In
postmenopausal osteoporosis, the administration of
alfacalcidol to women resulted in an increase in trabecular bone
mineral density (BMD), prevention of cortical bone loss, and a significant reduction in the incidence of further vertebral fractures. There is now robust evidence that
alfacalcidol may be particularly active in conditions characterized by an increased rate of bone loss.
Alfacalcidol 1 microg/day fully prevented vertebral bone loss over 3 years in women after the first year of menopause. In a large cohort of individuals starting treatment with high dose
corticosteroid (CS, 46.6 mg equivalent
prednisolone per day), the spinal bone loss observed in untreated patients was fully prevented by administration of 1 microg/day
alfacalcidol. In patients with established CS-induced
osteoporosis, with or without prevalent vertebral fractures, 1 microg/day of
alfacalcidol, given for 3 years, increased lumbar spine density, reduced
back pain, and showed a significant reduction in the rate of new vertebral fractures, compared to native
vitamin D. In cardiac transplant recipients,
alfacalcidol and
calcium reduced spinal and femoral bone loss, compared to a control group treated with
etidronate and
calcium.
Alfacalcidol-treated patients experienced fewer new vertebral fractures over the 2-year followup. When
alfacalcidol and
vitamin D3 were compared in elderly women with radiologic evidence of vertebral fracture, fractional
calcium absorption was increased after 3 months with
alfacalcidol but was unchanged with
vitamin D3. In a recent metaanalysis of 14 studies of native
vitamin D and 19 studies of D-
hormone analogs (
alfacalcidol and
calcitriol), the D-analogs exerted a higher preventive effect on bone loss and fracture rates in patients with no exposure to CS. In head-to-head studies comparing D-analogs and native
vitamin D in patients receiving CS, this metaanalysis identified significant effects favoring D-analogs for femoral neck BMD and
spinal fractures. In conclusion, improvement in bone turnover, increase in BMD, and reduction in fracture rates have been described during
alfacalcidol treatment in situations characterized by a high rate of bone loss, including CS-induced
osteoporosis, early
postmenopausal bone loss, and organ transplant. Compared to plain
vitamin D,
alfacalcidol exerts higher bone-protective effects, thus allowing the doses to be minimized and lowering the risk of adverse effects, including
hypercalcemia.