Comparative effect of eldecalcitol and alfacalcidol on bone microstructure: A preliminary report of secondary analysis of a prospective trial.

Abstract Objectives To compare the effect of eldecalcitol and alfacalcidol on skeletal microstructure by high-resolution peripheral QCT (HR-pQCT). Methods This was a substudy of a randomized, double-blind, active comparator trial. Five female osteoporotic patients with 1-year 0.75 μg/day eldecalcitol and 5 with 1-year 1.0 μg/day alfacalcidol completed HR-pQCT scans before and after treatment were enrolled. Results Total vBMD [1.67 ± 1.06% (mean ± SD), P = 0.043 versus baseline] and trabecular vBMD (2.91 ± 1.72%, P = 0.043) at the radius increased in eldecalcitol group, while total, trabecular, and cortical vBMD tended to decrease in alfacalcidol group, with a significant reduction in cortical vBMD at the tibia (0.88 ± 0.62%, P = 0.043). Cortical area (1.82 ± 1.92%, P = 0.043) at the radius and thickness (0.87 ± 1.12%, P = 0.043) at the tibia increased in eldecalcitol group, while these parameters decreased with alfacalcidol at the tibia (1.77 ± 1.72%, P = 0.043 for cortical area; 1.40 ± 2.14%, P = 0.042 for cortical thickness). Trabecular thickness at the radius (1.97 ± 1.93%, P = 0.042) and number at the tibia (3.09 ± 3.04%, P = 0.043) increased by eldecalcitol but did not increase by alfacalcidol. Trabecular separation decreased by eldecalcitol (2.22 ± 2.43%, P = 0.043) but tended to increase by alfacalcidol at the tibia. Conclusions Eldecalcitol has the greater potential to improve cortical and trabecular microstructure at the peripheral bone than alfacalcidol which needs further more studies.