Common drugs used to treat the brittle bone disease osteoporosis could make limbs easier to break if used for too long, a new research has suggested.
Scientists found that bisphosphonates improve quantity at the expense of quality. Although the medicines helped preserve bone, over time they appeared to impair its structure.
As a result, it is believed treatment with the drugs may increase the risk of unusual fractures after four or more years.
Bisphosphonates are designed to slow or stop the bone loss that occurs during the body's bone remodeling cycle, or the natural process that involves removal and replacement of bone tissue.
Two separate studies by researchers from Hospital for Special Surgery (HSS) and Columbia University Medical Center revealed data suggesting that long-term suppression of bone remodeling by bisphosphonate treatments may alter the material properties of bone, potentially affecting the bone's mechanical integrity and potentially contributing to the risk of atypical fractures.
"Although bisphosphonates have demonstrated an improvement in bone quantity, little if anything is known about the effects of these drugs on bone quality," said Brian Gladnick, from the Hospital for Special Surgery (HSS).
One team of investigators from Columbia University Medical Center (CUMC) looked at 111 post-menopausal women with osteoporosis, 61 of whom had been taking the drugs for at least four years. The structure of their bones was compared with that of 50 sufferers treated with calcium and vitamin D supplements but not bisphosphonates.
The study found that bisphosphonates improved bone structure early on in treatment, but over time this benefit diminished.
The study has been presented at the 2010 Annual Meeting of the American Academy of Orthopaedic Surgeons (AAOS).