Eldecalcitol and Osteoporosis

Abstract Eldecalcitol [1α,25-dihydroxy-2β-(3-hydroxypropyloxy)vitamin D3] is an analog of 1α,25-dihydroxyvitamin D3 [1,25(OH)2D3], bearing a hydroxypropyloxy residue at the 2β position. Its chemical structure gives eldecalcitol unique features of actions with long serum half-life, lower affinity but stable binding to vitamin D receptor, and little metabolism via 24-hydroxylation. Eldecalcitol suppresses bone resorption to a greater extent than alfacalcidol by reducing osteoclast number but has a similar effect on bone formation because of resorption-independent minimodeling, resulting in a greater increase in bone mineral density in ovariectomized rats. In osteoporotic patients, eldecalcitol shows stronger effects than alfacalcidol in increasing bone mineral density and reducing bone resorption markers. Once-daily 0.75 μg eldecalcitol reduces the incidence of vertebral fracture compared with 1.0 μg alfacalcidol. In addition, eldecalcitol strongly reduces wrist fracture incidence. It is not known whether eldecalcitol has a stronger effect in preventing falls than alfacalcidol.