Possible Interaction: Vitamin K and Warfarin

“ Vitamin K is reported to begin reversing warfarin within 6 to 12 hours, but this may occur sooner.”

“The results of the present study suggest that the capacity of dietary vitamin K intake to influence warfarin dose requirements during anticoagulation therapy is VKORC1 genotype-dependent, at least in part.”

“CONCLUSIONS A single 1 mg intravenous dose of vi amin K si gnificantly reduces the time for the reversal of INR and the pre-operative delay to surgery, in patients on long-term war farin. ”

“Data suggest that warfarin can be used as a safe and accurate biomarker for CYP2C9, and if warfarin is administered with vitamin K , the pharmacodynamic effect is ablated.”

“Clinical Implications Clinicians should consider oral administration when prescribing vitamin K for patients who become overanticoagulated while receiving warfarin.”

“Context Giving vitamin K when stopping warfarin increases the rate at which the international normalized ratio (INR) returns to normal.”

“… vitamin K administration … receiving warfarin who have asymptomatic excessive prolongations in their INR results, 1 mg of oral vitamin K reliably reduces the INR to the therapeutic …, it should be considered in all non-bleeding patients receiving warfarin, who present with INR results of 4.5 to 9.5.”

“3) The above mentioned results of (1) and (2) suggest that it is important for development of anticoagulant effects by warfarin to inhibit conversion from vitamin K1 to reduced vitamin K1, as well as to inhibit the reducing process from vitamin K1-epoxide to vitamin K1. (”

“Dietary vitamin K should be regarded as an important environmental factor contributing to unwanted disturbances in warfarin‐induced anticoagulation.”

“Administration of a pharmacological dose of vitamin K1 together with the enantiomers of warfarin was necessary clinically and resulted in elevation of vitamin K1 2,3-epoxide concentrations, which were similar in each case.”

“The protective effect of vitamin K2 could be abolished by adding warfarin , a vitamin K2 antagonist.”