Effects of anion exchange resin as phosphate binder on serum phosphate andiPTH levels in normal rats

In order to investigate the characteristics of anion exchange resins that m ay safely and effectively bind dietary phosphate in digestive tract, phosph ate binding experiments were carried out in vitro and in vivo with normal r ats by comparing anion exchange resins, PAA-B (which has the same chemical structure as Sevelamer(R) HCl) and Dowe 1x8, with CaCO3. In in vitro phosph ate binding experiments, PAA-B bound 32.3% less phosphate than CaCO3 at pH 7 In the rat dietary phosphorus excretion experiments, PAA-B, Dowex 1x8, an d CaCO3 increased fecal phosphorus excretion by 62.7 32.3 and 84.0%, respec tively. Famotidine significantly reduced the phosphate binding of CaCO3. Wh en phosphate solution was orally adiministered, PAA-B depressed serum phosp horus augmentations immediately after administration and thereafter effecti vely depressed serum iPTH. This suggests that anion exchange resins with mo st primary and secondary amino type anion exchange groups, have bright pros pects in the treatment of hyperphosphatemia.