In an ironic twist, the Food and Drug Administration warned the millions of people taking drugs to strengthen bones about an increased risk of thigh fractures.
People taking bisphosphonate drugs such as Fosamax may be more likely to suffer the fractures, the agency said. The FDA said it will require labels on the drugs to note the risk, although the government isn't sure why the fractures occur.
The FDA reported that the fractures "may be related to the use of bisphosphonates for longer than five years."
The action followed to recent studies about drugs like Merck's Fosamax and
Roche's Boniva, which are generally used to treat osteoporosis. Osteoporosis is
a disease in which bones become brittle, raising the risk of fracture as we age,
particularly in women.
The studies, reported at the 2010 meeting of the American Academy of Orthopaedic Surgeons, said the drugs may adversely affect bone quality and actually increase the risk of the femur when used for more than four years.
"Although bisphosphonates have demonstrated an improvement in bone quantity, little if anything is known about the effects of these drugs on bone quality," researcher Brian Gladnick, said on behalf of researchers at the Hospital for Special Surgery (HSS) in New York.
Both HSS and the Columbia University Medical Center reported data suggesting that the treatments may alter bone properties in a way that affects the bone's mechanical integrity. That could result in an increase in fractures.
The drugs, heavily marketed in the US and other countries, slow or stop bone loss that occurs as the body replaces bone tissue. The researchers emphasized their preliminary data - based on small samples - shouldn't halt such use. The FDA also said patients should consult their doctors.
Other studies have shown that boomers know little about the disease, which is very common. One in two women over 50 are expected to suffer broken bones in their lives due to osteoporosis, which also affects one in 16 men.
The Columbia research team studied the bone structure of 111 postmenopausal women with primary osteoporosis, including 61 who'd taken the drug for at least four years and 50 who only took calcium and vitamin D supplements. They found improvements in bone integrity early in the treatment, but the gains "diminished" after long-term use.
"In the early treatment period, patients using bisphosphonates experienced improvements in all parameters, including decreased buckling ratio and increased cross-sectional area," said Dr. Melvin Rosenwasser, and orthopaedic surgeon at Columbia. "However, after four years of use, these trends reversed, revealing an association between prolonged therapy and declining cortical bone structural integrity."
The researchers speculated that the results may stem from the way the drugs suppress the body's natural process of producing bone. "Recent research suggests that suppressed bone remodeling from long-term bisphosphonate use might result in brittle bone that is prone to atypical fractures," said Gladnick.
The second, unrelated study by HSS, which was funded in part by the National Institutes of Health, studied 21 older women who'd been treated for femoral fractures. Of those, 112 had taken bisphosphonates for an average of 8.5 years. Only nine had not.
That study analyzed samples of the bone taken from each patient during surgery. Thought it found no differences in the architecture of the bone, the material property of the bone taken from the bisphosphonate group showed inconsistencies associated with reduced strength that could potentially contribute to the fractures.
"Patients who had been treated with bisphosphonates showed a reduction in tissue heterogeneity, specifically with mineral content and crystal size compared with the control group," Gladnick said. "This tells us that there may be some measurable differences in bone quality parameters in patients on long-term bisphosphonate therapy, which might contribute to the development of atypical fractures."
Both teams of researchers said more research is needed before their finding can be applied to treating patients.
"Bisphosphonate use still is a very effective solution that prevents
bone loss in most patients and no one is recommending that physicians avoid
prescribing these," said Rosenwasser. "However, as baby boomers age
and continue to remain active, it is important that we conduct more research and
develop sustainable, safe and effective treatments for osteoporosis."
Editor's Note: This story incorporates material previously reported by RedwoodAge.com