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

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.