Effects of an Intestinal Phosphorus Binder on Serum Phosphorus and Parathyroid Hormone Concentration in Cats With Reduced Renal Function

Ten young adult cats, 6 intact males and 4 intact females, with reduced renal mass were randomized to receive either normal feline maintenance diet alone or diet plus phosphorus binder in a crossover design with each treatment period of 56 days in duration (Dietary Trial A). For Dietary Trial B, following a 3-month withdrawal period, 6 cats were placed on the intestinal phosphorus binder for 9 months to determine the longterm effects of this approach. During both Dietary Trials A and B, cats were studied by serum and urine biochemical testing and renal clearance studies. In Dietary Trial A, compared to diet alone, serum phosphorus and plasma parathyroid hormone concentrations were significantly lower when intestinal phosphorus binder was provided. There were no significant differences in blood urea nitrogen, serum creatinine concentration, glomerular filtration rate, or renal plasma flow. In Dietary Trial B, serum phosphorus and plasma parathyroid hormone concentrations were reduced at the 6and 9-month time points of the treatment period compared to measurements obtained before intestinal phosphorus binder administration. We conclude that the addition of an intestinal phosphorus binder to a normal maintenance feline diet can lower serum phosphorus and parathyroid hormone concentrations in cats with International Renal Interest Society stages I and II chronic kidney disease. The effect of the binder to reduce serum phosphorus concentration was present by Day 56 in Dietary Trial A and persisted at 6 and 9 months in Dietary Trial B.