Calcitriol(1,25-Dihydroxyvitamin D3; Rocaltrol ) is the hormonally active form of vitamin D.Active metabolite of vitamin D3 that activates the vitamin D receptor (VDR).Calcitriol(1,25-Dihydroxyvitamin D3; Rocaltrol ) displays calcemic actions. Calcitriol stimulates intestinal and renal Ca2+ absorption and regulates bone Ca2+ turnover. Calcitriol (1,25-Dihydroxyvitamin D3; Rocaltrol )exhibits antitumor activity; Calcitriol(1,25-Dihydroxyvitamin D3; Rocaltrol ) inhibits in vivo and in vitro cell proliferation in a wide range of cells including breast, prostate, colon, skin and brain carcinomas and myeloid leukemia cells.