title: The impact of genetics on the management of patients on warfarin awaiting surgery.
abstract: Two older patients with atrial fibrillation, receiving warfarin for thromboembolic prophylaxis, with a target range of 2.0-3.0, were significantly over anticoagulated prior to elective intervention, in spite of having adhered to the standard protocol of 5 days of warfarin interruption. Neither patient had any abnormality of liver function nor was taking any interacting drug known to inhibit warfarin metabolism or affect sensitivity to warfarin. Both had variant cytochrome P2C9 (CYP2C9) alleles which reduce the metabolic capacity of the CYP2C9 enzyme responsible for the metabolism of the S-warfarin enantiomer. Need for preoperative administration of vitamin K or postponement of an operation because of an INR >1.5 could be explained by variant alleles for CYP2C9 and age.
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
authors.forename: Salah
authors.initials: S
authors.lastname: Abohelaika
authors.affiliation: Department of Older People's Medicine, Newcastle upon Tyne Hospitals NHS Foundation Trust, Freeman Hospital, Freeman Road, High Heaton, Newcastle upon Tyne NE7 7DN, UK.
authors.forename: Hilary
authors.initials: H
authors.lastname: Wynne
authors.affiliation: Department of Radiology, South Tyneside NHS Foundation Trust, South Tyneside District Hospital, Tyne and Wear NE34 0PL, UK.
authors.forename: Lance
authors.initials: L
authors.lastname: Cope
authors.affiliation: Institute of Cellular Medicine, Newcastle University, Newcastle upon Tyne NE1 7RU, UK.
authors.forename: Farhad
authors.initials: F
authors.lastname: Kamali
mesh_terms: D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use; D001281:Atrial Fibrillation / Q000150:complications / Q000601:surgery; D017115:Catheter Ablation; D004305:Dose-Response Relationship, Drug; D005838:Genotype; D006801:Humans; D008297:Male; D011110:Polymorphism, Genetic; D057234:Preoperative Period; D013923:Thromboembolism / Q000209:etiology / Q000235:genetics* / Q000517:prevention & control; D014859:Warfarin / Q000627:therapeutic use*
chemical_list: D000925:Anticoagulants; D014859:Warfarin
keywords: anticoagulation; older people; pharmacogenetics; warfarin