In Vitro Studies Using Ion Exchange Resins as Potential Phosphaste Binders for Renal Failure Patients

The uptake of phosphate [expressed as phosphorus (P)] by the anion exchange resins, Dowex 1-X8, Dowex SBR, and Bio-Rex 5, aluminum hydroxide, and sucralfate tablets was evaluated. The maximum uptake capacities (in mg P per gram of "wet" resin or solid) were 56, 49, and 84 mg for Dowex SBR, Dowex 1-X8, and Bio-Rex 5 resins, respectively, and 164-168 mg for aluminum hydroxide and sucralfate. At a concentration of P considered to approximate that encountered in the stomach (0.3 mg/ml), Bio-Rex 5 resin, aluminum hydroxide, and sucralfate bound similar amounts of P. Physiologic concentrations of bicarbonate or chloride and simulated gastric or intestinal fluids caused small changes in P uptake by Bio-Rex 5 resin. The resins bound large quantities of taurocholic (TA) and glycocholic (GA) acids. However, when Bio-Rex 5 was converted to the taurocholate form, it bound the same amount of P as the original chloride-form resin, and the binding of TA was prevented.