Racial background is a determinant factor in the maintenance dosage of warfarin.

Warfarin is a drug commonly used in the prevention of thromboembolic events. There have been reports suggesting that racial background may influence warfarin dose requirements. Malaysia is a multiracial country in which there are 3 major races, Malay, Chinese, and Indian. We examined 100 patients from our hospital on stable maintenance doses of warfarin, with international normalized ratio (INR) of 2.0 to 3.5. We found that the mean warfarin dose for Indian patients (n = 19) was 6.9 mg, for Chinese patients (n = 55) was 3.6 mg, and for Malay patients (n = 26) was 3.2 mg. The results showed that the Indian patients required a statistically significantly higher warfarin dose than did patients of the other 2 races (P < .0005). Age was also found to affect the daily warfarin maintenance dose.