MedWire News: Taking a vitamin K dietary supplement improves the stability of oral anticoagulation therapy with vitamin K antagonists, which could reduce bleeding and thrombotic events, report Dutch scientists.

One of the disadvantages of oral anticoagulant treatment with vitamin K antagonists is unstable anticoagulant control, with the intensity of anticoagulation within the target range just 60% of the time. One of the reasons for this is a fluctuating intake of vitamin K.

Research suggests that patients with a low dietary intake of vitamin K have less stable anticoagulant control than those with a high intake. Felix van der Meer and colleagues from Leiden University Medical Center investigated by randomly assigning 200 patients receiving the vitamin K antagonist phenprocoumon to receive either 100 µg vitamin K once daily or placebo.

Over 24 weeks of treatment, patients supplemented with vitamin K spent 89.5% of the time within the therapeutic range, compared with 85.5% among patients given placebo, at an adjusted difference of 3.6%, the team reports in the Journal of Thrombosis and Haemostasis.

Patients in the vitamin K group spent 2.1% of the time below the therapeutic range, compared with 3.1% of the time for placebo patients, at an adjusted difference of -0.7%. The time spent above the therapeutic range was 8.5% in the vitamin K group and 11.4% in the placebo group, at an adjusted difference of -2.9%. The relative risk for maximal stability with vitamin K versus placebo was 1.8.

"Our results show that supplementation with a low dose of oral vitamin K contributes to improved anticoagulant stability," the team writes. "Further research on the optimal dosage of vitamin K supplementation in various patients groups is necessary to optimize anticoagulant control."

Free abstract