Prolonged efficacy of a single dose of the bisphosphonate zoledronic acid.

PURPOSE Bisphosphonates play a central role in the management of bone loss due to a range of disorders, including metastatic bone disease, cancer treatment-induced bone loss, and postmenopausal osteoporosis. With potent bisphosphonates, such as zoledronic acid, it may be possible to maintain efficacy with relatively infrequent administration. EXPERIMENTAL DESIGN Sixty-six patients who were osteopenic at >1 year following curative cancer therapy received a single i.v. 4 mg dose of the bisphosphonate zoledronic acid. Bone mineral density (BMD) was measured using double-beam X-ray absorptiometry scan and the bone resorption marker N-telopeptide of type II collagen was determined using a chemiluminescence ELISA assay. RESULTS The single dose of zoledronic acid induced mean increases in bone BMD at the lumbar spine of 3.1%, 5.2%, and 5.3% and at the total hip of 2.7%, 3.5%, and 4.3% after 12, 24, and 36 months of follow-up, respectively (P < 0.001 at all time points). By 36 months, 84% of patients had achieved increase in BMD at the spine and 90% at the hip. The mean percentage decrease in the bone resorption marker N-telopeptide was approximately 58% at 6 weeks and 42%, 33%, and 31% at 12, 24, and 36 months, respectively (P < 0.001). CONCLUSIONS A single dose of zoledronic acid in patients with low BMD results in a sustained increase in BMD and a corresponding decrease in bone resorption. Very infrequent administration of zoledronic acid may have clinical benefits in terms of convenience, reduced toxicity, improved compliance, and cost.