How Effective Osteoporosis Drug Work?

prescription pills spilled over( — The drug Fosamax are taken by people who have osteoporosis to make their bones stronger. The drug works but experts are wondering why it does not work in the way that they thought it would.

It has been widely believed that bisphosphonates work by targeting and impairing the action of cells known as osteoclasts — and reducing their number. These cells break down bone in a process known as bone resorption.

But in the new study, many postmenopausal women who took Fosamax showed increases in osteoclast numbers compared to women who took a placebo.

The longer the women were on the drug, the more osteoclasts they tended to have. And many also showed evidence of giant and detached osteoclasts, which have not been previously recognized, researcher Robert Weinstein, MD, of the University of Arkansas for Medical Sciences, states.

The study appears in the Jan. 1, 2009, issue of the New England Journal of Medicine.

“The bisphosphonates do work. They are a mainstay of osteoporosis treatment,” he says. “But it is clear that they don’t work the way we thought they did.”

Fosamax vs. Placebo

Weinstein and colleagues from the University of Arkansas and the Central Arkansas Veterans Healthcare System examined 51 bone biopsy specimens obtained following a three-year trial designed to determine the effectiveness of Fosamax for improving bone health.