Osteoporosis drugs linked to eye infections in some first time users: study

TORONTO – First time users of oral osteoporosis drugs may be at an increased risk of developing serious eye conditions, a new study suggests.

Doctors should alert new users of bisphosphonate drugs to the warning signs of the infections, which can lead to permanent eye damage if they are not properly treated, it says.

The work, by researchers from the University of British Columbia, is published in this week’s issue of The Canadian Medical Association Journal.

Lead author Dr. Mahyar Etminan said that while the events seem to be rare, the period shortly after a person starts taking these drugs is a time to be on the lookout for uveitis and scleritis.

“I think the message here is people who are just starting on these drugs or new users may be at an elevated risk than somebody who’s been on them for years,” said Etminan, a drug safety researcher with the department of medicine at the University of British Columbia and the Therapeutic Evaluation Unit, part of the Child and Family Research Institute of British Columbia.

Oral bisphosphonates are the most frequently prescribed class of drugs for prevention of osteoporosis; about five million prescriptions for these drugs are filled every year in Canada. Bisphosphonates can also be given by injection, but this study did not look at people who receive the drug that way.

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Etminan said there have been numerous case reports and case studies – journal reports describing the experiences of a group of patients – suggesting a possible link between the drugs and these eye conditions in new bisphosphonate users. But the only large study done found few cases and no association.

In this study, he and his co-authors looked at more than 934,000 B.C. residents who went to ophthalmologists from 2000 to 2007. They identified among them the people who had been recently prescribed oral bisphosphonates and compared the rates of uveitis and scleritis among the new users and people who had not recently started oral bisphosphonate therapy.

Uveitis was seen at a rate of 29 cases per 10,000 person years in new users of oral bisphosphonates, versus 20 per 10,000 in people who hadn’t recently started on the drug.

For scleritis, the risk appeared to be higher. There were 63 cases of scleritis per 10,000 person years in new users versus 36 per 10,000 in people who were not new users.

Put another way, among new users of the drugs you would expect to see one excess case of uveitis for every 1,100 new prescriptions, and one additional case of scleritis for every 370 new users.

Uveitis is the swelling and irritation of the uvea, the middle layer of the eye while scleritis is an inflammation of the sclera, the white outer wall of the eye.

The inflammation caused by one form of uveitis – posterior uveitis – can last for months and even years and may cause permanent vision damage, even with treatment. If untreated, scleritis can lead to perforation of the eyeball, which can result in vision loss.

Etminan said the conditions are generally intensely painful, and can develop within days of the start of bisphosphonate treatment. He said the study design doesn’t allow the authors to say when a new user’s risk goes back to normal, though he suggested someone who has been using the drugs for six months is probably less likely to develop the conditions.

The study points out that these possible adverse reactions aren’t typically noted on the warning labels, but people who are starting these drugs need to know the symptoms and seek help if they develop.