Confusing reports on bisphosphonates: Fosamax, Actonel, Boniva, and Reclast

One may be puzzled or even confused by the reports that taking bisphosphonates (the drug treating osteoporosis and reducing the incidence of bone fractures) can cause hip fracture, the very condition that the drug aims to prevent.

FDA issued an Safety Labeling change on 10/13/10 saying “atypical” fractures of the thigh bone (femur) have been observed in patients who have been taking a bisphosphonate for many years.  The term ‘atypical’ is used as these fractures tend to happen in an unusual site (anywhere in the femoral shaft from just below the lesser trochanter to above the supracondylar flare) and it often happens with “low-energy, or low trauma”; i.e. no or a minor accident that doesn’t amount to anything can cause fractures.

The ‘atypical’ fractures are very uncommon, accounting for less than 1% of all hip and femur fractures overall.  But, the true incidence of atypical fractures is unknown for it may be under recognized and under reported.

FDA emphasized that causality has not been established; i.e. bisphosphonates may or may not cause these atypical fractures.  The optimal duration of bisphosphonate use for osteoporosis is unknown.  Since atypical fractures appear to increase along with the longer duration of use, a periodic reevaluation (risk/benefit assessment on an individual case) of continued use is advisable, especially after 5 years of use (I went to a conference sponsored by Harvard Medical School in October 2011 and they stop using bisphosphonate after 5 years.)  One study suggested the benefit of a bisphosphonate may linger even after it is stopped after 5 years of use.

Bisphosphonates used in the States:

Fosamax (alendronate), Actonel (risedronate), Boniva (ibandronate), and Reclast (zoledronic acid)

If one takes bisphosphonates for conditions (such as Paget’s disease of bones; Reclast is used to treat hypercalcemia of malignancy) other than osteoporosis, then it is not subjected to this Safety Labeling change.

If we know the true incidence of atypical fractures while taking bisphosphonates, then thing would be much easier.  We do have more precise numbers of complications of blood transfusions.  1-4 in 100 may have febrile (fever) reaction; i.e. 1-4%; 1 in 103,000 may contract hepatitis C; 1 in 200,000 may contract hepatitis B, and 1 in 490,000 may contract HIV.