Thromb Haemost 1999; 81(03): 396-399
DOI: 10.1055/s-0037-1614485
Review Article
Schattauer GmbH

Vitamin K Intake and Sensitivity to Warfarin in Patients Consuming Regular Diets

Aharon Lubetsky
1   From the Anticoagulation Clinic, Department of Medicine, Tel-Aviv University, Israel
,
Edit Dekel-Stern
1   From the Anticoagulation Clinic, Department of Medicine, Tel-Aviv University, Israel
,
Angela Chetrit
2   Department of Clinical Epidemiology, Sheba Medical Center, Tel-Hashomer, and Sackler School of Medicine, Tel-Aviv University, Israel
,
Flora Lubin
2   Department of Clinical Epidemiology, Sheba Medical Center, Tel-Hashomer, and Sackler School of Medicine, Tel-Aviv University, Israel
,
Hillel Halkin
1   From the Anticoagulation Clinic, Department of Medicine, Tel-Aviv University, Israel
› Author Affiliations
Further Information

Publication History

Received15 May 1998

Accepted after resubmission10 November 1998

Publication Date:
09 December 2017 (online)

Summary

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) μg/day. Median WSI was 0.82 (0.31-4.47). A WSI value of 1.1 significantly separated excess (≥250 μg/day) from normal (<250 μg/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 ≥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 ≥250 μg/day.

 
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