Patients and doctors have been warned about a serious side effect associated with a group of drugs commonly prescribed for the treatment of osteoporosis, after the initiation of a second review of their safety.
There is mounting concern at the increased incidence of death of bone in the jaw (osteonecrosis) in patients treated with bisphosphonates, a class of drugs used to combat bone thinning.
Bisphosphonates are also used to treat certain cancers, such as multiple myeloma and bone secondaries in women with breast cancer.
The Irish Medicines Board (IMB) yesterday issued its second warning in 18 months about the drug.
"Osteonecrosis of the jaw continues to be reported as a suspected adverse drug reaction associated with bisphosphonates and the number of reports appear to be increasing, particularly for the most potent bisphosphonates," it said in a statement.
It has emerged that those patients treated with an intravenous version of the drug are most at risk of the extremely painful and irreversible destruction of the mandible (jaw bone).
However, this serious side effect has also been identified in patients taking bisphosphonates orally.
An initial review carried out by the European scientific committee responsible for medicines' safety concluded that the risk of osteonecrosis of the jaw was linked to the potency of the bisphosphonates, their use in the treatment of people with cancer, and intravenous administration.
Although the condition has been intensively studied since it first came to light in 2003-2004, the reason why it happens has yet to be identified.
Doctors and dentists have also been unable to unravel the disease process linking the drug with the destruction of bone.
Initially, dentists and oral surgeons attempted to treat the condition by cutting away the diseased area of bone. This, however, this made the situation worse.
It now appears the best treatment is with antibiotic rinses, such as chlorhexidine.
A number of risk factors make it more likely that a patient taking bisphosphonates will develop jawbone destruction.
These include: having cancer; being treated with steroids, chemotherapy or radiotherapy; and malnutrition. Women and older people are also at increased risk.
Asked to comment on the warning, Dr Joan Gilvarry, director of human medicines with the IMB, said: "While this issue has been previously reviewed by the Irish Medical Board and across the European Union, adverse reactions continue to be reported.
"The IMB in conjunction with the European Medicines Agency is now conducting a second review and I would urge all healthcare professionals to report any suspected cases of osteonecrosis to facilitate monitoring of this significant safety concern."
Dr Peter Cowan, director of dental affairs with the Royal College of Surgeons in Ireland, told The Irish Times that dentists now advise that patients about to embark on bisphosphonate treatment complete dental surgery first.
Patients on oral bisphosphonates are usually asked to stop the drug for a minimum of three months prior to oral surgery.
The brand names of bisphosphonates which are available on the market here include Fosamax, Osteomel, Bonefos, Didronel, Bonviva, Aredia, Actonel, Zometa and Aclasta.