Factors determining the maintenance dose of warfarin in Chinese patients

Chinese patients are reportedly more sensitive than Caucasians to theanticoagulant effect of warfarin. We examined warfarin dose requirementsand their determinants in 151 Chinese out-patients on stable maintenancedose of warfarin with international normalized ratio of 2 to 2.5. Meandaily warfarin requirement was 3.3 +/- 1.4 mg, much lower than reporteddoses in Caucasian patients. The most important determinant was age (r =-0.43, p < 0.001), with progressively lower warfarin requirement withincreasing age (p = 0.0001). There was a weaker association with bodyweight (r = 0.20, p = 0.01). Patients with chronic rheumatic heart diseasetended to require a smaller dose than those with heart valve replacements(2.94 +/- 1.24 vs. 3.69 +/- 1.42 mg, p < 0.01). We confirm that Chinesepatients require a smaller dose of warfarin for the same degree ofanticoagulation. Age is the most important factor affecting doserequirement, although body weight and underlying disease also play a role.