Calcium acetate versus calcium carbonate in chronic haemodialysis

Summary: The purpose of this study was to compare the efficacy of calcium acetate (CA) and calcium carbonate (CC) as phosphate binders in patients on maintenance haemodialysis. A randomized, blinded, crossover study was conducted for 24 weeks in 32 subjects who were stabilized on in-centre haemodialysis with low calcium (1.25 mmol/L) dialysate, were using calcium carbonate as their primary phosphate binder and had a pre-dialysis serum phosphate level of ± 1.85 mmol/L. Subjects were randomized to receive CA or CC for a period of 12 weeks, followed by the other treatment for 12 weeks; Mylanta II was added as required to achieve adequate phosphate control. There were no differences in mean serum calcium or phosphate during treatment with CA and CC, and serum parathyroid level was unchanged with both. There were four episodes of hypercalcaemia (serum Ca²⁺ > 2.70 mmol/L) while on CA compared with 11 on CC ( P = NS), and seven episodes of hyperphosphataemia (serum P₁± 2.00 mmol/L) on CA compared with 21 on CC ( P = 0.02). Signfficantly more Mylanta II was prescribed with CC than with CA after 8 or more weeks ( P <0.05). the dose of elemental Ca²⁺ ingested with CC was twice that with CA. Calcium acetate was less well tolerated than CC, and five patients withdrew from the trial because of side-effects with CA, and one with CC. In conclusion, among haemodialysis patients who can tolerate it, CA is a superior phosphate binder to CC.