Yonsei Med J.  2005 Dec;46(6):843-846.

A Case of Intolerance to Warfarin Dosing in an Intermediate Metabolizer of CYP2C9

• Lee SY
• Kim JS
• Kim JW

Abstract

We report a case of intolerance to warfarin dosing due to impaired drug metabolism in a patient heterozygous for the CYP2C9*3 allele. A 30-year-old woman with an artificial cardiac pacemaker was taking warfarin to prevent thromboembolism. This patient had an extremely elevated international normalized ratio (INR) of prothrombin time (PT) following standard doses of warfarin and experienced difficulties during the induction of anticoagulation. Genotyping for CYP2C9 revealed that this patient was an intermediate metabolizer with genotype CYP2C9*1/*3. 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

Warfarin/administration & dosage/*adverse effects/metabolism
Prothrombin Time
Polymorphism, Genetic
Humans
Female
Dose-Response Relationship, Drug
DNA Mutational Analysis
Aryl Hydrocarbon Hydroxylases/*genetics/metabolism
Anticoagulants/administration & dosage/*adverse effects/metabolism
Adult

Figure

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  Fig. 1 Time course of warfarin therapy and international normalization ratio of prothrombin time.

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  Fig. 2 Detection of nucleotide changes by sequencing analysis of CYP2C9 gene in the individual heterozygous for the CYP2C9*3 allele with A1075C (Ile359Leu) substitution.

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