The anticoagulant effect of warfarin varies greatly among individuals. Some of this
variability is attributed to differences in the activity of CYP2C9, the predominant enzyme
involved in the metabolism of S-warfarin.
The present study is designed to define the differences in warfarin metabolism among healthy
individuals carrying different CYP2C9 genotypes. In addition, the study will define the
correlation between the phenytoin metabolic ratio, a marker of CYP2C9 activity in vivo, and
warfarin metabolism.