The recommended dose is a single intravenous infusion of 5mg zoledronic acid administered once a year. Zoledronic acid, a bisphosphonate, inhibits osteoclast-mediated bone resorption and reduces bone turnover.
The Health Outcomes and Reduced Incidence with Zoledronic Acid Once Yearly (HORIZON) Pivotal Fracture Trial1 investigated the effects of annual infusions of zoledronic acid 5mg on fracture risk during a three-year period.
Patients were randomised to receive a single 15-minute infusion of zoledronic acid 5mg (n=3889) or placebo (n=3876) at baseline, at 12 months and at 24 months; the patients were followed until 36 months.
Treatment with zoledronic acid 5mg reduced the risk of morphometric vertebral fracture by 70 per cent during a three-year period, as compared with placebo (3.3 per cent in the zoledronic acid group versus 10.9 per cent in the placebo group) and reduced the risk of hip fracture by 41 per cent (1.4 per cent in the zoledronic acid group versus 2.5 per cent in the placebo group).
Non-vertebral fractures, clinical fractures, and clinical vertebral fractures were reduced by 25 per cent, 33 per cent and 77 per cent, respectively. In patients aged 75 years and older, zoledronic acid 5mg patients had a 60 per cent reduction in the risk of vertebral fractures compared to placebo patients (p<0.0001).2
Zoledronic acid 5mg was also associated with a significant improvement in bone mineral density and bone metabolism markers. Adverse effects were similar in the two groups, however serious atrial fibrillation occurred more frequently in the zoledronic acid 5mg group than in the placebo group.
1. Black D, Delmas P, Eastell R et al. Once-yearly zoledronic acid for treatment of postmenopausal osteoporosis. N Engl J Med 2007: 356; 1809–22.
2. Aclasta Summary of Product Characteristics, 3 October 2007; Novartis.
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