Calcimimetic (Treatment of Hyperparathyroidism)
A calcimimetic is a drug in a class of orally active, small molecules that decrease the secretion of parathyroid hormone (PTH) by activating calcium receptors. The secretion of PTH is normally regulated by the calcium-sensing receptor. Calcimimetic agents increase the sensitivity of this receptor to calcium, which inhibits the release of parathyroid hormone and lowers parathyroid hormone levels within a few hours. Calcimetics are used to treat hyperparathyroidism, a condition characterized by the over-secretion of PTH that results when calcium receptors on parathyroid glands fail to respond properly to calcium in the bloodstream. In March, 2004 the US Food and Drug Administration (FDA) approved the drug cinacalcet (Sensipar), the first calcimimetic, to treat to treat secondary hyperparathyroidism in patients with chronic kidney disease on dialysis, and hypercalcemia in patients with parathyroid cancer. Elevated levels of PTH, the hallmark of secondary hyperparathyroidism, are associated with altered metabolism of calcium and phosphorus, bone pain, fractures, and an increased risk for cardiovascular death. Treatment with cinacalcet lowers serum levels of PTH as well as the calcium x phosphorus ion product. The calcium x phosphorus ion product is a measure of the amount of calcium and phosphorus in the blood, and when elevated, causes harmful deposition of calcium in various parts of the body. Hypercalcemia is associated with parathyroid carcinoma, a rare cancer that causes significant elevations in serum calcium levels. Elevated levels of serum calcium can cause mental confusion, lethargy, dehydration, nausea, vomiting, constipation, and kidney damage.