Warfarin Sodium

What it is and how it works

Mechanism of Action Warfarin acts by inhibiting the synthesis of vitamin K-dependent clotting factors, which include Factors II, VII, IX, and X, and the anticoagulant proteins C and S. Vitamin K is an essential cofactor for the post ribosomal synthesis of the vitamin K-dependent clotting factors. Vitamin K promotes the biosynthesis of γ-carboxyglutamic acid residues in the proteins that are essential for biological activity. Warfarin is thought to interfere with clotting factor synthesis by inhibition of the C1 subunit of vitamin K epoxide reductase (VKORC1) enzyme complex, thereby reducing the regeneration of vitamin K 1 epoxide .

Indications

Warfarin sodium tablets are indicated for: Prophylaxis and treatment of venous thrombosis and its extension, pulmonary embolism (PE). Prophylaxis and treatment of thromboembolic complications associated with atrial fibrillation (AF) and/or cardiac valve replacement. Reduction in the risk of death, recurrent myocardial infarction (MI), and thromboembolic events such as stroke or systemic embolization after myocardial infarction. Limitations of Use Warfarin sodium tablets have no direct effect on an established thrombus, nor does it reverse ischemic tissue damage. Once a thrombus has occurred, however, the goals of anticoagulant treatment are to prevent further extension of the formed clot and to prevent secondary thromboembolic complications that may result in serious and possibly fatal sequelae.

Dosage and administration (summary)

Individualize dosing regimen for each patient, and adjust based on INR response. ( 2.1 , 2.2 ) Knowledge of genotype can inform initial dose selection. Monitoring: Obtain daily INR determinations upon initiation until stable in the therapeutic range. Obtain subsequent INR determinations every 1 to 4 weeks. Review conversion instructions from other anticoagulants. Individualized Dosing The dosage and administration of warfarin sodium tablets must be individualized for each patient according to the patient’s International Normalized Ratio (INR) response to the drug. Adjust the dose based on the patient’s INR and the condition being treated.

Contraindications

Warfarin sodium is contraindicated in: Pregnancy Warfarin sodium is contraindicated in women who are pregnant except in pregnant women with mechanical heart valves, who are at high risk of thromboembolism . Warfarin sodium can cause fetal harm when administered to a pregnant woman.

Warnings and precautions

Tissue necrosis: Necrosis or gangrene of skin or other tissues can occur, with severe cases requiring debridement or amputation. Discontinue warfarin sodium and consider alternative anticoagulants if necessary. Calciphylaxis: Fatal and serious cases have occurred. Discontinue warfarin sodium and consider alternative anticoagulation therapy. Acute kidney injury may occur during episodes of excessive anticoagulation and hematuria. Systemic atheroemboli and cholesterol microemboli: Some cases have progressed to necrosis or death. Discontinue warfarin sodium if such emboli occur.

Pregnancy

Pregnancy Risk Summary Warfarin sodium is contraindicated in women who are pregnant except in pregnant women with mechanical heart valves, who are at high risk of thromboembolism, and for whom the benefits of warfarin sodium may outweigh the risks . Warfarin sodium can cause fetal harm.

Storage and supply

Warfarin sodium tablets USP, 1 mg are available as pink, capsule-shaped, biconvex scored tablets, debossed with TV/1 on the scored side and 1712 on the other side containing 1 mg warfarin sodium, USP, packaged in bottles of 100 (NDC 0093-1712-01) and 1000 (NDC 0093-1712-10) tablets.

Source: Warfarin Sodium (Warfarin Sodium) — US FDA prescribing information, 2025-06-17, DailyMed. Summarised and shortened; the full label governs. Iranian registration, indications and labelling may differ.