If you were diagnosed with osteoporosis four or five years ago, or if your doctor said your bone density was getting dangerously low and you needed medications, you joined a large group of porous-boned individuals. Osteoporosis affects 10 million Americans; another 34 million have osteopenia (low bone mass). A recent article in the May issue of The New England Journal of Medicine titled “Bisphosphonates for Osteoporosis – Where Do We Go From Here?” discusses the timing and length of indicated therapy.  Apparently  more than 150 million prescriptions have been written between 2005 and 2009, some of them by me…

A quick pharmacologic review: bone is a living tissue that is constantly undergoing resorption (micro drilling) and formation (filling of those micro holes). When the drilling exceeds the filling, bone loss occurs. Over time, the bones can become so porous that they can break or, in more medical terms, fracture. The class of medications called  bisphosphnates such as Fosomax, Actonel, Boniva and Reclast stop the drilling allowing the  filling to continue and thus the bone accumulates lost mass. The bisphosphonates are also incorporated into the newly formed bone and can persist there for years through ongoing cycles of bone resorption and deposition. But with long term use, side effects can occur; these include jaw necrosis and abnormal bone formation. The latter, albeit rare, can cause the long bone in the thigh to loose it’s architectural strength and stability and subsequently break with minimal or no trauma. (This is called an atypical femur fracture.)

The FDA recently reviewed the available long term data on bisphosphonates. Overall  all these medications were effective and increased bone density over a period of three to five  years. Continuation of treatment beyond five years was found to maintain the improved bone density in the  most delicate part of the femur (the femur neck) and improved bone mineral density in the lower vertebrae of the spine (the lumbar area). In patients who were switched to placebo after five years of therapy, bone mineral density in the femoral neck decrease “modestly” during the first two years and then stabilized while the lumbar spine bone density continued to increase.

Ultimately, however, it’s not the numbers in the bone scan that count. The endpoint of therapy has to be a significant decrease in fracture rates…and so far the benefits of fracture protection from continued therapy has been inconsistent. The authors of the article note that pooled data from several studies of patients who have received Bisphosphonates therapy for six years or more shows that fracture rates ranged from 9.3 to 10.6% whereas rates for patients switched to placebo after five years was 8.0 to 8.8%. It seems that at least for some patients stopping therapy after five years won’t compromise their bone gain. They may be a subset of patients, however, that are still at increased risk for fracture, especially older patients with a history of fracture and a bone mineral density that remains in the osteoporotic range. These patients may benefit from continued Bisphosphonate therapy.

Bottom line: if you started one of these bisphosphonate medications to prevent or reverse bone loss and your bone density scan is no longer in the osteoporotic range, or if your bone density improved (although still low) and you have had no fractures, you and your doctor may want to consider discontinuing therapy after five years.