Denosumab or Zoledronic Acid in Postmenopausal Women With Osteoporosis Previously Treated With Oral Bisphosphonates

Context: Denosumab and zoledronic acid (ZOL) are parenteral treatments for patients with osteoporosis. Objective: The objective of the study was to compare the effect of transitioning from oral bisphosphonates to denosumab or ZOL on bone mineral density (BMD) and bone turnover. Design and Setting: This was an international, multicenter, randomized, double-blind trial. Participants: A total of 643 postmenopausal women with osteoporosis previously treated with oral bisphosphonates participated in the study. Interventions: Subjects were randomized 1:1 to sc denosumab 60 mg every 6 months plus iv placebo once or ZOL 5 mg iv once plus sc placebo every 6 months for 12 months. Main Outcome Measures: Changes in BMD and bone turnover markers were measured. Results: BMD change from baseline at month 12 was significantly greater with denosumab compared with ZOL at the lumbar spine (primary end point; 3.2% vs 1.1%; P < .0001), total hip (1.9% vs 0.6%; P < .0001), femoral neck (1.2% vs −0.1%; P < .0001), and one-third...