Bisphosphonates May be Less Effective in Preventing Fractures after Five Years

A new study published in the New England Journal of Medicine is raising new concerns about the efficacy of long-term bisphosphonate therapy.  The analysis, which was conducted by the U.S.  Food & Drug Administration (FDA), found that after about 3 to five years of use, bisphosphonates like Fosamax do little, if anything, to reduce the risk of fractures from osteoporosis.

In conducting the bisphosphonate analysis, the FDA looked at two previously released studies that involved more than 2,400 post-menopausal women. One tracked Fosamax users for up to 10 years, while the other followed users of Reclast for six years.  While women taking either Fosamax or Reclast experienced fewer fractures during the first three years of use compared to those taking a placebo, the gap narrowed after five and six years.

The report didn't include guidance about long-term use, stating that an individual's risk should be discussed with their doctor.  However, the agency did say that women at low risk for fracture or with a bone density near normal may be good candidates to stop therapy after three to five years, while older patients at higher fracture risk and bone density “in the osteoporotic range” may benefit from continued therapy.

An accompanying editorial asserted that women most likely to benefit from long-term bisphosphonate therapy  are those who continue to have very low bone density, as measured by something called a “T score” that is lower than minus 2.5 after three to five years of treatment. Those with a history of spinal fracture or with an existing fracture also are most likely to benefit from long-term use of the drugs, the researchers concluded.