Phosphate binders for control of phosphate retention in chronic renal failure.

In patients with chronic renal insufficiency, phosphate retention is a major factor in the development of secondary hyperparathyroidism, renal osteodystrophy, and soft tissue calcification, and may contribute to progression of renal failure. Prevention of phosphate retention with dietary and pharmacological means, along with the administration of calcitriol, may prevent or reverse secondary hyperparathyroidism. With more-advanced renal failure, phosphate binders become necessary to maintain phosphate balance and to prevent hyperphosphatemia. Because of toxicity, aluminum-containing phosphate binders are no longer used. Currently, calcium-containing phosphate binders, such as calcium carbonate and calcium acetate, are the most widely prescribed. Although calcium salts eliminate the problems associated with aluminum toxicity, they often result in transient hypercalcemia, requiring discontinuation of calcitriol and the use of low-calcium dialysate. Several new non- aluminum- and non-calcium-containing phosphate binders are currently at various stages of development, and may provide an alternative to the currently used binders. It is unlikely, however, that the newer compounds will completely replace calcium salts, since mild hypercalcemia may be necessary in chronic renal failure patients to suppress parathyroid hormone production. Other areas of investigation must include the development of drugs to inhibit soft tissue and renal calcifications, and to enhance urinary phosphate excretion.