How do vitamin K intake and VKOR genotype affect oral anticoagulation?

• Research type

  Research Study

• Full title

  An investigation of the association between vitamin K intake, vitamin K epoxide reductase subunit (VKORC1) genotype and anticoagulation response to warfarin

• IRAS ID

  9136

• Sponsor organisation

  The Newcastle Upon Tyne Hospitals NHS Foundation Trust

• Eudract number

  2008-006451-52

• ISRCTN Number

  N/A

• Clinicaltrials.gov Identifier

  N/A

• Research summary

  The effect of warfarin, a blood thinning drug used to treat or prevent blood clots, varies from person to person and in each person over time. Because of this people taking warfarin have to have a blood test regularly to check on their blood clotting to try to prevent it from getting too “thick” (likely to clot), due to not enough warfarin, or too “thin (likely to bleed), due to too much warfarin. Vitamin K in the diet, works in the opposite way to warfarin. Several studies have shown that when people have little, or erratic, intake of vitamin K containing foods then their response to warfarin becomes unstable. Warfarin acts on an enzyme in the liver called vitamin K epoxide reductase (VKOR), which exists either in a maximum, medium, or slow activity form. The enzyme form expressed in every individual is fluenced by the vitamin K epoxide reductase gene. Our previous studies suggest that people with the maximum activity form of VKOR are more sensitive tflutuations in dietary intake of vitamin K than those with enzymes of lower activity. We wish to investigate this further in the current study. We will ask 600 patients taking warfarin about their intake of vitamin K containing foods using a short questionnaire. We will take a 20 ml venous blood sample for analysis of their VKORC1 gene type as well as CYP2C9, another gene responsible for controlling warfarin metabolism that we need to allow for in this study. If the study shows that VKORC1 genotype fluences how much a person’s anticoagulation response to warfarin is fluenced by dietary vitamin K intake, then offering tailored dietary advice could be a method which could be used to improve stability of anticoagulant control and thereby improve benefit and reduce risk from treatment for patients taking warfarin.

• REC name

  North East - Newcastle & North Tyneside 2 Research Ethics Committee

• REC reference

  08/H0907/159

• Date of REC Opinion

  26 Jan 2009

• REC opinion

  Further Information Favourable Opinion