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.