These agents work by binding to phosphate in the GI tract, thereby making it unavailable to the body for absorption.
Hence, these drugs are usually taken with meals to bind any phosphate that may be present in the ingested food.
Phosphate binders may be simple molecular entities (such as magnesium, aluminium, calcium, or lanthanum salts) that react with phosphate and form an insoluble compound.
Calcium carbonate Calcium-based phosphate binders, such as calcium carbonate, directly decrease phosphate levels by creating insoluble calcium–phosphate complexes which gets eliminated in the feces.
[1] For people with chronic kidney failure, controlling serum phosphate is important because it is associated with bone pathology and regulated together with serum calcium by the parathyroid hormone (PTH).