Weekly warfarin dose requirement (mg) by genotype. (A) VKORC1 genotype: GG wild-type homozygotes, GA heterozygotes, and AA homozygotes. (B) CYP2C9 genotype: *1/*1, wild-type homozygotes; *1/*x: CYP2C9*2 or CYP2C9*3 heterozygotes; and *x/*x: CYP2C9*2 or CYP2C9*3 homozygotes or compound heterozygotes. NS indicates nonsignificant