A comparison of the effects of alfacalcidol treatment and vitamin D-2 supplementation on calcium absorption in elderly women with vertebral fractures

Although vitamin D supplementation in the frail elderly improves calcium absorption, suppresses parathyroid hormone, decreases bone loss and reduces I-he risk of fractures, such treatment may be ineffective in patients with vertebral osteoporosis, because of impaired vitamin D metabolism or resistance to the action of vitamin D metabolites on the bowel, We have therefore performed a randomized, single masked study comparing the effects of alfacalcidol treatment (0.25 mu g twice daily) and vitamin D-2 supplementation (500-1000 units daily) on calcium absorption and bone turnover in 46 elderly ii omen (median age 69 years, range 64-79 years) with radiological evidence of vertebral fractures. Serum 25-hydroxyvitamin D increased significantly after 3 and 6 months of treatment with vitamin D-2 (p<0.001), but was unchanged in the group receiving alfacalcidol. Serum 1,25-dihydroyvitamin D did not change significantly in either group over the study period. Fractional Ca-45 absorption increased after 3 months of treatment with alfacalcidol (P<0.05), but was unchanged with vitamin D-2. There was also a reduction in plasma intact parathyroid hormone and serum alkaline phosphatase after 6 months of treatment with alfacalcidol (p<0.05) which was nor seen in the group receiving vitamin D-2. Our study shows that vitamin D-2 supplementation is ineffective ill stimulating calcium absorption in elderly women with vertebral osteoporosis. By increasing calcium absorption in such patients, alfacalcidol may prove more effective than Vitamin D in the management of vertebral osteoporosis.