Objective: To evaluate the effects of 120 weeks of intermittent cyclical etidronate on the progression of bone loss and fracture incidence and rate in postmenopausal osteoporotic women after 150 weeks of either etidronate or placebo treatment.
Methods: This was an open label followup study of 37 postmenopausal osteoporotic women enrolled from the earlier 150 week study, 17 from the etidronate group and 20 from the placebo group. Treatment cycles were of oral doses of etidronate 400 mg/day for 2 weeks, followed by a 13 week drug-free period for a total of 120 weeks. All patients received a daily supplement of 0.5 g calcium and 400 U vitamin D.
Results: During the earlier 150 week study, mean vertebral bone mineral content increased significantly in the etidronate group by 5.5% (p = 0.013) and decreased by 2.7% (not significant) in the placebo group. After 120 weeks of etidronate treatment in this followup study, patients who had formerly received etidronate experienced an additional 1.4% increase; after 5 years, bone mineral content was 6.9% above the original baseline (p = 0.037). Bone mineral content also increased in the former placebo group during the latter study, up to 5.3% above the original study baseline (not significant). The vertebral fracture rate in the former placebo group decreased significantly, from 103 to 27 per 100 patient-years (p < 0.01), while the fracture rate in the former etidronate group was unchanged (38 and 33 per 100 patient-years).
Conclusion: Five years of etidronate therapy for postmenopausal osteoporosis results in significant increases in vertebral bone mineral content, and the previously observed reduction in vertebral fracture rate in the etidronate group is maintained during at least 5 years of therapy.