Calcium carbonate (CaCO3): an efficient and safe phosphate binder in haemodialysis patients? A 3-year study.

In an uncontrolled study, 22 dialysis patients (46 +/- 14 years, duration of dialysis 20 +/- 11 months) were treated with CaCO3 over a period of up to 3 years to lower their serum phosphate. The use of 4.5-9 g CaCO3 daily over a period of 9 months led to a reduction of mean serum phosphate from 2.51 to 1.51 mmol/l in 77% of patients, with a simultaneous increase in mean calcium concentration from 2.23 to 2.47 mmol/l, and an improved control of secondary hyperparathyroidism by reduction in mPTH from 1552 to 1032 pg/ml and in APH activity from 6.25 to 4.55 mumol/s/l. In long-term CaCO3 treatment of up to 3 years, however, a constant effective phosphate reduction could not be achieved. There was a progression (77%) of pre-existing microcalcification and a new appearance (42%) of microcalcification in vessels and soft-tissue areas of the hand. The percentage of patients with soft-tissue calcification increased from 43 to 67% during a treatment period of 3 years. We conclude that CaCO3 alone is not suitable on a long-term basis for phosphate reduction in dialysis patients.