Dietary vitamin K intake and anticoagulation in elderly patients.
OBJECTIVE
Vitamin K is an essential co-factor for the synthesis of several coagulation factors. Oral anticoagulants competitively inhibit enzymes that participate in vitamin K metabolism. The purpose of this review is to evaluate the potential interaction of dietary vitamin K and coagulation stability, particularly in the elderly patient.


RESULTS
Recent prospective evidences suggest that dietary vitamin K plays an essential role in anticoagulation stability. Vitamin K intake of more than 250 microg/day was shown to decrease warfarin sensitivity in anticoagulated patients consuming regular diets. In a randomized crossover study, brief periods of changes on vitamin K intake also had significant effects on coagulation parameters. Patients that were allocated to an 80% decrease of intake increased International Normalized Ratio (INR) by almost 30% 7 days after the intervention. Similarly, it was estimated by dietary records that for each increase in 100 microg of vitamin K intake, the INR would be reduced by 0.2. A recent study also demonstrated that over-the-counter multivitamin supplements contain enough vitamin K1 to significantly alter coagulation parameters.


CONCLUSIONS
Contemporary data strengthen the concept that the interaction between dietary vitamin K and coumarin derivatives is clinically relevant and plays a major role in INR fluctuations in chronic anticoagulated patients.
Rohde
Luis Eduardo
LE
Cardiovascular Division of Hospital de Clínicas de Porto Alegre, Post-Graduation Program in Cardiovascular Sciences and Cardiology, Federal University of Rio Grande do Sul, Brazil. lerohde@terra.com.br
de Assis
Michelli Cristina Silva
MC
Rabelo
Eneida Rejane
ER
D000368:Aged; D000375:Aging / Q000097:blood*; D000925:Anticoagulants / Q000008:administration & dosage* / Q000627:therapeutic use; D000933:Antifibrinolytic Agents / Q000008:administration & dosage*; D001777:Blood Coagulation / Q000187:drug effects*; D004032:Diet; D018565:Food-Drug Interactions; D006801:Humans; D010644:Phenprocoumon / Q000008:administration & dosage; D013927:Thrombosis / Q000517:prevention & control; D014812:Vitamin K / Q000008:administration & dosage*; D014859:Warfarin / Q000008:administration & dosage
D000925:Anticoagulants; D000933:Antifibrinolytic Agents; D014812:Vitamin K; D014859:Warfarin; D010644:Phenprocoumon