Key result
Variant cytochrome P2C9 (CYP2C9) alleles and age explained significant over-anticoagulation (INR >1.5) prior to elective surgery in two patients despite a standard 5-day warfarin interruption.
Why the study?
Do variant CYP2C9 alleles explain persistent over-anticoagulation despite standard 5-day warfarin interruption in older patients with atrial fibrillation awaiting surgery?
Case Report (n=2)
Do variant CYP2C9 alleles explain persistent over-anticoagulation despite standard 5-day warfarin interruption in older patients with atrial fibrillation awaiting surgery?
Variant CYP2C9 alleles and age can explain persistent over-anticoagulation in patients on warfarin despite a standard 5-day preoperative interruption.
Answers are grounded in this paper and cite their sources.
May prompt CYP2C9-informed warfarin holds in select elderly AF patients; leaves open prospective validation before practice change.
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.
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Abohelaika et al. (2015) conducted a case report in Atrial fibrillation on warfarin awaiting surgery (n=2). Variant cytochrome P2C9 (CYP2C9) alleles was evaluated on Over-anticoagulation (INR >1.5) prior to elective intervention despite 5 days of warfarin interruption. Variant cytochrome P2C9 (CYP2C9) alleles and age explained significant over-anticoagulation (INR >1.5) prior to elective surgery in two patients despite a standard 5-day warfarin interruption.
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