A crosslinked cation exchange polymer for use in removing potassium from the gastrointestinal (GI) tract of an animal subject, the crosslinked cation exchange polymer comprising acid groups in acid or salt form, the polymer being in the form of substantially spherical particles having a mean diameter of from 20 microns to 200 microns and less than 4 volume percent of the particles have a diameter of less than 10 microns, and the polymer having a sediment yield stress of less than about 4000 Pa, and a swelling ratio of less than 10 grams of water per gram of polymer. Alternatively, the same crosslinked cation exchange polymer is in the form of substantially spherical particles having a mean diameter of less than 250 microns and less than 4 volume percent of the particles having a diameter of less than 10 microns, and the polymer has a swelling ratio of less than 10 grams of water per gram of polymer, and a hydrated and sedimented mass of polymer particles has a viscosity of less than 1,000,000 Pa, the viscosity being measured at a shear rate of 0.01 sec-1. The preferred polymer to be crosslinked is poly(α-fluoroacrylic acid) in salt form. The preferred crosslinking agent is divinylbenzene (DVB). The crosslinked cation exchange polymers have beneficial physical properties, including combinations of particle size, particle shape, particle size distribution, viscosity, yield stress, compressibility, surface morphology, and/or swelling ratio. The polymers may be formulated into pharmaceutical compositions, such as with a linear polyol, especially sorbitol and/or xylitol. These polymers and/or compositions bind to potassium in the GI tract, and are thus are particularly useful for the treatment of hyperkalemia.
