Calcium acetate versus calcium carbonate as phosphate-binding agents in chronic haemodialysis

Hyperphosphataemia plays a key role in the pathogenesis of renalosteodystrophy, and phosphate-binding agents are required inmany chronic dialysis patients. Aluminium hydroxide and calciumcarbonate are well-established phosphate binders, but theiruse is associated with toxicity or poor efficacy. Calcium acetateis known to be a potent phosphate binder, and has recently beenused successfully in chronic dialysis patients. In this randomizedcross-over trial in 31 chronic haemodialysis patients, equimolardoses of calcium acetate and calcium carbonate were administeredfor 6 weeks each. Compliance was estimated from tablet counts,and biochemical parameters were measured at the end of eachtreatment period. Of the 31 patients 23 completed both treatmentarms; of the remainder, three withdrew due to adverse symptoms,hypercalcaemia necessitated treatment withdrawal in two, andthree died. Non-compliance was significantly higher with acetate(18.3% tablets not taken) than with carbonate (8.7%). Serumphosphate was significantly lower after treatment with acetate(1.51 mmol/l) than with carbonate (1.80), as was the Ca x PO₄product (3.59 vs 4.18 respectively) and PTH (17.8 vs 25.4 pmol/lrespectively). Serum calcium was significantly higher afteracetate therapy (2.40 vs 2.32 mmol/l). No significant differencewas found for sodium, potassium, bicarbonate, urea, creatinine,and haemoglobin. This study confirms that the treatment of hyperphosphataemiais more effective with calcium acetate than with calcium carbonate.For the first time an associated beneficial effect on secondaryhyperpara thyroidism has also been demonstrated. Patient tolerability of calcium acetate was considerably poorer, probablydue in part to tablet formulation and bulkiness, as well aspossible direct gastrointestinal effects of the acetate salt.