Long-Term (6 Months) Cross-Over Comparison of Calcium Acetate with Calcium Carbonate as Phosphate Binder

Abstract

A previous short-term study of 10 weeks in 8 patients had shown us that with half the dose of elemental calcium, calcium acetate (CaAc) could control predialysis plasma phosphate (PPO₄) as well as calcium carbonate (CaCO₃) but that the incidence of hypercalcemia was not decreased. To better appreciate the value of CaAc in comparison to CaCO₃, CaAc was given to 28 patients on chronic hemodialysis (6 men, 22 women, age 61 ± 14 years; dialyzate Ca: 1.5 mmol/l) for 6 months to replace CaCO₃ at half the dose of elemental calcium (1,235 ± 521 versus 2,375 ± 1,470 mg/day). Because of gastrointestinal intolerance, CaAc had to be discontinued in 5 patients after 1-5 months. Magnesium hydroxide [Mg(OH)₂] given in 18 of them in association with CaCO₃ was discontinued and reintroduced in 6 patients in order to keep PPO₄ < 2 mmol/l. Mean dosage of Mg(OH)₂ was 2.09 ± 1.4 g/day with CaCO₃ and 0.9 ± 0.5 with CaAc. Predialysis plasma concentrations of calcium and phosphate were monitored weekly during the 3 months of the control period under CaCO₃ and during the 6-month administration of CaAc. Plasma calcium (PCa) was comparable with the 2 treatments (2.47 ± 0.11 vs. 2.5 ± 0.10 mmol/l), but PPO₄ was significantly lower with CaAc (1.82 ± 0.26 vs. 1.73 ± 0.23 mmol/l). Plasma alkaline phosphatase remained constant (122 ± 66 vs. 122 ± 70; normal < 170 UI/l) as well as plasma intact PTH (121 ± 153 vs. 121 ± 146; normal < 54 pg/ml) and plasma aluminum (0.34 ± 0.23 vs. 0.32 ± 0.20 μmol/l). Hypercalcemia (PCa > 2.7 mmol/l) was present in 11 patients with CaCO₃ and in 16 patients with CaAc, and its incidence did not decrease with CaAc (8.2 vs. 8%). In conclusion, this long-term study confirms that CaAc is a more efficient PO₄binder than CaCO₃. However, its gastrointestinal tolerance seems poorer and the incidence of hypercalcemia is not decreased. The paradox of the unchanged incidence of hypercalcemia with acetate in spite of a reduction by half of the amount of calcium ingested may have two explanations: the very presence of a lower plasma PO₄ concentration (by a physicochemical mechanism) and the possible greater bioavailability of the calcium for absorption when it is given as CaAc.

Calcium acetate versus calcium carbonate as oral phosphate binder in pediatric and adolescent hemodialysis patients

“…Results of different calcium acetate studies in adults are not conclusive, demonstrating both a significant decrease [20] and increase [19,21,28] or even no change [24] in the incidence of hypercalcemia. Different medication with vitamin D metabolites may in part account for these differences.…”

“…Several studies in adult patients on chronic hemodialysis have shown calcium acetate to be superior to calcium carbonate in its ability to control hyperphosphatemia [12,[19][20][21][22][23][24][25][26][27][28]. The amount of orally ingested calcium taken as calcium acetate needed to bind phosphorus effectively is between 49% and 83% of that ingested with calcium carbonate [19,21,29].…”

“…Caravaca et al [21] and Pflanz et al [27] prescribed no vitamin D metabolites at all, Moriniere et al [19] prescribed 74 ~g/week 25(OH)D3, and Schaefer et al [20] investigated three groups with no 1,25(OH)2D3, with 0.5 ~tg/ day, or 4 ~tg twice a week. Furthermore, the definition of hypercalcemia varied between the studies: >2.7 mmol/1 [24,27,28], >2.75 mmol/1 [19,29], >2.86 mmol/1 [21], and > 3 mmol/l [20]. There was a tendency towards a higher incidence of hypercalcemia in studies using vitamin D metabolites.…”

“…Clinical studies in adult hemodialysis patients have shown calcium acetate to be more potent than calcium carbonate [12,[18][19][20][21][22][23][24][25][26][27][28] and the oral dose of elementary calcium could be reduced by 50% [12,[19][20][21][22][23][24][25][26]29]. Results concerning reduction of the incidence of hypercalcemia have been conflicting.…”

Phosphate binders for control of phosphate retention in chronic renal failure

“…However, hypercalcemia is more frequently observed with calcium carbonate than with calcium acetate [72,74]. Calcium acetate is poorly tolerated so that patient compliance may be worse than with calcium carbonate [73,75]. In patients on hemodialysis, concurrent use of a low-calcium dialysate (1.25 mmol/l) has significantly reduced the incidence of hypercalcemia with both of these calcium-based P i binders [76,77].…”