How are warfarin dose adjustments calculated from INR?

For INR in range: no change. INR 1.5–1.9 (target 2–3): increase total weekly dose 10–20%. INR 3.1–3.9: decrease weekly dose 10–20%, recheck in 1–2 weeks. INR 4–5: hold 1 dose, reduce weekly dose 10–15%. INR >5 with no bleeding: hold, give Vitamin K 1–2.5 mg oral, recheck 24h.

How does pharmacogenomics influence warfarin initiation?

VKORC1 -1639 G>A (A/A genotype): requires 25–50% dose reduction. CYP2C9 *2/*3 variants: reduce metabolic clearance. FDA-approved pharmacogenetic dosing algorithms (IWPC, Gage) incorporate genotype + clinical factors to predict maintenance dose, reducing time to therapeutic INR vs fixed initiation protocols.

Warfarin Dose Adjustment from INR and VKORC1

Calculate warfarin dose adjustment based on current INR, target INR range, and VKORC1/CYP2C9 genotype to achieve and maintain anticoagulation targets safely.

Use the full interactive calculator below, or

Warfarin Dose Adjustment from INR and VKORC1

Frequently Asked Questions

How are warfarin dose adjustments calculated from INR?

How does pharmacogenomics influence warfarin initiation?