Vitamin K intake and sensitivity to warfarin in patients consuming regular diets.
The effect of dietary vitamin K intake on warfarin sensitivity is known only from case reports and few small clinical studies. We followed 50 patients commencing warfarin and consuming their regular diets (for 8 weeks) to study this relationship. A one-week recall dietary questionnaire was completed at weeks 2 and 8. Daily intake of nutrients and vitamin K was calculated from standard tables. Warfarin sensitivity index (WSI) was defined as final INR/final warfarin dose (mg/day/m2 of body surface area) (week 8). Vitamin K intake was 17-974 (median: 179) microg/day. Median WSI was 0.82 (0.31-4.47). A WSI value of 1.1 significantly separated excess (>250 microg/day) from normal (<250 microg/day) vitamin K consumers (16/18 vs. 15/32, respectively, p <0.01). The former had lower day 5 INR (median: 1.9 vs. 3.0, p <0.001), needed more warfarin to achieve INR > or =2.0 (32.0+/-9.2 mg vs. 25.4+/-6.4 mg, p = 0.009) and required a higher maintenance steady state warfarin dose (5.7+/-1.7 mg/day vs. 3.5+/-1.0 mg/day, p <0.001). We conclude that in 32% (16/50) of anticoagulated patients under usual dietary conditions sensitivity to warfarin is decreased by vitamin K intake > or =250 microg/day.
Lubetsky
A
A
Anticoagulation Clinic, Department of Medicine, Sheba Medical Center, Tel-Hashomer, and Sackler School of Medicine, Tel-Aviv University, Israel.
Dekel-Stern
E
E
Chetrit
A
A
Lubin
F
F
Halkin
H
H
D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000494:pharmacology*; D004032:Diet / Q000009:adverse effects; D004347:Drug Interactions; D004361:Drug Tolerance; D005260:Female; D006490:Hemostatics / Q000008:administration & dosage*; D006801:Humans; D008297:Male; D008875:Middle Aged; D014812:Vitamin K / Q000008:administration & dosage*; D014859:Warfarin / Q000494:pharmacology*
D000925:Anticoagulants; D006490:Hemostatics; D014812:Vitamin K; D014859:Warfarin