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Patients who over-respond to warfarin are often treated with vitamin K, which quickly lowers INR. Investigators at 14 anticoagulation clinics in Canada, the U.S., and Italy conducted a randomized, placebo-controlled trial to find out whether low-dose oral vitamin K (1.25 mg) would reduce bleeding events in patients with INRs between 4.5 and 10.0 on warfarin. Patient characteristics did not differ significantly between the two groups, and all patients were treated with vitamin K (n=355) or placebo (n=369), as allocated.
Ninety days after enrollment, 56 (15.8%) of the vitamin K recipients and 60 (16.3%) of the placebo recipients had had a bleeding event; such events occurred within 7 days in 28 (7.9%) and 34 (9.2%) patients in the vitamin K an…