Variant CYP2C9 alleles and warfarin concentrations in patients receiving low-dose versus average-dose warfarin therapy.

This study compared the frequency of variant cytochrome P450 2C9 (CYP2C9) alleles and warfarin S/R concentration ratio in patients who required low-dose (<2.5 mg/day) and average-dose (5+/-0.5 mg/day) warfarin.

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.