J Korean Med Sci.  2007 Jun;22(3):557-559. 10.3346/jkms.2007.22.3.557.

A Case Report of a Patient Carrying CYP2C9*3/4 Genotype with Extremely Low Warfarin Dose Requirement

• Lee SY
• Nam MH
• Kim JS
• Kim JW

• KMID: 1778371
• DOI: http://doi.org/10.3346/jkms.2007.22.3.557

Abstract

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.

Keyword

Warfarin; Cytochrome P-450 CYP2C9; Polymorphism; Prothrombin Time; Pharmacogenetics

MeSH Terms

Aged
Anticoagulants/pharmacology
Aryl Hydrocarbon Hydroxylases/*genetics
Atrial Fibrillation/*drug therapy/*genetics
Female
*Genotype
Heterozygote
Humans
International Normalized Ratio
Pharmacogenetics
Polymorphism, Genetic
Prothrombin Time
Warfarin/*pharmacology

Figure

• 

  Fig. 1 Detection of nucleotide changes by sequencing analysis of CYP2C9 gene in the patient with CYP2C9*3/*4 showing A1075C (Ile359Leu) and A1076T (Ile359Thr) substitutions (indicated by arrows).

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