Osteoporosis drugs can definitely strengthen bones. However, studies and patient reports over the last four years have uncovered a surprising danger: In some cases, these drugs seem to be breaking bones instead of protecting them.
See also: Can Osteoporosis Drugs Contribute to Bone Fractures?
Now a new study from Sweden has helped put that risk of drug-induced breaks into perspective. The study concluded that the drugs, such as Fosamax, Boniva, Actonel, Atelvia and Reclast, caused one broken femur for every 2,000 people who used them for a year.
In other words, the fractures appear to be so few and far between that the benefit of these drugs outweighs the risk, says Dr. Aurelia Nattiv, director of the UCLA Osteoporosis Center.
"It is encouraging to see this data for patients and physicians," Nattiv said. "It presents one more piece of evidence from a large number of patients that these are good drugs with rare side effects."
Osteoporosis is a disease that makes bones weak and brittle with age. About 10 million Americans already have the condition, according to the National Osteoporosis Foundation. Half of all women and a quarter of all men over the age of 50 will suffer an osteoporotic fracture at some point in their lives. Bone breaks from osteoporosis can happen in any bone, but are most commonly seen in the hips, the spine and the wrist.
Just as the skin constantly makes new cells to replace old ones, bones go through constant turnover. The osteoporosis drugs, known as bisphosphonates, work by slowing down the cells that break down old bone tissue to make way for new bone. This tips the balance toward denser, stronger bones.
And yet, as the drugs are incorporated into bone tissue, they also affect bone structure. It's not clear how this may lead to the specific type of breaks seen with the drugs, known as atypical subtrochanteric fractures.
The drugs have been on the market for 16 years and have quickly become the "gold standard" of osteoporosis treatment, Nattiv says.
The new study, published this month in the New England Journal of Medicine, included every Swedish woman who was at least 55 years old and had a femur (thighbone) fracture in 2008, according to a national registry of patients. Researchers were able to study the X-rays of the women with possible atypical fractures and identified 59 cases.
Of these 59 women, 46 had taken bisphosphonates — out of a total of 83,311 Swedish women who took the drugs that year. That was a fracture rate of less than 0.1%. The 13 other women with atypical fractures did not take the drugs, along with 1.47 million other Swedish women. That worked out to a fracture rate of less than 0.001%.