Observations on possible effects of daily vitamin K replacement, especially upon warfarin therapy.

Daily parenteral vitamin K supplement is now recommended by the U.S. Food and Drug Administration (FDA) for patients receiving IV hyperalimentation. This is considered as preferable to the previous recommendations of weekly parenteral or oral supplement, or as in some cases no supplement at all. Supplemental vitamin K1 will ensure adequate supplies for hepatic saturation and thus the production of clotting factors II, VII, IX, and X, plus the anticoagulants protein C, protein S, and protein Z. But this is not the entire story. This recommended supplement will affect other physiologic systems that also use vitamin K-dependent gamma-carboxylation. Vitamin K is not 1 molecule but rather 2 natural substances, vitamin K1 and K2, and the synthetic K3's. It is not understood, what, if any, effect may occur because of the saturation or competition from the vitamin K1 upon the functioning of vitamins K2 and the derivatives of K3 in vivo upon bone mineralization, cell growth, and blood vessel health, all known to be influenced by the vitamins K. There are probably other physiologic systems yet to be studied relative to vitamins K and gamma-carboxylation. This review also considers the available research upon warfarin when given to patients receiving hyperalimentation and what effects the vitamin K supplements may have. Because studies to date have not controlled for vitamin K intake, consideration is given to whether one should expect any change in previously reported outcomes when using low-dose warfarin for prophylaxis against central vein thrombosis. Also considered are possible positive or negative effects that chronic warfarin therapy may have upon the other vitamin K-dependent systems under discussion. This review offers a platform for further discussion and derived clinical research provoked by this new FDA recommendation.