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Major Bleeding Caused by Warfarin in a Genetically Susceptible Patient
Author(s) -
Bloch Aharon,
BenChetrit Eldad,
Muszkat Mordechai,
Caraco Yoseph
Publication year - 2002
Publication title -
pharmacotherapy: the journal of human pharmacology and drug therapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.227
H-Index - 109
eISSN - 1875-9114
pISSN - 0277-0008
DOI - 10.1592/phco.22.1.97.33491
Subject(s) - warfarin , cyp2c9 , medicine , fresh frozen plasma , heterozygote advantage , allele , anticoagulant , pharmacology , cytochrome p450 , gastroenterology , anesthesia , surgery , chemistry , gene , biochemistry , metabolism , platelet , atrial fibrillation
A 90‐year‐old woman was hospitalized for gastrointestinal bleeding. Although she had been receiving only warfarin 5 mg/day, her international normalized ratio (INR) was 66. Warfarin was discontinued, and her INR fell to 3.7 after transfusion of fresh‐frozen plasma. However, it rose again spontaneously to 7.5. Eleven days after the last dose of warfarin had been administered, it was still detectable in the patient's plasma, indicating that impaired warfarin clearance may have caused an enhanced anticoagulation effect. Genetic analysis of the cytochrome P450 (CYP) isoenzyme 2C9, which mediates the major deactivating pathway of S‐warfarin, revealed that the patient was a compound heterozygote carrying two variant alleles: CYP2C9*2 and CYP2C9*3 . The patients enhanced sensitivity to warfarin 5 mg/day can be ascribed to decreased clearance of S‐warfarin secondary to genetic alteration of the gene encoding CYP2C9, resulting in a life‐threatening complication.