Warfarin Toxicity

Exam Cram

• Warfarin is a vitamin K antagonist

• Vitamin K reverse warfarin slowly, can be IV or PO

• PCC (prothrombin complex) reverses quicker and should be used in emergencies

BLeeding & Raised INR

See excellent diagram below from Gram Project [1]. 

First classify bleeding

1. Major: IV Vit K + PCC

2. Minor: IV Vit K

3. No bleeding

   1. INR > 8: PO Vit K

   2. INR 5-8: omit warfarin dose, no vit K

   3. INR < 5: reduce warfarin dose

Operations

Major operation on warfarin

Before

Elective

• Stop warfarin for 4 days prior and cover with treatment dose low molecular weight heparin

Emergency

• If INR 5.0 requires IV Vit K & PCC

After

Med Reg Notes

Reversal Agents

• PCC is combination of factors 2, 7, 9, 10 with protein S and C

• FFP contains clotting factors- more broad collection

• Vitamin K will reverse the effect of warfarin, more slowly

Resources and References

1. https://gramproject.com/diagram/management-of-high-inr-in-warfarin-use/

Written in 2025