Long-term comparison of a calcium-free phosphate binder and calcium carbonate - phosphorus metabolism and cardiovascular calcification

Abstract

Calcium carbonate used as a phosphate binder may contribute to cardiovascular calcification. Long-term comparisons of sevelamer, a non-calcium polymeric phosphate binder, and calcium carbonate (CC) are lacking. 114 adult hemodialysis patients were randomly assigned to open label sevelamer or CC for 52 weeks. Study efficacy endpoints included changes in serum phosphorus, calcium, calcium-phosphorus product, and lipids. In addition, initial and sequential electron beam computerized tomography scans were performed to assess cardiovascular calcification status and change during follow-up. Safety endpoints were serum biochemistry, blood cell counts and adverse events. Patients receiving sevelamer had a similar reduction in serum phosphorus as patients receiving CC (sevelamer -0.58 +/- 0.68 mmol/l, CC -0.52 +/- 0.50 mmol/l; p = 0.62). Reductions in calcium-phosphorus product were not significantly different (sevelamer -1.4 +/- 1.7 mmol2/l2, CC -0.9 +/- 1.2 mmol2/l2; p = 0.12). CC produced significantly more hypercalcemia (> 2.8 mmol/l in 0% sevelamer and 19% CC patients, p < 0.01) and suppressed intact parathyroid hormone below 150 pg/ml in the majority of patients. Sevelamer patients experienced significant (p < 0.01) reductions in total (-1.2 +/- 0.9 mmol/l, -24%) and LDL cholesterol (-1.2 +/- 0.9 mmol/l, -30%). CC patients had significant increases in coronary artery (median +34%, p < 0.01) and aortic calcification (median +32%, p < 0.01) that were not observed in sevelamer-treated patients. Patients on sevelamer required more grams of binder (sevelamer 5.9 g vs. CC 3.9 g) and experienced more dyspepsia than patients on calcium carbonate. Sevelamer is an effective phosphate binder that unlike calcium carbonate is not associated with progressive cardiovascular calcification in hemodialysis patients.