One annual infusion of zoledronic acid (Reclast) significantly reduces fracture risk in postmenopausal women with osteoporosis, according to results of a major trial.

An international group of investigators, led by Dennis Black, MD, of the University of California, San Francisco, randomized more than 7,700 osteoporotic women, median age 73, to annual 15-minute IV infusions of zoledronic acid (5 mg) or placebo.

During the three-year study period, zoledronic acid reduced the risk of vertebral fracture by 70% and the risk of hip fracture by 41%, compared with placebo. Zoledronic acid—which stops excessive bone breakdown and rebalances the remodeling process—was also associated with a significant improvement in bone mineral density and bone metabolism markers. The drug was approved earlier this year for Paget’s disease and will be submitted for review for treating osteoporosis, according to Novartis, the manufacturer.

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Adverse events, including changes in renal function, were relatively mild and occurred with similar frequency in the two study groups. However, serious atrial fibrillation occurred more frequently in the zoledronic acid group than in the placebo group—50 vs. 20 patients.

In conclusion, say the authors, “Given the relatively poor adherence to oral bisphosphonate therapy in clinical practice, annual infusion of zoledronic acid may provide a promising approach to reducing fracture risk” (N Engl J Med. 2007; 356:1809-1822).