The risk-reducing effect of
alendronate on vertebral fractures has been consistently reported. In a 2-year, randomized, double-blind, active drug-controlled (1 microg
alfacalcidol) double-dummy study, we also reported that
alendronate (5.0 mg) had a fracture-reducing effect in Japanese patients with preexisting vertebral fractures. The present report describes the risk-reducing effect of
alendronate (5.0 mg) for 3 years in postmenopausal osteoporotic patients. The 3-year treatment period consisted of the original 2-year double-blind study followed by a 1-year extension. A total of 170 postmenopausal female patients were involved in the third year; 90 received
alendronate and 80 received
alfacalcidol. Both efficacy and safety were analyzed in these 170 patients. Vertebral fracture was determined by quantitative morphometry, and vertebral bone mineral density (BMD) was measured by the DXA method (dual-energy X-ray absorptiometry). The primary efficacy endpoint was the incidence of vertebral fracture, excluding fracture cases that occurred in the first 6 months
after treatment initiation. The cumulative incidence of vertebral fracture at 3 years was 7.8% (7/90) in the
alendronate group and 18.8% (15/80) in the
alfacalcidol group, indicating a significantly reduced risk of fractures in the
alendronate group (relative risk = 0.41, 95% CI = 0.18-0.97). Lumbar spine BMD increased by 9.2% in the
alendronate group (n = 26) and by 1.4% in the
alfacalcidol group (n = 22) at 3 years. The safety profile of
alendronate during 3 years of treatment was similar to that of
alfacalcidol. The present study thus demonstrated that treatment with
alendronate 5.0 mg for 3 years increased vertebral BMD and reduced the risk of vertebral fractures in Japanese, postmenopausal women with
osteoporosis.