Objectives: To determine the efficacy of once-yearly intravenous zoledronic acid (ZOL) 5 mg in reducing risk of clinical vertebral, nonvertebral, and any clinical fractures in elderly osteoporotic postmenopausal women.
Design: A post hoc subgroup analysis of pooled data from the Health Outcome and Reduced Incidence with Zoledronic Acid One Yearly (HORIZON) Pivotal Fracture Trial and the HORIZON Recurrent Fracture Trial.
Setting: Multicenter, randomized, double-blind, placebo-controlled trials.
Participants: Postmenopausal women (aged > or =75) with documented osteoporosis (T-score < or =-2.5 at femoral neck or >/=1 prevalent vertebral or hip fracture) or a recent hip fracture.
Intervention: Patients were randomized to receive an intravenous infusion of ZOL 5 mg (n=1,961) or placebo (n=1,926) at baseline and 12 and 24 months.
Measurements: Primary endpoints were incidence of clinical vertebral and nonvertebral and any clinical fracture after treatment.
Results: At 3 years, incidence of any clinical, clinical vertebral, and nonvertebral fracture were significantly lower in the ZOL group than in the placebo group (10.8% vs 16.6%, 1.1% vs 3.7%, and 9.9% vs 13.7%, respectively) (hazard ratio (HR)=0.65, 95% confidence interval (CI)=0.54-0.78, P<.001; HR=0.34, 95% CI=0.21-0.55, P<.001; and HR=0.73, 95% CI=0.60-0.90, P=.002, respectively). The incidence of hip fracture was lower with ZOL but did not reach statistical significance. The incidence rate of postdose adverse events were higher with ZOL, although the rate of serious adverse events and deaths was comparable between the two groups.
Conclusion: Once-yearly intravenous ZOL 5 mg was associated with a significant reduction in the risk of new clinical fractures (vertebral and nonvertebral) in elderly postmenopausal women with osteroporosis.