds No Benefit

I have recently summarized the limited evidence concerning the use of Azodyl, a popular probiotic product, for treatment of kidney disease in cats, including a recent study presented as an abstract at the American College of Veterinary Internal Medicine Forum. Another study of this product has also been presented at the same conference.

David J. Polzin, DVM, PhD, DACVIM . Probiotic Therapy of Chronic Kidney Disease

This was a considerably more comprehensive research project, though still with some limitations, as is always true. 32 dogs with moderate kidney failure were randomly assigned to treatment with Azodyl or a placebo. They were otherwise treated identically according to a standardized algorithm for managing kidney disease. They were evaluated in terms of comprehensive bloodwork, body condition, and owner perception of quality of life and 7 time points from 1 month to 1 year after the start of the study. No significant difference in any measure was found between the groups at any time point.

The Azodyl was given as an intact capsule in this study, which eliminated the possible concern about the probiotic organisms being destroyed in the stomach that was raised in the cat study, in which the Azodyl capsules were opened and the product sprinkled on the food. The supplement was also given at twice the manufacturer’s recommended dose. Some of the dogs did have episodes of urinary tract infection during the 12 months of the study and did received short courses of antibiotics, which could potentially interfere with probiotic therapy. But this seems insufficient to entirely invalidate the rather startlingly consistent, negative findings of the study. And since infections are a common and unavoidable problem in kidney failure patients, if the therapy is so easily rendered useless, it would not be of much benefit in the even less controlled conditions of standard clinical use.

Of course, almost no single study should be taken as the final word on any therapy. However, negative results are likely to be more reliable than positive results, and the balance of the evidence is so far pretty negative concerning the usefulness of probiotic therapy for kidney failure. There are theoretical and in vitro study results which suggests that the best one could hope to achieve with probiotic therapy in kidney failure patients is a 10-20% decrease in bloodwork markers of renal failure, which might or might not be sufficient to meaningfully affect the clinical symptoms and the course of the disease. Certainly, in the face of being unable to routinely employ dialysis and transplantation, the most effective therapies available for humans with kidney disease, we should employ any treatment that offers a significant benefit, even a small one. But at this point, it doesn’t look like probiotic therapy holds especially great promise for this disease, unlike some of the other possible conditions in which it might be useful.

In any case, there doesn’t seem to be a strong case for suggesting owners spend their money on this product based on the evidence so far available. And the negative findings so far seen in clinical studies of dogs and cats point out the danger of extrapolating from limited studies in other species. The company-sponsored studies in rats and miniature pigs with artificially induced kidney disease have not proven an accurate indicator of the product’s performance in cats and dogs with naturally occurring kidney failure.

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