Four determinants of the INR response are:

1) Dose,

2) Diet (vitamin K antagonizes warfarin),

3) Drugs,

4) Disease

Indications for INR Goal 2.5; range 2.0-3.0: prophylaxis of venous thrombosis (high risk surgery); treatment of venous thrombosis; treatment of pulmonary embolism; prevention of systemic embolism (tissue heart valves, acute MI, valvular heart disease, atrial fibrillation); bileaflet mechanical valve in aortic position, normal sinus rhythm


Indications for INR Goal 3.0; range 2.5-3.5: mechanical prosthetic valves (high risk); certain pts with thrombosis and the antiphospholipid syndrome, acute MI (to prevent recurrence)


The INR (International Normalized Ratio) is a unit-less number. INRs into the 4 range you’ll begin to see bleeding, not necessarily hemorrhaging. The effects of different INR readings depend on the individual pt and their disease condition.


Often, when the MD wants to titrate the INR to a certain number, they must adjust the dose of Coumadin daily, up and down, to get the intended INR. It is a very tedious titration. Low-dose warfarin (1mg) as an anti-viscosity medication is not a legitimate indication.

Category: Pharmacology Notes