Vitamin K dependent clotting factors made in the liver include the clotting factors II, VII, IX and X as well as the anticoagulant proteins, protein C and protein S. Warfarin is a Vitamin-K antagonist and works to block its effects in the production of these clotting factors. Tests used to measure these clotting factors include the PT/INR which become prolonged with the use of warfarin. Warfarin therapy is closely monitored via the PT/INR tests to avoid toxicities such as the formation of clots/stroke etc.
If a patient comes in with a very high INR and needs an urgent reversal of the drug (such as in acute major bleeding/ trauma, urgent surgery or invasive procedure, actively bleeding etc), we can give prothrombin complex concentrate (PCC, trade name K centra). PCC contains clotting factors II, VII, IX and X as well as protein C and protein S.
Dosing of Kcentra depends on the patient's weight and pre-treatment INR level.
dosing for warfarin reversal:
INR Dose (IU/kg) Max Dose (IU)
2-4 25 2500
4-6 35 3500
>6 50 5000
*Sometimes we get consulted for patients (such as those with liver disease) who are not taking warfarin, but are found to have an elevated INR, but need an emergent surgery/procedure. This is off-label usage, but our experience of giving typically a lower dose (10-15 units/kg) for these patients has had no adverse effects thus far. Consult your Pathologist prior to making any decision.
For more details about dosing Kcentra, visit the manufacturer's website: http://www.kcentra.com
They also have an app you can download for dosing assistance. (I am in no way affiliated with this company and do not receive any financial reimbursement for this endorsement.)
I have also made a calculator (among many other transfusion medicine handy-dandy calculators) that you can access from this website simply by clicking on the "Calculators" tab at the top of the screen.