CYP2C9 genetic polymorphisms and warfarin.
The objective of this study was to report 2 cases of CYP2C9 genetic polymorphism and elevated warfarin S:R ratios in patients taking low doses of warfarin, and compare the observed characteristics with those in published reports. Two patients of different age groups and races were evaluated for CYP2C9 genotype and warfarin S:R ratios. The patients had been stabilized on weekly warfarin doses of 10.5 mg and 10 mg, respectively. Each patient was found to have at least 1 variant CYP2C9 allele. Elevated warfarin S:R ratios in both patients provided evidence for impaired metabolism of S-warfarin. This report of a CYP2C9*3 heterozygous individual taking a low dose of warfarin is consistent with previous reports in the literature. This summary of a CYP2C9*6 homozygous individual taking a low dose of warfarin is the first such published report. CYP2C9 genotyping in these patients provided a likely explanation for their continued low warfarin dosage requirements. Awareness of a patient's CYP2C9 genotype may provide an explanation for low warfarin dosage requirements in stable patients and may help in determining the optimal dose in patients being initiated on warfarin.
Redman
Andrea R
AR
Department of Clinical and Administrative Sciences, Mercer University Southern School of Pharmacy, Atlanta, Georgia 30341-4155, USA. Redman_ar@mercer.edu
Dickmann
Leslie J
LJ
Kidd
Robert S
RS
Goldstein
Joyce A
JA
Ritchie
Denise M
DM
Hon
Yuen Yi
YY
D000328:Adult; D001741:Black or African American / Q000235:genetics; D000368:Aged; D001189:Aryl Hydrocarbon Hydroxylases / Q000235:genetics*; D065729:Cytochrome P-450 CYP2C9; D006801:Humans; D008297:Male; D010597:Pharmacogenetics; D011110:Polymorphism, Genetic / Q000235:genetics*; D013237:Stereoisomerism; D014859:Warfarin / Q000008:administration & dosage / Q000737:chemistry / Q000494:pharmacology*
D014859:Warfarin; C450260:CYP2C9 protein, human; D065729:Cytochrome P-450 CYP2C9; D001189:Aryl Hydrocarbon Hydroxylases