Patent ID: 8617609

Claim:
A pharmaceutical composition for removing potassium ion from a gastrointestinal tract of a mammal, the pharmaceutical composition comprising a pharmaceutical excipient and a core-shell particle, the core-shell particle comprising a core polymer and a shell polymer, the core polymer having a capacity for binding potassium ion, the shell polymer having a persistent selectivity for potassium ion over magnesium ion, the pharmaceutical composition having a specific binding for potassium ion of at least 1.5 mmol/gm achieved within a potassium-binding period of less than 18 hours, and the pharmaceutical composition having a specific binding for magnesium ion of not more than 1.0 mmol/gm maintained over a magnesium-binding period of more than 18 hours, as determined in vitro in an assay selected from the group consisting of (i) a first assay consisting essentially of incubating the pharmaceutical composition at a concentration of 4 mg/ml in a solution consisting essentially of 55 mM KCl, 55 mM MgCl 2 and 50 mM 2-morpholinoethanesulfonic acid, monohydrate, at a pH of 6.5 and a temperature of 37Â° C. for 48 hours with agitation, and directly or indirectly measuring cations bound to the pharmaceutical composition over time, (ii) a second assay consisting essentially of incubating the pharmaceutical composition at a concentration of 4 mg/ml in a solution consisting essentially of 50 mM KCl, 50 mM MgCl 2 , 50 mM 2-morpholinoethanesulfonic acid, monohydrate, 5 mM sodium taurocholate, 30 mM oleate and 1.5 mM citrate, at a pH of 6.5 and a temperature of 37Â° C. for 48 hours with agitation, and directly or indirectly measuring cations bound to the pharmaceutical composition over time, and (iii) a third assay consisting essentially of incubating the pharmaceutical composition at a concentration of 4 mg/ml in fecal water solution, the fecal water solution being a filtered centrifugal supernatant derived by centrifuging human feces for 16 hours at 50,000 g at 4Â° C. and then filtering the supernatant through a 0.2 um filter, the pharmaceutical composition being incubated in the fecal water solution at a temperature of 37Â° C. for 48 hours with agitation, and directly or indirectly measuring cations bound to the pharmaceutical composition over time, and combinations of one or more of the first assay, the second assay and the third assay; the core polymer being a crosslinked cation exchange polymer and the shell polymer being a crosslinked polyvinylamine polymer represented by Formula I: wherein n is at least 4, and R 1 and R 2 are independently hydrogen, alkyl, or aryl.