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Bone drugs’ adverse effect found to be very rare

Posted by medconsumers on May 28, 2010

Remember those scary reports of spontaneous thighbone fractures that occurred in some women who were taking fracture-prevention drugs like Fosamax? The bone breaks for no apparent reason. (In one memorable case, a woman said her thighbone broke while standing in a stalled subway train that lurched suddenly.) Such fractures are described as very rare (0.03%), according to a new analysis of the data generated by three large trials. These are the same clinical trials that proved bone drugs like Fosamax and Zometa are more effective than no treatment (placebo) in reducing hip fracture—the most serious complication of osteoporosis. Now the results of these trials were searched solely for the rate of spontaneous thighbone fracture.

It’s a relief to know that this is “a very rare” side effect of osteoporosis drugs. But looking at these trial results again reminds me that their hip fracture prevention benefit is also pretty rare. The first to win FDA approval was Fosamax (generic name: alendronate), produced by Merck. After three years, only 1% fewer drug-treated women suffered a hip fracture, compared to untreated women. The drugs’ effectiveness looks much better when the company-sponsored researchers throw in fractures in other sites—spine, wrist, and forearm. In one osteoporosis research sleight of hand that’s always bothered me, it is common to count a reduction in spinal fractures that are symptomless and can be seen only on X-ray.

But I digress. Back to the spontaneous thighbone fractures and how we now know they are very rare. The three major trials that provided the data for this conclusion had a combined total of 14,195 women randomly assigned to take either a placebo or a bone drug (Fosamax in two trials, Zometa in one). Keep in mind that most of what are called hip fractures are actually breaks in the “neck” of the femur, or thighbone, where it meets the pelvis in the ball and socket joint.

So here’s final count: Of the 284 women who had hip or femur fractures, only 10 had what’s called atypical thighbone fractures. It’s interesting to note how few hip or femur fractures—atypical or not—occurred, considering that the 14,195 study participants were considered to be at high risk for fracture and between the ages of 65 and 80 years when they entered the study. Could it be that this isn’t the biggest health threat we face in old age? Or could it be that the study participants weren’t followed long enough?

This analysis appeared in The New England Journal of Medicine and was funded by Merk and Novartis (maker of Zometa). How long can people safely take this drug is not answered by this analysis. It’s a question that lingers over all bone drugs called bisphosphonates (other brand names: Boniva, Actonel, Reclast). The authors of this analysis conclude that the risk of spontanous thighbone fracture remains rare “even among women treated with bisphosphonates for as long as ten years.” Buried deep in this paper, however, is the fact that few women were followed this long. The majority were followed only three to four years. Women on long-term bisphosphonate therapy are advised to report thighbone pain immediately to their doctors as this was the telling symptom that preceded a spontaneous fracture.

For more information

To determine whether you can benefit from Fosamax or any other bisphophonate drug, see this chart from the Cochrane Collaboration, which is based on the results of the above-mentioned three clinical trials. You will see that women who have been diagnosed with low bone density or who have broken bones in their spines are more likely to benefit than those whose bone density is near normal (osteopenia) or who do not have spinal fractures. click here

Update added April 2011: Read the latest article called “Bisphosphonate drugs—more harm than good?” click here

Visit the Web site of Susan Ott, MD, an expert in bone physiology at the University of Washington, Seattle. Everything from osteoporosis prevention to summaries of the latest bisphosphonate studies.

For background on how osteoporosis became a much-feared disease, read this 2009 article for the American Journal of Nursing, The Marketing of Osteoporosis.

Osteonecrosis of the jaw, another rare side effect of bisphosphonate drugs, was not addressed in the new analysis. For more information, click here.

Maryann Napoli, Center for Medical Consumers(c)

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