After searching the USC School of Dentistry's electronic medical records database, the study authors found that nine of 208 patients taking Fosamax had active ONJ, a prevalence of about 4 percent. All were patients who had undergone some kind of dental procedure, such as having a tooth removed.
Fosamax (alendronate) is the most widely prescribed oral bisphosphonate and has been the 21st most prescribed drug in the United States since 2006, according to background information in the study.
The jaw complication has been seen in patients taking Fosamax for as little as one year. It seems to occur most frequently after routine tooth extraction, the study authors said.
Although no one is sure why bisphosphonates seem to have this effect only on jaw bones, Sedghizadeh speculated that the drugs may make it easier for bacteria to adhere to bone that is exposed after a tooth extraction.
Previously, experts had thought that ONJ in people taking intravenous bisphosphonates was related to their underlying condition (for example, cancer) than to the actual drug, Liu explained.
The USC School of Dentistry now screens every patient for bisphosphonate use.
"As a school now, we don't have complications any more, we only have referrals," Sedghizadeh said. "We put patients on anti-microbial, anti-fungal rinse one week pre-operatively or post-operatively. If they have been on bisphosphonates six months or a year or longer, then we have a prevention protocol which has been very, very effective."
According to a statement released by Merck & Co., which makes Fosamax, the new study "has material methodological flaws and scientific limitations, making it unreliable as a source for valid scientific conclusions regarding the prevalence of ONJ in patients taking alendronate."
No reports of ONJ have been noted in controlled trials involving more than 17,000 patie
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