Once-Yearly Zoledronic Acid for Treatment of Postmenopausal Osteoporosis

Although bisphosphonates do inhibit bone resorption in postmenopausal women and lessen the risk of vertebral and hip fractures, as many as half of patients no longer adhere to prescribed oral treatment after 12 months. A single intravenous infusion of zoledronic acid reportedly decreases bone turnover and improves bone mineral density (BMD) for at least a year. In the HORIZON (Health Outcomes and Reduced Incidence with Zoledronic Acid Once Yearly) Pivotal Fracture Trial, an international, randomized, double-blind, placebo-controlled study, postmenopausal women ranging in age from 65 to 89 years were assigned to receive either a 15-minute IV infusion of 5 mg of zoledronic acid or placebo at yearly intervals up to 24 months. All women received a daily supplement of 1000–1500 mg of calcium and 400–1200 IU of vitamin D. Participants had a bone mineral density (BMD) T score of −2.5 or less at the femoral neck or a score of −1.5 or less with 1 or more vertebral fractures. The efficacy analysis included 7736 patients, and the safety analysis, 7714 patients.