Because sodium polystyrene sulfonate is not orally absorbed, it is unlikely to reach the breastmilk or adversely affect the breastfed infant after maternal administration. No special precautions are required.
A suspension of sodium polystyrene sulfonate has been added directly to breastmilk to lower the potassium concentration of milk for use in infants with renal impairment. In addition to lowering average potassium content by 65%, the calcium content of breastmilk was reduced by 84%.[1] Infants given either expressed breastmilk, formula or a combination of both had their average serum potassium levels decreased by 24% from 6.3 to 4.8 mEq/L. Serum calcium and creatinine also decreased slightly. The infants had no clinically noticeable side effects.[2] Addition of large amounts of sodium polystyrene sulfonate to artificial formula also lowers the calcium, copper, manganese, phosphorus, sulfur and zinc concentrations; whereas the iron, sodium and sulfur content of formulas are increased.[3] Similar changes might occur with breastmilk.