Low dose daily vitamin K supplementation in patients anticoagulated with warfarin

Excerpt

A low intake of dietary vitamin K has been associated with unstable anticoagulation. Since the 1960s it has been hypothesized that oral vitamin K supplementation may reduce unexplained INR variability. Beginning in 2000, oral vitamin K 100 micrograms daily was implemented as a clinical management tool for patients with unstable anticoagulation and a low self-reported intake of dietary vitamin K. We retrospectively reviewed the anticoagulation control for patients who received daily vitamin K supplements from 2000 to 2006. The primary outcome was the percentage of INR values within target range before and after implementation of daily oral vitamin K. The variability of the INR was tested by the two-sided Wilcoxon test. Eighteen patients with unstable anticoagulation received vitamin K supplementation. Low dose oral vitamin K increased the rate of INR values within the patient-specified target range from 30.8% to 40.1%. Eleven of eighteen patients (61%) had an increase in the percentage of INR values within target range. Although the coefficient of variation was not statistically significant, these results support the findings of other studies supplementing vitamin K. The apparent improvement in anticoagulation control with vitamin K supplementation has prompted initiation of a larger study at our institution. …