Sevelamer hydrochloride binds phosphate released from phytate in chicks fed 1α-hydroxy cholecalciferol

Hyperphosphatemia in animal models of human renal disease has been linked to increased risk of death. Phosphate binders (e.g., sevelamer hydrochloride) and plant-based, low phosphate diets are used to reduce dietary phosphate load; however, animal models show that treatment with active forms of vitamin D(3) (e.g., calcitriol, a renal disease therapy) renders plant phytate phosphate available for absorption. Using an established chick model, the effectiveness of sevelamer in preventing the apparent absorption of liberated phytate phosphate during active vitamin D use was investigated in two separate experiments.

One-day-old chicks were fed ad libitum a basal diet containing deficient levels of inorganic phosphate (0.13%), but adequate in total phosphate (0.40%, 0.23% as phytate phosphate), with or without the inclusion of sevelamer hydrochloride (a phosphate binder), available inorganic phosphate, or active vitamin D as 1α-(OH) D(3).

Plasma phosphate (mg/dL), total bone ash (%), and weight gain (g).

Adding inorganic phosphate (0.36%) or 1α-(OH) D(3) increased plasma phosphate 49% and 48%, respectively (P < .0001), and bone ash 23% and 19%, respectively (P < .001). The addition of 1% sevelamer to the basal diet with added inorganic phosphate or 1α-(OH) D(3) significantly decreased plasma phosphate by 28% and 20%, respectively (P < .01).

Active vitamin D increased the availability of phytate phosphate for intestinal absorption in an animal model; however, sevelamer effectively reduced the availability of phosphate liberated from phytate. These data imply that sevelamer has phytate phosphate binding efficacy.