VKORC1 and Thromboembolism: Certain single nucleotide polymorphisms in the VKORC1 gene (especially the 1639G>A allele) have been associated with lower dose requirements for warfarin.(57) Different dosing algorithms have been proposed for warfarin considering age, sex, weight, or body surface area, race, use of other drugs (such as amiodarone, simvastatin, any azole), treatment indication (heart valve prosthesis, thromboembolic disease), INR, and VKORC1 (3673G>A) and CYP2C19 (*2, *3, *5) polymorphisms.(57,58)