Warfarin Management Guidelines

Introduction to Warfarin Therapy

The American Geriatrics Society recommends monitoring INR daily until stable therapeutic range is achieved, then progressively lengthen intervals based on stability 1
The European Heart Journal suggests that INR monitoring should be done daily after the first dose until PT/INR stabilizes in therapeutic range, then 2-3 times weekly for 1-2 weeks 2

The American Geriatrics Society recommends weekly measurements for 1 month, and every 1-2 months if stability is maintained 1
The European Heart Journal suggests that fluctuations in diet and weight, changes in concomitant medications, and intercurrent illness require increased monitoring 1, 2

For INR 4.0-5.0, the American Geriatrics Society recommends withholding warfarin and observing, with no vitamin K needed unless high bleeding risk factors are present 3
For INR 5.0-9.0, the European Heart Journal suggests withholding 1-2 doses of warfarin and monitoring serial INR determinations, with oral vitamin K 1.0-2.5 mg only if increased bleeding risk factors are present 1, 5
For INR >9.0-10.0, the American Geriatrics Society recommends immediately withholding warfarin and administering oral vitamin K 2.5-5 mg, with INR rechecked within 24 hours 1, 2

For major bleeding, the European Heart Journal suggests administering 5-10 mg IV vitamin K by slow infusion over 30 minutes, and stopping warfarin immediately 2, 3, 4
For life-threatening bleeding or emergency surgery, the American Geriatrics Society recommends immediately administering 4-factor prothrombin complex concentrate (PCC) 25-50 U/kg IV plus vitamin K 5-10 mg by slow IV infusion over 30 minutes, targeting INR <1.5 5, 3, 4

The European Heart Journal recommends replacing warfarin with heparin during the first trimester and last 6 weeks before delivery in pregnant women 2
The American Geriatrics Society suggests that age alone is not an independent predictor of bleeding, but should be considered in context of other risk factors 1

The American Geriatrics Society warns that warfarin is highly protein-bound (97-99%), making it susceptible to drug-drug interactions 1, 2
The European Heart Journal notes that liver disease and nutritional deficiency leading to reduced protein/albumin levels increase bleeding risk by increasing free drug fraction 1, 2