Paricalcitol (marketed by Abbott Laboratories under the trade name Zemplar) is a drug used for the prevention and treatment of secondary hyperparathyroidism (excessive secretion of parathyroid hormone) associated with chronic renal failure. Chemically, it is 19-nor-1,25-(OH)2-vitamin D2 or 19-nor-1,25-dihydroxyvitamin D2, being an analog of 1,25-dihydroxyergocalciferol, the active form of vitamin D2. From Wikipedia