Vitamin K supplementation improves stability of anticoagulation

General

Clinical Question:
Can vitamin K supplementation help achieve stable control of anticoagulation in adults taking warfarin?

Bottom Line:
Vitamin K supplementation can help achieve control of anticoagulation in adults with unexplained instability of response to warfarin. This may be a welcome relief to frustrated patients, clinicians, and staff. (LOE = 1b)

Reference:
Sconce E, Avery P, Wynne H, Kamali F. Vitamin K supplementation can improve stability of anticoagulation for patients with unexplained variability in response to warfarin. Blood 2007;109(6):2419-23.  [PMID:17110451]

Study Design:
Randomized controlled trial (double-blinded)

Funding:
Unknown/not stated

Allocation:
Concealed

Setting:
Outpatient (specialty)

Synopsis:
Anticoagulation that is difficult to control in adults taking warfarin may be due to an irregular intake of foods that contain vitamin K. These investigators identified 70 warfarin-treated adults with unstable anticoagulation, defined as having a standard deviation of INR values greater than 0.5 (indicating a wide swing in values) and at least 3 warfarin dose changes in the previous 6 months. Eligible patients randomly received vitamin K (150 ug daily) or matched placebo in a double-blind fashion (concealed allocation assignment). Individuals masked to treatment assignment assessed outcomes. Complete follow-up occurred for 97% of the patients at 6 months. Using intention-to-treat analysis, stable anticoagulation control occurred in significantly more patients taking vitamin K supplementation than in patients taking placebo (54% vs 21%; number needed to treat = 3; 95% CI, 2-10). Daily warfarin dose requirements also increased in significantly more patients in the vitamin K group than in patients in the placebo group (16% vs 1.5%, respectively). No adverse events occurred in either treatment group.

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