Effect of low-dose supplements of menaquinone-7 (vitamin K2) on the stability of oral anticoagulant treatment: dose-response relationship in healthy volunteers

Theuwissen E, Teunissen KJ, Spronk HM, et al. · Journal of Thrombosis and Haemostasis

The number that decides who should not take this: 45 ug/day of MK-7 cut mean INR and uncarboxylated factor II by about 40%, and even 10 ug/day — a fraction of a typical 100-200 ug capsule — produced a clinically relevant INR fall in at least 40% of subjects. The authors conclude MK-7 supplements must be avoided during vitamin-K-antagonist therapy.

Population

Healthy men and women anticoagulated with acenocoumarol to a target INR of 2.0, then given rising MK-7 doses over six weeks

Intervention

MK-7 at 10, 20 and 45 ug/day on top of established anticoagulation

Comparator

Their own stable anticoagulated baseline

Limitations

Eighteen healthy volunteers anticoagulated experimentally rather than patients on long-term therapy; sequential dose escalation without a placebo arm; INR is a surrogate for bleeding or clotting events.