Inhibition can lead to increased warfarin levels in the blood, potentially enhancing its anticoagulant effect." Singh says ...

1). During the period of treatment with phenylbutazone the apparent concentration of warfarin in plasma rose to a level of 14 mg. per liter; however, the ultraviolet absorption spectrum was not ...

Data taken from [59–62]. Warfarin is the most well-understood oral anticoagulant in terms of genetics. CYP2C9 and VKORC1 polymorphisms lead to variable dose response and complicate warfarin therapy.