Bisphosphonates, drugs introduced to the market 16 years ago to treat osteoporosis, need labeling to clarify how long patients should take them as data suggests that efficacy decreases while risk increases after some period, panels to the Food and Drug Administration (FDA) voted on Friday.

The FDA does not always officially adopt the recommendation of the panels, but they often do.

If the recommendation is adopted, the labeling would change from the current wording -- “the optimal duration of use has not been determined. All patients on bisphosphonate therapy should have the need for continued therapy re-evaluated on a periodic basis” -- to more specific time frames. 

The FDA’s own report on this issue concluded that long-term bisphosphonates exposure is associated with osteonecrosis of the jaw, atypical subtrochanteric and femoral diaphyseal fractures, and esophageal cancer.

Moreover, benefits appear to plateau after certain years.

The figures the FDA cited for the number of years associated with increased conditions and plateauing benefits range from 3 years to 5 years.

The FDA emphasized that the data shows association, not correlation.  As such, it is “cautious” in interpreting the association results and urged more precise studies to understand the effects of long-term bisphosphonates exposure.

Drugs belonging to the bisphosphonates class include Merck’s Fosmax and Roche’s Boniva.  These drugs have been “highly effective at decreasing the fracture risk associated with osteoporosis,” in the words of the FDA, despite the long-term usage concerns.

Bisphosphonates are mostly taken by by post-menopausal women who have osteoporosis, according to Bloomberg.