Vitamin K Doesn't Reduce Bleeding in Warfarin Patients

But single dose in overanticoagulated patients may help lower international normalized ratio
By Rick Ansorge
HealthDay Reporter

TUESDAY, Mar. 3 (HealthDay News) -- In patients receiving warfarin, vitamin K does not reduce bleeding, according to study findings published in the Mar. 3 issue of the Annals of Internal Medicine.

Mark Crowther, M.D., of McMaster University in Hamilton, Ontario, Canada, and colleagues conducted a randomized controlled trial in which 347 patients received a single dose of 1.25 mg of oral vitamin K and 365 patients received matching placebo. All patients had an international normalized ratio (INR) of 4.5-10.0 and were instructed to withhold warfarin for one day before receiving either vitamin K or placebo.

After 90 days, the researchers found that similar percentages of patients in the vitamin K and placebo groups experienced at least one bleeding complication (15.8 percent versus 16.3 percent) or thromboembolism (1.1 percent versus 0.8 percent). INRs measured one day after treatment revealed decreases of 1.4 and 2.8 in the placebo and vitamin K groups, respectively.

"Despite this negative primary finding, we detected no between-group differences in the frequency of stroke or thromboembolism, suggesting that vitamin K is at least safe, and confirmed previous observations that a low dose of oral vitamin K more rapidly returns the INR toward the therapeutic range," the authors write.

Crowther disclosed receiving consultancy fees from Anton Pharmaceuticals.

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