The Toronto Star, April 2, 2012
New Canadian research shows that osteoporosis drugs can increase the risk of serious eye disease.
The findings will no doubt fuel an ongoing debate about whether too many people, particularly post-menopausal women, are being prescribed oral bisphosphonates, said lead author, Dr. Mahyar Etminan, from the University of British Columbia.
The study, published online Monday in the Canadian Medical Association Journal, reveals that the incidence of the inflammatory eye diseases, uveitis and scleritis, is significantly higher for first-time users of these drugs than for non-users.
Oral bisphosphonates are the most commonly prescribed class of drugs used to prevent osteoporosis. They go by such brand names as Fosamax, Actonel and Didrocal and are typically prescribed to post-menopausal women at risk of osteoporosis.
Uveitis is swelling and irritation of the uvea, the middle layer of the eye. Scleritis is an inflammation of the sclera, the white outer wall of the eye. Both conditions can seriously affect vision.
Researchers looked at 934,147 people in British Columbia who had visited an ophthalmologist between 2000 and 2007. Among them were 10,827 first-time users of bisphosphonates and 923,320 non-users.
Researchers found the incidence rate for uveitis in first-time users was 29/10,000 person-years. A person-year is a crude measurement that in this instance could be described as 29 cases of uveitis being found in 10,000 individuals who were followed for one year. For non-users of the drug, researchers found that the incidence rate for the condition was 20/10,000 person-years.
Meantime the incidence rate for scleritis was found to be 63/10,000 for first-time users and 36/10,000 for non-users.
While the findings are statistically significant, Etminan said he doesn’t want to alarm users of the drug because the chance of getting one of these conditions is relatively rare.
Still, clinicians should warn patients of the risk of eye disease, the study says, and anyone on this drug who is experiencing unusual eye pain should go to their doctor and get it checked out.
Oral bisphosphonates have previously been linked to adverse events such as unusual fractures, irregular heartbeat, and esophageal and colon cancer.
Etminan said he did not know how many Canadians take these drugs, but noted there is an ongoing debate about whether they are too often prescribed to people who don’t really need them.
“Unfortunately a lot of women who don’t have a lot of risk factors for osteoporosis, but may have a bit of a thinning of the bone or low bone-mineral density, are also put on the drug,” he said, adding that the drug is most effective in frail, post-menopausal women who have already had a fracture.
A first-time user is defined as someone on their first prescription for a drug. Prescriptions typically last anywhere from 30 to 90 days.
Etminan said it makes more sense to look at first-time users for a study like this since those who have been on the drug longer likely have not and will not experience this side effect. Including them in the study could skew results.