Warfarin sensitivity: be aware of genetic influence.

BACKGROUND avoidance of over anticoagulation in response to warfarin therapy would reduce risk of associated bleeding. SUBJECTS two elderly patients with venous thromboembolism exhibited extreme anticoagulant response to warfarin. Both were noted to have variant CYP2C9 alleles, which reduce the metabolic capacity of cytochrome P450 2C9. DISCUSSION adverse outcomes with warfarin therapy could be explained and possibly avoided by identifying patients with variant alleles for CYP2C9 before initiation of therapy.