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Long-term use of bisphosphonates may increase risk of atypical fractures: studies
  by Lianne Dane
Preliminary research presented Wednesday at the annual meeting of the American Academy of Orthopaedic Surgeons showed that bisphosphonate drugs may adversely affect bone quality and increase the risk of atypical femur fractures in postmenopausal women with osteoporosis when used for four or more years, compared with women not treated with the drugs.
Investigators in the first study evaluated the bone structure of 111 postmenopausal women with primary osteoporosis, including 61 patients who took bisphosphonates for a minimum of four years and 50 patients who did not take such products. Findings indicated that "in the early treatment period, patients using bisphosphonates experienced improvements in all parameters, including decreased buckling ratio and increased cross-sectional area," but after four years "these trends reversed, revealing an association between prolonged therapy and declining cortical bone structural integrity," commented researcher Melvin Rosenwasser.
In a separate study, researchers evaluated the bone composition of 21 patients, including 12 patients who had taken bisphosphonate drugs for an average of 8.5 years and nine who had not taken the drugs. Investigator Brian Gladnick noted that "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." He explained that "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."
Rosenwasser remarked that "bisphosphonate use still is a very effective solution that prevents bone loss in most patients." The investigators added that more research is needed to determine the efficacy of long-term clinical use of bisphosphonates for the treatment of osteoporosis, and that the results of their studies will not likely affect clinical practice in the near future.
Separately, the FDA said in a safety announcement that its review of the long-term use of oral bisphosphonates is ongoing. In June 2008, the agency requested information from all bisphosphonate drug manufacturers regarding the potential increased risk of atypical subtrochanteric femur fractures in women with osteoporosis being treated with the products. "At this point, the data...have not shown a clear connection between bisphosphonate use and a risk" of these fractures, the FDA stated.
Bisphosphonates, such as Merck & Co.'s Fosamax (alendronate), Roche and GlaxoSmithKline's Boniva (ibandronate), Novartis' Reclast (zoledronic acid), plus sanofi-aventis and Procter & Gamble's Actonel (risedronate), have combined annual sales in the US estimated at more than $3.5 billion.
Reference Articles
Quantity vs. quality: long-term use of bone-building osteoporosis drugs may affect quality and structural integrity of bone - (AAOS)
FDA to investigate possible osteoporosis drug-femur fracture link ABC News report - (ABC News)
FDA Drug Safety Communication: Ongoing safety review of oral bisphosphonates and atypical subtrochanteric femur fractures - (FDA)
Do osteoporosis drugs boost bone quantity at the expense of quality? - (The Guardian)
Common osteoporosis drugs 'could make limbs weaker if used for too long' - (The Telegraph)
Long-term use of osteoporosis drugs linked to hip breaks - (USA Today)
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