The effectiveness of a soluble calcium preparation as a gut phosphate binder

We determined the phosphate binding capacity of a soluble commercial calcium preparation by carrying out metabolic balances on four normal subjects and by administering it for 4 weeks to six patients treated by maintenance hemodialysis. Each tablet of Sandocal 1000 (Sandoz, Australia) contained 1 g of elemental calcium as calcium lactate-gluconate 5.23 g and calcium carbonate 0.8 g. The metabolic balance study was performed over two consecutive nine-day periods. A constant, normal diet was consumed throughout, but in the second period one Sandocal 1000 tablet was added to each of the three major daily meals. Each period consisted of four days of equilibrium, then five days of collection of urine and feces. Polyethylene glycol 4,000 was used as a continuous fecal marker and carmine red was used to indicate gut transit time. Calcium supplementation increased fecal phosphate excretion by 11.2 +/- 2.3 mmol/d (SD), and decreased urinary phosphate by 8.4 +/- 2.6 mmol/d. Plasma calcium levels were unchanged, while plasma phosphate levels rose slightly. The increase in fecal phosphate was similar to that previously reported when calcium carbonate 8 g/d or aluminum hydroxide 6.4 g/d were administered. In the patients treated by maintenance hemodialysis, the reduction in plasma phosphate induced by Sandocal 1000, three tablets daily, was similar to that obtained with aluminum hydroxide 1.8 +/- 1.2 g/d. Hence, this calcium preparation appears to have a phosphate binding capacity similar to that of standard doses of aluminum hydroxide.