A case report of a patient carrying CYP2C9*3/4 genotype with extremely low warfarin dose requirement.
We report a case of intolerance to warfarin dosing due to impaired drug metabolism in a patient with CYP2C9*3/*4. A 73-yr-old woman with atrial fibrilation was taking warfarin. She attained a high prothrombin time international normalized ratio (INR) at the standard doses during the induction of anticoagulation and extremely low dose of warfarin (6.5 mg/week) was finally chosen to reach the target INR. Genotyping for CYP2C9 revealed that this patient had a genotype CYP2C9*3/*4. This is the first Korean compound heterozygote for CYP2C9*3 and *4. This case suggests the clinical usefulness of pharmacogenetic testing for individualized dosage adjustments of warfarin.
Lee
Soo Youn
SY
Department of Laboratory Medicine, Samsung Medical Center, Sungkyunkwan University School of Medicine, Seoul, Korea.
Nam
Myung Hyun
MH
Kim
June Soo
JS
Kim
Jong Won
JW
D000368:Aged; D000925:Anticoagulants / Q000494:pharmacology; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D001281:Atrial Fibrillation / Q000188:drug therapy* / Q000235:genetics*; D065729:Cytochrome P-450 CYP2C9; D005260:Female; D005838:Genotype; D006579:Heterozygote; D006801:Humans; D019934:International Normalized Ratio; D010597:Pharmacogenetics; D011110:Polymorphism, Genetic; D011517:Prothrombin Time; D014859:Warfarin / Q000494:pharmacology*
D000925:Anticoagulants; D014859:Warfarin; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases