HealthDay News — First-time users of oral bisphosphonates have an increased risk for inflammatory eye complications compared with nonusers, results of a retrospective cohort study indicate.

First-time users of oral bisphosphonates were 45% more likely to develop uveitis and 51% more likely to develop scleritis compared with never-users, Mahyar Etminan, PharmD, MSc, from the Child and Family Research Institute and the University of British Columbia in Vancouver, Canada, and colleagues reported online in CMAJ, the journal of the Canadian Medical Association.

The number needed to harm was 1,100 for uveitis and 370 for scleritis.

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“The risk of inflammatory ocular adverse events, including scleritis and uveitis, is not highlighted in most package inserts included with oral bisphosphonates,” the researchers wrote. “Patients taking oral bisphosphonates must be familiar with the signs and symptoms of these conditions so that they can seek immediate assessment by an ophthalmologist.”

Clinicians should warn patients about these risks and the need for prompt treatment to prevent further complications, such as cataracts, glaucoma, macular edema and scleral perforation, they suggested.

The analysis involving 934,147 British Columbia residents who had visited an ophthalmologist from 2000 to 2007, including 10,827 first-time users of bisphosphonates. Patients were followed to the first inflammatory ocular adverse event, death, termination of insurance or the end of the study period.

The researchers found that the incidence of uveitis was 29 per 10,000 person-years for bisphosphonate users compared with 20 per 10,000 for nonusers, which resulted in an adjusted relative risk of 1.45 for first-time users.

For scleritis, the incidence was 63 per 10,000 person-years for first-time bisphosphonate users compared with 36 per 10,000 in nonusers, resulting in an adjusted relative risk of 1.51. Results were similar in a propensity score-adjusted analysis.

A separate sensitivity analysis in which treatment with a nonsteriodal antiinflammatory drug was required for the definition of scleritis, the risk remained elevated at 38% among first-time bisphosphonate users compared with nonusers (adjusted RR=1.38, 95% CI: 1.26-1.50).

Study limitations included the use of administrative data without the ability to confirm diagnoses or actual drug intake — only that the conditions had been diagnosed by ophthalmologists and that drugs were dispensed — and the small absolute number of cases among bisphosponate users.

Etmianan M et al. CMAJ. 2012; doi:10.1503/cmaj.111752.