NEW YORK (Reuters Health) – Novel antithrombotics such as dabigatran or rivaroxaban are associated, in some instances, with a decreased risk of intraocular hemorrhage compared with traditional anticoagulant therapy, researchers suggest.
Dr. Brian VanderBeek of the University of Pennsylvania, in Philadelphia, and colleagues retrospectively conducted two separate analyses of intraocular bleeding risk using data from a large U.S. insurance claims database.
Patients prescribed dabigatran or rivaroxaban from January 2010 through September 2015 were compared with those prescribed warfarin. Similarly, patients started on prasugrel were compared with those started on clopidogrel.
People with a previous diagnosis of intraocular hemorrhage were excluded.
“We used a real-world population – people who are often older and sicker than those seen in clinical trials and are more representative of how medications are typically used in practice,” Dr. VanderBeek told Reuters Health.
“We were able to specifically control for eye conditions that predispose patients to having intraocular bleeds including diabetic retinopathy, age-related macular degeneration and retinal vein occlusions . . . and for other medications that are known to mitigate or inhibit the effects of the study medications,” he said by email.
As reported in JAMA Ophthalmology, online December 14, the first analysis compared 146,137 patients taking warfarin (mean age, 69.8; about 53% women) with 64,291 patients (mean age, 67.6; about 50% women) taking dabigatran or rivaroxaban.
A 25% lower hazard for developing an intraocular hemorrhage with dabigatran or rivaroxaban was seen at 365 days, but not at 90 days.
The second analysis compared 103,796 patients taking clopidogrel (mean age, 68; 36% women) with 8,386 patients taking prasugrel (mean age, 61; about 25% women). No significantly increased hazard for developing an intraocular hemorrhage with prasugrel was seen at either 90 or 365 days.
“These results suggest a decreased risk of intraocular hemorrhage associated with novel direct thrombin inhibitors and direct factor Xa inhibitors, but no difference for P2Y12 inhibitors compared with traditional vitamin K anticoagulation and antiplatelet therapy, respectively,” the authors conclude.
Dr. VanderBeek said, “The main caveat to our study was that we excluded anyone who had a previous history of a bleed. This was done to try and make the groups as equal for comparison as possible, but the converse to this is that our results may not generalize to people who have had a previous intraocular bleed.”
“Additionally,” he noted, “we did not have enough data to study all of the novel anticoagulants, including apixaban and edoxaban tosylate.”
Dr. Daniel Caldeira of the University of Lisbon, Portugal, author of a related editorial, told Reuters Health the findings are “clinically relevant because some of these novel drugs have shown an increased antithrombotic efficacy in randomized controlled trials, and this is often accompanied by an increase in hemorrhage risk.”
“The comparative safety of these novel drugs in ‘real-world’ conditions, without the selection bias of controlled trials, (provides) reassurance for their use,” he said by email, “particularly regarding an outcome that may lead to severe disability, such as vision loss.”
Dr. Caldeira also emphasized that the study is observational and, as Dr. VanderBeek also noted, other oral anticoagulants were not included in the comparisons.
Dr. Mark Link, director of cardiac electrophysiology at UT Southwestern in Dallas, told Reuters Health the lack of difference in bleeding risk between warfarin and the direct anticoagulants at 90 days “was likely due to the decreased number of events at 90 days, as the proportional risk was similar – 75% compared to warfarin.”
“This result is not surprising, as in most trials of warfarin compared to the direct anticoagulants the risk of bleeding was lower with the direct anticoagulants, with the possible exception of gastrointestinal bleeding,” he said by email.
“Importantly,” he added, “in these previous trials the risk of intracranial bleeding was lower with the direct anticoagulants.”
“In the second analysis comparing clopidogrel, a first-generation P2Y12 inhibitor, to prasugrel, there was no difference in intraocular bleed,” he continued. “This was perhaps a bit surprising because the clinical trials generally showed an increased risk of bleeding with prasugrel.”
“The clinical implications of (the findings are) that they again demonstrate lower bleeding rates with the newer anticoagulants and offer more support for these drugs,” said Dr. Link, who was not involved in the study. “I don’t think it changes the clinical picture for the antiplatelet agents.”
SOURCES: http://bit.ly/2AVbhsT and http://bit.ly/2CWf1vx
JAMA Ophthalmol 2017.
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