Binding interactions with sevelamer and polystyrene sulfonate in vitro.

This study explored the binding of 28 drugs, which were selected based on frequency of concomitant use and chemical properties, to sevelamer and polystyrene sulfonate in vitro. The relative binding was determined by dissolving the investigated drugs alone (=control), together with 800 mg of sevelamer and 15 g of polystyrene sulfonate at different pH levels (1.5, 5.5, and 7.4), respectively. After incubation at 37℃ and shaking for 60 min, the solutions were diluted and centrifuged, and the drug concentrations were quantified with validated analytical assays. The binding assays were performed in threefold. The mean relative binding (MRB) at each pH level was calculated, with a MRB >20% for at least one pH level to be considered as relevant binding. Fourteen and 23 potentially new binding interactions were identified with sevelamer and polystyrene sulfonate, respectively. These potentially new binding interactions have to be studied in vivo to assess their clinical relevance.