The commonly used osteoporosis drug zoledronic acid slows bone loss in postmenopausal osteoporosis patients, but it also boosts levels of a biomarker that inhibits bone formation, according to a study(jcem.endojournals.org) recently published online in the Journal of Clinical Endocrinology & Metabolism.
This X-ray depicts osteoporosis of the hip.
According to the authors, the study evaluated sclerostin serum levels in women with postmenopausal osteoporosis to correlate variations with bone turnover markers after taking zoledronic acid. The women were randomized into two groups, with one group receiving 5 mg of zoledronic acid intravenously and the other receiving a placebo.
The results showed that, in the zoledronic acid group, sclerostin serum levels increased by day two and reached a threefold baseline peak at day seven before decreasing by day 30 and returning near to baseline after 360 days.
Authors said that both serum C-telopeptide of type 1 collagen (CTX) -- a bone resorption marker -- and bone-specific alkaline phosphatase (BSAP) -- a bone formation marker -- were reduced in the treatment group.
"A significant negative correlation was observed between the percentage changes of sclerostin and the variation in BSAP and CTX at all time points in the zoledronic acid group," the authors wrote. "No changes were observed in the placebo group.
"Our data demonstrate that zoledronic acid increases sclerostin serum levels, and that sclerostin could play a role in coupling bone resorption to bone formation."
Lead author Antonino Catalano, M.D., Ph.D., said in a news release(www.endo-society.org) that the study results suggest that zoledronic acid may need to be combined with other treatments to permit new bone formation.
"The data points to an opportunity to increase bone mass by combining zoledronic acid with a drug that suppresses the resulting sclerostin's effect," Catalano said. "An innovative combination therapy using zoledronic acid and selective antibodies to block the sclerostin could simultaneously stop bone loss and encourage new bone formation.
"This is an important avenue for researchers to explore as they develop new osteoporosis treatments."
It's worth noting that in 2010, the FDA notified physicians(www.fda.gov) of a risk of atypical fractures of the femur detected in patients taking bisphosphonates such as zoledronic acid.