Effect of the Time of Administration of Calcium Acetate on Phosphorus Binding

Abstract

Phosphorus binders are given to patients with renal failure to increase gastrointestinal excretion of phosphorus. To determine the relative importance of the binding of dietary as compared with endogenous phosphorus and to determine the optimal dose schedule, we gave either 4.4 g of calcium acetate (25 mmol of calcium) or a placebo to six normal subjects on each of seven different schedules in a randomized sequence. The net gastrointestinal balance of phosphorus and calcium was determined by a one-day lavage technique. After a meal containing approximately 12 mmol of phosphorus, the mean phosphorus absorption (+/- SE) measured 9.17 +/- 0.36 mmol (78 percent) with placebo but decreased to 3.81 +/- 0.58 mmol (31 percent) when calcium acetate was given immediately before the meal (representing binding of 5.36 +/- 0.77 mmol of phosphorus). Similar binding was observed when calcium acetate was given immediately after the meal and when half the dose was given before and half after the meal. In contrast, when calcium acetate was given two hours after the meal or while the subject was fasting, phosphorus binding was reduced to 2.00 +/- 0.52 mmol and 1.81 +/- 0.84 mmol, respectively. Calcium absorption from calcium acetate averaged 21 +/- 1 percent when the binder was given with a meal; absorption from calcium acetate averaged 40 +/- 4 percent when the binder was given while the subject was fasting. We conclude that calcium acetate increases fecal excretion of phosphorus by binding both dietary and endogenous phosphorus, but the binding of dietary phosphorus is quantitatively much more important. For the most efficient phosphorus binding, calcium (and presumably other phosphorus-binding cations) should be given with meals.

Phosphate binders in patients with chronic kidney disease

“…As with all phosphate binders, calcium-based binders are most effective when taken with meals (which also limits calcium absorption). 10 They should be prescribed in conjunction with moderate dietary phosphate restriction, ideally supervised by an accredited practising dietitian. Phosphate-rich foods with a high phosphate to protein ratio (processed foods, fast foods and cola drinks) are best avoided, while foods with a high biologic value (e.g.…”

Control of Hyperphosphatemia among Patients with ESRD

“…Moreover, the temporal relationship with meals is crucial to bind dietary phosphate adequately. It is well established that unsynchronized administration of binders significantly increases the proportion of dietary phosphorus absorbed compared with concomitant administration of binder with meals (24,35,36,46,87).…”

Calcium and Phosphate Plasma Levels in Dialysis Patients after Dietary Ca-P Overload

“…So, many efforts have been aimed to design low phosphate diets and to evaluate new phosphate-binding agents, tailoring their administration in relation to the dietary phosphate intake [8]. Previous studies demonstrated that 70% of the absorbed dietary phosphate is actively transported in duodenum and jejunum by an Na-dependent co-transport mechanism; the other 30% is passively absorbed in the same intestinal segments by diffusion [9].…”