An in vitro crystallization setup to assess the efficiency of different phosphate binders in nephrology: quantitative analytical considerations

An increased phosphate level in the blood (hyperphosphatemia) is a severe problem for dialysis patients. Different phosphate binders which are used to prevent hyperphosphatemia were studied in a custom-made in vitro crystallization apparatus which simulated the stomach (pH 2) and the gut (pH 7). The effective phosphate binding capacity was measured and the resulting products were identified. This apparatus permits the quantitative analysis of the phosphate binding effect under the given in vitro conditions. In particular, phosphate binders on the basis of calcium acetate (Calciumacetat Nefro®), calcium carbonate (Calciumcarbonat® Fresenius), aluminium hydroxide (Antiphosphat®), lanthanum carbonate (Fosrenol®), and poly(allylamine hydrochloride) (Renagel®) were studied, and also compared with pure calcium acetate, calcium carbonate, and aluminium sulfate.