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Pharmacology: Pharmacodynamics: Calcium polystyrene sulfonate, the calcium salt of sulfonated styrene polymer, is not absorbed from gastrointestinal tract. Calcium polystyrene sulfonate is a cations-exchange resin that exchanges calcium ions for potassium ions and other cations in the gastrointestinal tract (it is estimated that 1 g of calcium polystyrene sulfonate could bind 1.3 to 2 mmol of potassium).
Pharmacokinetics: Calcium is absorbed from GI tract by passive diffusion and active transport. Calcium absorption is increased in the presence of food. Oral bioavailability in adults ranges from 25% to 35% when a 250 mg dose is given with a meal. Absorption from milk was 29% under the same conditions. Normal total serum calcium concentrations range from 9 to 10.4 mg/dL (4.5 to 5.2 mEq/L), but only ionized calcium is active. Calcium crosses the placenta and distributed into milk. Calcium is mainly excreted in the faces. Only small amounts are excreted in the urine.
