Practitioner Updates

Pharmacist’s Corner: Effectiveness of Supplements for Cats with Chronic Kidney Disease (CKD)

furry orange cat lying on the floor

Between 2% and 20% of all cats—and 30% of cats over the age of 10—have chronic kidney disease (CKD) (1). There are a handful of risk factors for the development of disease, including prior periodontal disease or cystitis and thin body condition (2).

Currently, medications for CKD are only supportive, including those for appetite stimulation, rehydration, blood pressure control, erythrocyte stimulation, and anti-nausea.

Goals for the development or utilization of new medications would be to help pre­vent, treat, or slow the progression of the disease. Management of phosphorous and toxins with supplements in these patients can be extremely useful, even from early stages.

The table below shows renal supple­ments that have been studied in cats. Based on these studies, Pronefra has the highest chance for consumption, an important consideration given the inap­petence associated with cats experiencing CKD. Pronefra may not currently be available in the US, though it is sold in France and Canada.

Azodyl may not significantly reduce azotemia when sprinkled as opposed to being given as a capsule, a notable point for veterinary prescribers. How­ever, Azodyl is still one of the best-performing products on the market in terms of sales.

RenalTec has been shown to decrease indoxyl sulfate precursors. However, studies have shown that nitrogen-con­taining degradation products play less of a role in the progression of the disease state than dietary phosphorous. The use of these products is supported for slowing the progression of CKD.

SupplementsStudy YearStudy TypeDosingOutcomeNote
Azodyl2007 – 2010ProspectiveSprinkled over food 3 – 4x dailyNo significant difference in treatment vs. placebo groups in BUN or creatinine levels after 4 weeks (3)Study included opening of capsule and sprinkling contents over food – Bacteria were put at risk of deterioration prior to reaching site of action
Azodyl2014Prospective (palatability / prehension*)3 hours after AM meal
Prehension of 59% of cats with 21% of the group consuming 95% or more of the product (4)Noted to be the best performing product of the 4 studied (in sales), but manufacturer’s recommendation to give capsule not followed due to relevance to current practice as the standard is to open capsule and place contents on food
Pronefra2014Prospective (palatability / prehension*)3 hours after AM meal
Prehension of 95% of cats with 38% of the group consuming 95% or more of the product (4)
Statistically significant consumption as compared to all other products studied with the exception of Azodyl
RenalTec2019Prospective500 mg once dailySignificant decrease in serum indoxyl sulfate levels in the treatment group compared to placebo group who had a slight increase in levels after 8 weeks (5)RenalTec consists of precisely adjusted pores that are highly selective for the precursors of uremic toxins
*Voluntarily took the medication into their mouth, whether or not they consumed it.


  1. Lulich JP, Osborne CA, O’Brien RD, Polzin DJ. Feline renal failure: Questions, answers, questions. Compendium on Continuing Education for the Practicing Veterinarian. 1992;14:127–153
  2. Greene JP, Lefebvre SL, Wang M, Yang M, Lund EM, Polzin DJ. Risk factors associ­ated with the development of chronic kidney disease in cats evaluated at primary care veterinary hospitals. J Am Vet Med Assoc. 2014 Feb 1;244(3):320-7. doi: 10.2460/javma.244.3.320. PMID: 24432964
  3. Rishniw M, Wynn SG. Azodyl, a synbiotic, fails to alter azotemia in cats with chron­ic kidney disease when sprinkled onto food. J Feline Med Surg. 2011;13(6):405-409. doi: 10.1016/j.jfms.2010.12.015
  4. Bernachon N, Fournel S, Gatto H, Mong­inoux P, McGahie D. Comparative palat­ability of five supplements designed for cats suffering from chronic renal disease. Ir Vet J. 2014;67(1):10. Published 2014 May 19. doi:10.1186/2046-0481-67-10
  5.­naryDetailer_FINAL.pdf (accessed Nov. 22, 2023)

By Alexandria Arnett

Alexandria Arnett is a Class of 2025 Pharm.D. candidate in the School of Pharmacy at Texas Tech University Health Sciences Center, Dallas.