(HealthDay News) – First-time users of oral bisphosphonates have an increased risk of both uveitis and scleritis compared with nonusers, according to a study published online April 2 in CMAJ, the journal of the Canadian Medical Association.

To investigate the risk of uveitis and scleritis among patients taking oral bisphosphonates, Mahyar Etminan, PharmD, of the Child and Family Research Institute in Vancouver, Canada, and colleagues conducted a retrospective cohort study involving 934,147 people who had visited an ophthalmologist from 2000–2007, including 10,827 first-time users of bisphosphonates.

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. The number needed to harm was 1,100 for uveitis and 370 for scleritis. The results were similar in a propensity score-adjusted analysis.

“The risk of inflammatory ocular adverse events, including scleritis and uveitis, is not highlighted in most package inserts included with oral bisphosphonates,” the authors write. “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.”

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