How Osteoporosis Drugs Work
November 17, 2012
If you’re one of the 44 million Americans at risk for osteoporosis—a disease in which bones become weak and are more likely to break—you may be taking bisphosphonates. This class of drugs has been successfully used since 1995 to slow or inhibit the loss of bone mass. Doctors commonly prescribe such brand-name drugs as Actonel, Atelvia, Boniva, and Fosamax (as well as a number of generic products) for osteoporosis. In fact, more than 150 million prescriptions were dispensed to patients between 2005 and 2009.
Bones go through a continual process of remodeling, in the form of bone resorption (disintegration) and bone formation. Bone loss related to osteoporosis occurs when resorption is greater than formation. Bisphosphonates decrease bone resorption, thereby slowing bone loss.
During treatment, bisphosphonates become part of the newly formed bone and can stay there for years, through many cycles of resorption and formation. Patients continue to be exposed to the effects of the drug even long after they’ve stopped taking it.
According to Whitaker, the studies that FDA considered focused on patients who had been using bisphosphonates for at least three years and as many as 10. They looked at outcomes related both to bone mineral density and bone fractures.
“Bisphosphonates have been proven very effective in protecting against bone fractures in clinical trials lasting three to four years,” says Whitaker. But it’s still unknown whether the benefit lasts longer than that in decreasing the risk of fractures.
Bisphosphonate labels have carried a safety warning about severe jaw bone decay (osteonecrosis of the jaw) since 2002. In October 2010, FDA warned patients and health care professionals about the increased risk of unusual thigh bone fractures and directed manufacturers to include the warning in the safety labels and medication guides that come with prescription medications. FDA continues to evaluate the possible association of bisphosphonates with esophageal cancer. These associations would suggest that health care professionals may want to reconsider how long patients should continue taking the drugs.