Doxercalciferol is a synthetic vitamin D2 analog that undergoes metabolic activation in vivo to form 1α,25-dihydroxyvitamin D2 (1α,25-(OH)2D2), a naturally occurring, biologically active form of vitamin D2. Doxercalciferol is indicated for the treatment of secondary hyperparathyroidism in patients with chronic kidney disease on dialysis, as well as for the treatment of secondary hyperparathyroidism in patients with Stage 3 or Stage 4 chronic kidney disease. Doxercalciferol is marketed under the brand name Hectorol by Genzyme Corporation, and is manufactured by Catalent Pharma Solutions, Inc.

1,25-dihydroxycalciferol (1,25-dihydroxyvitamin D2 or ercalcitriol) is a metabolite of vitamin D. It exerts antirachitic activity in animals. 1,25-dihydroxycalciferol and its analogs have antineoplastic actions in vitro.