Warfarin Dosing and Monitoring
Several factors can influence an individual’s warfarin dose requirement, including body size, age, diet and genetics.
Variation in the VKORC1 gene (encoding the target of warfarin) and the CYP2C9 gene (encoding the primary metabolizer of warfarin) explain a large proportion of the dose variation. Variation in the GGCX gene and CYP4F2 gene also affect the dose requirements. Individuals who have taken genetic testing can go to www.warfarindosing.org to see how their genetics can assist in making proper dosing decisions.
International Normalised Ratio (INR) testing
Regular measurement of INR levels is an essential component in the management of patients receiving warfarin treatment. Determining the correct warfarin dose to achieve an INR of 2-3 can be very challenging due to the wide variation in responses to warfarin. The time taken to achieve this stable INR can take weeks to months, and during that time the patient is often at an increased risk of either hemorrhage or thrombosis. Determining an individual’s genetic variation for each of the genes mentioned above, significantly reduces the time taken to achieve a stable INR.
About the Warfarin Sensitivity DNA Test »
Pavani A, Naushad SM,
Rupasree Y, Kumar TR, Malempati AR, Pinjala RK, Mushra RC, Kutala VK (2012). Optimization of warfarin dose by population-specific pharmacogenomic algorithm. Pharmacogenomics J. 12(4): 306-11.