EFFECT OF RENAGEL(R), A NONABSORBABLE, CROSS-LINKED, POLYMERIC PHOSPHATE BINDER, ON URINARY PHOSPHORUS EXCRETION IN RATS

Background. Normalization of serum phosphorus is critical in the treat ment of End Stage Renal Failure patients. Aluminum or calcium based ph osphate binders, while efficacious, are associated with potential adve rse side effects and toxicities. We have developed RenaGel(R), a novel , non-absorbed hydrogel which binds dietary phosphate leading to incre ased fecal excretion, decreased absorption and decreased serum phospho rus levels. In this paper, we present results from both in vitro and i n vivo studies in which we examined the efficacy of this novel phospha te binder. Methods. In vitro, RenaGel(R) was suspended in the test sol ution, and the mixture was stirred for 1 hour at room temperature. The solid was then filtered off, and the residual liquid analyzed for pho sphate. In vivo, RenaGel was mixed in rodent feed at different concent rations and fed to normal rats for up to 4 days. Urine was collected a nd analysed for phosphate content. Results and conclusions. In vitro b inding studies demonstrate that RenaGel has an extremely high phosphat e binding capacity. At an estimated physiological concentration of 5 m M phosphate, RenaGel binds 2.6 mmole phosphate/g of phosphate binder. The in vivo binding study shows that RenaGel mixed into the diet decre ased urinary phosphorus excretion in a dose dependent manner. RenaGel particles with a 23 mu m mean diameter are more efficacious than the l arger ones. In conclusion, the above studies indicate that RenaGel is a potent phosphate binder. RenaGel(R) contains no calcium or aluminum and offers an alternative to existing phosphate binder treatments.