Does ethnicity play a role in the dosing of warfarin in Hawai'i?

Warfarin is the most common anticoagulant prescribed and its metabolism has been linked to two specific genes, CYP2C9 and VKORC1. This study analyzed 113 patients from 4 different ethnic backgrounds (Asian, Native Hawaiian, Portuguese, and Caucasian) and investigated the association between the mean daily dose of warfarin and ethnicity. Caucasian patients required the highest mean daily dose of warfarin 4.4 mg/day while Asian patients required the lowest mean daily dose of warfarin 2.5 mg/day. Portuguese patients and Native Hawaiian patients required mean of 3.8 mg/day. All three groups required a significantly lower dose than Caucasians. When adjusted for weight in kilograms, Native Hawaiian patients required a dose of 4.3 × 10(-2) mg/kg, Portuguese 4.4 × 10(-2) mg/kg and Asians 4.0 × 10(-2) mg/kg. These three populations had similar mean milligrams/kilogram dose requirements while Caucasians required a significantly higher dose of 5.3 × 10(-2) mg/kg. This data suggests that ethnicity should be taken into consideration when dosing warfarin.