September 26, 2003

Combining osteoporosis drugs does not improve bone density

Combining two types of osteoporosis drugs does not improve bone density, according to a study by MGH researchers. Their report in the Sept. 25 issue of The New England Journal of Medicine describes how men with osteoporosis who received both alendronate and parathyroid hormone (PTH) actually had lower bone density at the end of the almost three-year study than did men receiving PTH alone.

Alendronate, one of a type of drugs called bisphosphonates, is FDA approved to treat osteoporosis in men and women and works by slowing the resorption or breakdown of bone. Injections of PTH, a treatment developed through MGH research, increase bone formation and were approved by the FDA in December 2002 to treat osteoporosis. Since the two medications work in complementary fashions, combining both drugs appeared promising.

The 83 study participants were randomly assigned to three groups: one received daily PTH injections, one was treated with alendronate and the third received both therapies. Several measures of bone density were taken during the 30-month study, and although combination therapy improved bone density in the spine more than alendronate alone, neither improved spinal bone density as much as PTH alone. Similar results were seen in other areas measured, and there were no significant differences among the three groups in effects on total body bone density.

"Bone resorption could release growth factors that stimulate bone formation and are necessary to get the full effect of PTH," says Joel Finkelstein, MD, the MGH endocrinologist who led the study. "At this time, we are generally recommending that anyone taking PTH use it by itself and that anti-resorptive therapies be stopped before starting PTH therapy."

The study's coauthors are Robert Neer, MD, senior author; Annmarie Hayes, MSN, RNC, NP; Joy Hunzelman, MSN, NP; Jason Wyland; and Hang Lee, PhD.