To accomplish this, it is important to administer the oral calcium salt with meals or snacks because it exerts minimal effects on phosphate once phosphate has been absorbed into the circulation. Calcium binds with phosphate in the gut, forming the insoluble calcium phosphate, which is subsequently eliminated in the stool. Some free calcium, however, can be absorbed, potentially elevating the calcium-phosphorus product. For this reason, it is important to avoid using calcium salts as phosphate binders when serum phosphorus is extremely elevated. Small amounts of calcium and bicarbonate are absorbed, however, which can cause hypercalcemia.
Calcium is excreted in the urine.
Hypercalciuria is common in patients receiving calcium carbonate therapy. Patients with preexisting hypercalcemia, renal disease, or dehydration are predisposed to developing milk-alkali syndrome. Calcium blood concentrations should be monitored weekly in patients receiving calcium carbonate therapy. Administration of calcium carbonate can cause gastric hypersecretion and acid rebound. For this reason, calcium carbonate is not a good choice for the treatment of peptic ulcer disease.