Intersubject variation of warfarin binding to protein in serum of normal subjects.

The protein binding of warfarin was determined in the serum of 18 normal adult subjects (8 males and 10 females). A statistically significant negative correlation between free fraction of warfarin and albumin concentration was found. The free fraction of warfarin in the serum of women was significantly larger than that in the serum of men, apparently due to the lower albumin concentration in the serum of women.