The first specific PGx testing application most labs are likely to encounter is that used in patients taking warfarin.

Recent studies have revealed that the variations seen in patients taking the anticoagulant warfarin are due to PGx factors. The consequences of incorrect warfarin dosing are obviously serious, with inadequate doses predisposing patients to thrombosis and higher doses placing them at risk for hemorrhage.

The United States' Food and Drug Administration (FDA) recently approved updated labeling for Coumadin (warfarin sold by Bristol-Myers Squibb). The new labeling suggests that physicians incorporate PGx information into warfarin-dosing regimens for patients. Manufacturers of generic warfarin products are now adding similar labeling.