Vitamin K intake, body mass index and warfarin maintenance dose.
BACKGROUND
Warfarin inhibits vitamin K-dependent coagulation factors. Being fat-soluble, the availability of vitamin K may vary according to body fat. We hypothesized that body mass index (BMI), a proxy of body fat, may interact with vitamin K intake in determining a warfarin maintenance (WM) dose.


METHODS
Patients with data on vitamin K intake, potential confounders and WM dose (n = 172) were included in linear regression models to test whether BMI modifies the relation between vitamin K intake and WM dose.


RESULTS
Warfarin loading dose correlated with the maintenance dose (r = 0.36, p < 0.0001) but was not significantly associated with WM dose in analyses adjusted for vitamin K epoxide reductase (VKORC1) and cytochrome P450 2C9 (CYP2C9) genotypes. In fully adjusted models, BMI was associated (p = 0.001) with WM dose but vitamin K was only marginally positively associated (p = 0.06) with WM dose. We found no interaction (p > 0.05) between BMI and vitamin K intake with regard to WM dose. Inclusion of vitamin K intake in the model only slightly improved the amount of variance (1.1%) explained by age, gender, BMI, race, physical activity, energy intake and VKORC1 and CYP2C9 genotypes.


CONCLUSIONS
Our data suggest that body fat does not affect the relation between vitamin K intake and WM dose.
Division of Epidemiology, Department of Medicine, Vanderbilt University Medical Center, Nashville, Tenn., USA.
Edmond K
EK
Kabagambe
T Mark
TM
Beasley
Nita A
NA
Limdi
D000368:Aged; D000369:Aged, 80 and over; D000925:Anticoagulants / Q000008:administration & dosage*; D015992:Body Mass Index; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D010597:Pharmacogenetics; D011446:Prospective Studies; D014812:Vitamin K / Q000008:administration & dosage*; D014859:Warfarin / Q000008:administration & dosage*
D000925:Anticoagulants; D014812:Vitamin K; D014859:Warfarin