Sevelamer (Renagel) is an aluminum- and calcium-free phosphate binder used in the treatment of hyperphosphatemia in end-stage renal disease. Sevelamer is a cationic polymer (poly[allylamine hydrochloride]) cross-linked with epichlorohydrin, which binds phosphate anions by ion exchange and hydrogen binding. Although sevelamer is hydrophilic, it is not absorbed by the gastrointestinal tract. When the polymer comes in contact with gastric or intestinal fluid, it expands through hydration; it can expand up to eight times its weight. This gelatinous form binds phosphate in the gastrointestinal tract and then is excreted in feces. This polymer cannot be crushed or broken prior to ingestion because an intact gelatinous matrix is needed for efficient phosphate binding.