(RxWiki News) They're designed to strengthen bones. This class of drugs known as bisphosphorates is also prescribed to cancer patients to treat excessive calcium in the blood.
These drugs can actually increase the risks of unusual bone fractures.
Bisphosphonates seemed to be linked to an increased risk of unusual fractures of the femur - the thigh bone.
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Researchers in Switzerland analyzed data on 477 patients over the age of 50 who had been hospitalized for a break in the unusual (atypical) thigh shaft bone. A group 200 healthy individuals who had a femur fracture were also identified.
The investigators found 39 patients who had the atypical fractures and 238 who had a more common type of femoral fracture.
Of those who had the atypical fracture, most - 82.1 percent - had received bisphosphonates, compared to 28 patients (6.4 percent) who had common breaks.
And while it looks like this class of drug increases risks of unusual fractures, the drugs were also associated with 47 percent decrease risk of classic fracture.
"Current evidence suggests that there is an association between bisphosphonate therapy and atypical femoral fractures, but the extent of this risk remains unclear," according to Raphael P. H. Meier, MD, and colleagues from University Hospitals of Geneva and Faculty of Medicine, Geneva, Switzerland.
The length of treatment had an impact on the risk factors of developing an atypical vs. a classic fracture. Individuals who had been treated with bisphosphonates had the following risks of an atypical fracture:
- Less than two years, 35.1 percent
- Two-five years, 47 percent
- Five-nine years, 117.1 percent
- More than nine years, 175.7 percent
Adam Brufsky, MD, PhD, professor of medicine at the University of Pittsburgh School of Medicine, told dailyRx, "The low incidence of atypical fractures is important, especially with prolonged use of these drugs. The benefits, however are substantial in the end; we will likely use these drugs for less time," Dr. Brufsky said.
The authors conclude that while there appears to be an association between treatment and atypical fractures, "the absolute benefit to risk ratio of bisphosphonate use remains positive."
This research was published May 21, 2012 Online First by Archives of Internal Medicine, a JAMA Network publication.
One of the authors reported financial relationships with Servier, Novartis, Eli Lilly, Amgen, Roche, Nycomed, Merck Sharp and Dohme, Alken and Danone.