Research links bisphosphonates to rare, but serious, jaw osteonecrosis -- prevention seen as best “cure.”

The drugs you are taking to prevent or treat osteoporosis may be linked to an uncommon jaw disease called osteonecrosis. The reports first surfaced in 2003 when oral surgeons noticed that people taking these drugs -- called bisphosphonates -- were not healing well after they underwent jaw surgery.

How can drugs designed to prevent brittle bones actually cause the jaw bone to rot? How common is this side effect? Are you at risk? What should you do if you are?

Oral bisphosphonates are widely prescribed for people with, or at-risk of developing, the brittle bone disease osteoporosis. They are also used in higher doses to treat certain types of cancer. Cancer patients receive the drugs intravenously to treat cancers that have spread to the bone and cause pain.

Widely Prescribed

Any way you look at it, a lot of people are taking -- and need to take -- these medications. According to the American Association of Endodontists, more than 30 million Americans take these drugs each year to treat cancer, osteoporosis, and other bone diseases including Paget’s disease (a condition that causes abnormal bone growth).

Oral bisphosphonates include alendronate (Fosamax), ibandronate (Boniva), and risedronate (Actonel); intravenous forms include pamidronate disodium (Aredia), zolendronic acid (Zometa), and clodronate (Bonefos).

When the link between these drugs and osteonecrosis was first noticed, it occurred primarily among people taking these drugs intravenously to treat cancer. The majority of cases followed a major dental procedure such as a tooth extraction, but some occurred spontaneously.

Now many dentists are noticing the condition among people who take these drugs in pill form to stave off osteoporosis. As a result, the FDA has called on the manufacturers of all bisphosphonates to include a warning on their labeling about the risk of osteonecrosis of the jaw. In addition, the American Society of Bone and Mineral Research is in the process of convening a multidisciplinary, international task force to examine this issue.

Researchers are unsure exactly why these drugs may cause the condition, but some postulate that while bisphosphonates increase bone density in the short run, they may impair new bone formation in the long term. This may reduce the jawbone’s capacity to heal after traumas such as dental extractions or implants.

Exactly how often it occurs is also unknown. A study in Current Opinions in Orthopaedics found that one to 10 percent of people with advanced cancer who are on IV bisphosphonate therapy develop jaw osteonecrosis. The number is much lower in people who take these drugs by mouth for osteoporosis.

An Ounce of Prevention

One thing is known, however: Experts agree that the best way to treat jaw osteonecrosis is to prevent it from occurring in the first place. To that end, the American Dental Association recently published guidelines to help the millions of people taking these medications cut their risk of developing this serious condition.

For starters, any person taking these drugs should discuss the risks with their dentist before undergoing procedures that involve the jawbone. Guidelines also recommend that you:

• Get a dental exam before starting therapy
• Consider having major dental work done before starting bisphosphonate treatment
• Practice good oral care, including regular brushing and flossing

If your doctor suspects jaw osteonecrosis, he or she may use x-rays, or test for infection. Treatments can include antibiotics, oral rinses, and removable mouth appliances. In some cases, minor dental work may be necessary to remove injured tissue and reduce sharp edges of damaged bone. Surgery typically makes the condition worse.

What’s more, stopping therapy once this condition has developed does little good because medications are metabolized slowly and therefore remain in the bone for many years.

The View from Duke

Thomas Weber, MD, Assistant Professor of Medicine at Duke University School of Medicine, says, "Don’t panic. Jaw osteonecrosis is a serious condition, but it’s rare. It is primarily seen in patients taking IV forms of bisphosphonates to treat cancer, but the observed rate is less than one per 100,000 patient-years in people who take alendronate for osteoporosis. There are fewer reported cases with the other bisphosphonates, but they have not been around as long as alendronate.

"To be on the safe side, get a dental evaluation to make sure there is nothing that needs to be taken care of imminently before beginning bisphosphonate therapy. If you are already taking bisphosphonates, let your dentist know, make sure to get routine dental care, and practice good dental and periodontal hygiene.

"I counsel every patient in my practice who is on an oral or IV bisphosphonate on the known risks and benefits of the therapy. For the vast majority of patients, the benefits of taking bisphosphonates to prevent fractures will outweigh the potential risks."