On Wednesday, the U.S. Food and Drug Administration announced that long-term use of bisphosphonates for osteoporosis places patients at a possible risk for atypical thigh bone fractures. The FDA plans to add this warning to its Medication Guide and to the prescribing information for bisphosphonates approved for the treatment of osteoporosis. The warning will not apply to bisphosphonates typically used in the treatment of multiple myeloma or other cancers.

According to Dr. Craig Hofmeister of the Ohio State University Medical Center, myeloma patients taking bisphosphonates for a long time do not need to be concerned about the announcement. “While there is little data to support long-term use (more than 24 infusions in two years) of IV bisphosphonates in myeloma, these atypical femur fractures were less than 1 percent of all fractures in patients with osteoporosis whose use was more than five years.”

Bisphosphonates are a class of drugs that prevent the breakdown of bone. Myeloma patients may receive bisphosphonates to decrease bone pain and prevent the development of bone fractures. Zometa (zoledronic acid) and Aredia (pamidronate) are the two bisphosphonates commonly used in multiple myeloma.

“Currently most myeloma patients treated with bisphosphonates are treated for two years, and then either the interval between treatments is extended or if they have no active disease, it will be stopped by many physicians,” said Dr. David Roodman, Director of the Myeloma Program at the University of Pittsburgh School of Medicine.

Bisphosphonates may also be used to treat osteoporosis because they inhibit the loss of bone mass in patients with this condition. Bisphosphonates have been shown to reduce the rate of osteoporotic fractures.

However, doctors treating patients with atypical thigh bone (femur) fractures observed that many of the patients were concurrently taking bisphosphonates.  Although it is not yet known if bisphosphonates are the cause, the FDA decided to take action because these fractures may be related to use of bisphosphonates for longer than five years.

The FDA had previously announced on March 10 that it would open an investigation into the safety of bisphosphonate use and the occurrence of atypical femur fractures.

After reviewing the data, the FDA recommended the addition of warnings to the products’ prescribing information and better identification and tracking of patients experiencing these atypical fractures. They also plan to conduct additional research to determine if and how bisphosphonates cause these atypical fractures.

The FDA emphasizes that patients taking bisphosphonates for osteoporosis should not stop their medication unless advised to do so by their doctor. However, they recommend that health care professionals reevaluate the need for bisphosphonate treatment for patients who have been treated with bisphosphonates for five or more years.

Dr. Hofmeister did not feel that treatment guidelines for bisphosphonates in multiple myeloma should change based on the FDA warning. “Much more common [in myeloma patients using bisphosphonates] are the risks of renal [kidney] insufficiency (10 percent) and osteonecrosis of the jaw (0.4 to 4 percent).”  He advised that it is more important to check monthly for kidney function and to mandate adequate dental preventive measures.

For more information, please see the FDA press release.