The influence of dialysate calcium on the therapeutic effects of sevelamer hydrochloride in hemodialysis patients with secondary hyperparathyroidism under treatment of intravenous vitamin D metabolites

The management of hyperphosphatemia is essential to treat secondary hyperparathyroidism and to prevent ectopic calcification. Sevelamer hydrochloride (sevelamer), a new phosphate binder that contains neither aluminum nor calcium, which could be theoretically beneficial for the management of hyperphosphatemia in dialysis patients with secondary hyperparathyroidism who are receiving intravenous vitamin D metabolites (maxacalcitol or calcitriol). To reduce calcium loads, a dialysate calcium concentration of 2.5 mEq/L is recommended by Kidney Disease Outcome Quality Initiative (K/DOQI) guidelines. In Japan, a dialysate calcium concentration of 3.0 mEq/L prevails. We investigated the influence of dialysate calcium on the therapeutic effect of sevelamer in 40 hemodialysis patients who are under treatment of intravenous vitamin D metabolites for secondary hyperparathyroidism (VD(+)) and compared the results with those of 41 patients who had not received vitamin D metabolites (VD(-)). Serum phosphorus and calcium-phosphorus products showed no significant change by sevelamer in either the VD(+) subgroup of patients receiving hemodialysis with dialysate calcium of 2.5 mEq/L (DCa2.5) or those receiving hemodialysis with dialysate calcium of 3.0 mEq/L (DCa3.0), while serum phosphorus and calcium-phosphorus products decreased in both the VD(-) subgroups. Serum calcium decreased in the DCa2.5 subgroup and did not change in the DCa3.0 subgroup in both the VD(+) and the VD(-) subjects. Parathyroid hormone and alkaline phosphatase increased in the DCa2.5 subgroup and did not change in the Ca 3.0 subgroup in the VD(+) subjects. Serum calcium decreased in both subgroups in the VD(-) subjects. Parathyroid hormone obtained after sevelamer administration in the VD(-) group was within the target range of the K/DOQI guidelines. In conclusion, the concomitant use of sevelamer as a phosphate binder and the dialysate of calcium concentration of 2.5 mEq/L have possibilities for worsening secondary hyperparathyroidism in patients receiving intravenous vitamin D.