Vitamin K

An essential co-factor in the synthesis of clotting factors II, VII, IX and X. It is used for the reversal of coumadin-induced coagulopathy.

Warfarin overdose, no therapeutic need for warfarin (i.e. took someone else’s):

• Give 5 mg of vitamin K PO or IV daily for 2 days and recheck INR in 48 hours.

Warfarin overdose, therapeutic need for warfarin:

• Closely monitor INR every 6 hours. Give 0.5 – 2 mg IV if INR > 5.
• Give repeated doses if INR remains over 5.
• If INR falls below 2, start heparin if there is an absolute indication for anticoagulation.

Ingestion of long-acting anticoagulant rodenticide:

• Very large doses of oral vitamin K are required for a period of weeks to months if anticoagulation occurs.
• Initially very close monitoring of the INR will be needed to establish the correct oral dose required.
• Active bleeding or a high-risk of bleeding (INR > 9) requires immediate reversal of anticoagulation by the administration of prothrombin complex concentrate and fresh frozen plasma, in addition to vitamin K.

References

• Bruno GR et al.  Long-acting anticoagulant overdose: brodifacoum kinetics and optimal vitamin K dosing.  Annals of Emergency Medicine 2000; 36(3):262-267.
• Isbister GK, Hackett LP and Whyte IM.  Intentional warfarin overdose.  Therapeutic Drug Monitoring 2003; 25(6):715-722.
• Baker RI, Coughlin PB, Gallus AS et al.  Warfarin reversal: consensus guidelines, on behalf of the Australasian Society of Thrombosis and Haemostasis. Medical Journal of Australia 2004; 181(9):492-497.
• Dentali F, Ageno W, Crowther M.  Treatment of coumarin-associated coagulopathy: a systematic review and proposed treatment algorithms. Journal of Thrombosis and Haemostasis 2006; 4:1853-1863.