Cofactor for γ-glutamyl carboxylase, which γ-carboxylates glutamate residues on vitamin-K-dependent proteins (coagulation factors II, VII, IX, X; protein C/S; osteocalcin; matrix Gla protein). The reduced (hydroquinone) form is oxidised during carboxylation and recycled by vitamin-K epoxide reductase (VKOR, blocked by warfarin). K1 is predominantly hepatic → clotting factors.
Half-Life (t½)
PO: 1.5h, IV: 1.5h
Dosing Guidelines
PO: Typical 100 mcg (Range: 90–120 mcg)
IV: Typical 100 mcg (Range: 90–120 mcg)
IM: Typical 100 mcg (Range: 90–120 mcg)
Target Organ Systems
digestive
immune-hematologic
Interactions
Warfarin (major): K1 is warfarin's direct antagonist. Large K1 swings destabilise INR; keep intake consistent if on warfarin. [Holbrook 2005]
Menadione (synergistic): Oral K1 is also catabolised to menadione in the gut before tissue MK-4 synthesis.