Similar to vitamin D & statins, bisphosphonates are another one of those therapeutic options that generates quite a bit of controversy, even animosity as each side maneuvers as if it has a moral imperative. So what do we know about medications in general and bisphosphonates in particular. First,
all medications, whether prescription or over-the-counter, have potential side effects. Second,
all dietary supplements, whether herbal, natural, and/or organic, have potential side effects. Third, the
possibility of potential side effects is not the same as the probability of side effects.
The next adage that comes into play is never be the first to prescribe a new medication but never be the last. For many medications, fractionally small side effects don't manifest until a reasonably large number of patients have taken the drug for a long enough period of time. Thus it is with the bisphosphonate class of osteoporosis medications that it's taken a decade or more to gain a better understanding of their potential downside(s). At first, what seemed like a fluke chance of osteonecrosis of the jaw has turned into a steady trickle. The risk is not large but it is real. And for those who are unlucky enough to develop ONJ, it's 100%. Likewise, with atypical femur fractures, what appeared to be a fluke now appears to a small but real trickle.
Adding to this torrent, a
case-control study was published last month in Archives of Internal Medicine in which the
authors concluded that atypical femur fractures were associated bisphosphonate use. No surprise there, at least not anymore. But they also pointed out that the
longer duration of use was associated w/greater risk. However, in the end, the absolute number of these atypical fractures was quite small compared to more typical fractures. In the numbers game known as statistics, it's the difference between relative risk and absolute risk.
How did they arrive at their results? They compared 39 patients with atypical fractures to 438 patients with typical osteoporotic fractures and another 200 patients w/o fractures, everything else being equal, aside from bisphosphonate use. Most of those (82%) who suffered an atypical fracture were found to have used a bisphosphonate compared to just a few (7%) who suffered a typical osteoporotic fracture. Use of said bisphosphonate was associated with almost 50% reduction in typical osteoporotic fracture.
Put another way: the authors calculated 32 atypical femur fractures per million people years of observation compared to 11x that many more typical osteoporotic fractures. And remember that use of bisphosphonates lowers the rate of typical osteoporotic fractures by almost 50%. In absolute numbers, the risk of an atypical femur fracture from bisphosphonate use is fractionally small even when increased by bisphosphonate use compared to the risk of a typical osteoporotic fracture. Sure, if you have an atypical femur fracture, it's 100% for you. But would you rather have worse (greater) odds of sustaining a typical osteoporotic fracture? If you need more information, take a look at
2 more reviews on this topic coming up this Thursday.
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