What is warfarin sodium (Coumadin) used for?

• Blood clot treatment for venous thrombosis, also known as deep vein thrombosis—a blood clot in the deep vein, usually in the leg.
• Blood clot treatment for pulmonary embolism, or blood clot in the lung. 
• Blood clot prevention for people with atrial fibrillation (a heart condition that causes irregular heartbeat), prosthetic (mechanical) heart valves, or people who have had a heart attack.

How does warfarin sodium (Coumadin) work?

The formation of blood clots requires the involvement of different clotting factors—these are natural substances in the body. Vitamin K is essential in the whole clotting cascade because vitamin K is needed for the body to make clotting factors and prevent bleeding. Warfarin works by blocking the formation of vitamin-K-dependent clotting factors; thus, it reduces the body’s ability to form blood clotting. As a result, warfarin treatment prevents blood clots from forming and keeps the existing blood clots from getting bigger. 

What is the suggested dosing for warfarin sodium (Coumadin)?

Warfarin dose is unique to the person who takes it. Initially, the usual prescribed dose of warfarin is 2 mg or 5 mg, taken by mouth in the evening. The INR (international normalized ratio) test is a blood test that is done regularly, especially at the beginning of warfarin treatment, to determine the appropriate dose of warfarin. If the INR is too high, bleeding may occur. If the INR is too low, blood clotting occurs.
No renal adjustment is recommended.

The following events may warrant a dose reduction:

• weight loss
• acute illness
• smoking cessation

The following events may warrant a dose increase:

• weight gain
• diarrhea
• vomiting

Below is the typical dosing regimen for some disease states that require warfarin treatment.

Prevention of blood clots (thromboembolism) in adults with atrial fibrillation (A-Fib):

Initial dose: 2 mg to 5 mg by mouth once daily
Maintenance dose: 2 mg to 10 mg by mouth once daily
Target INR: 2.5 with the range of 2 to 3
Duration of therapy: indefinite 

Prevention of blood clots (thromboembolism) in adults after a stroke:

Initial dose: 2 mg to 5 mg by mouth once daily
Maintenance dose: 2 mg to 10 mg by mouth once daily
Target INR: 2.5 with the range of 2 to 3
Duration of therapy: Indefinite

Prevention of blood clots (thromboembolism) in adults after a heart attack (myocardial infarction):

Initial dose: 2 mg to 5 mg by mouth once daily
Maintenance dose: 2 mg to 10 mg by mouth once daily
Target INR: 2 to 3
Duration of therapy: Minimum three months after the heart attack

Prevention or treatment of deep vein thrombosis (DVT) in adults:

Initial dose: 2 mg to 5 mg by mouth once daily
Maintenance dose: 2 mg to 10 mg by mouth once daily
Target INR: 2.5 with the range of 2 to 3
Duration of therapy:

• For DVT or PE (pulmonary embolism) with known / reversible cause or risk factor: 3 months.
• For DVT or PE (pulmonary embolism) without known / reversible cause or risk factor: at three months, the duration of treatment will be evaluated to determine the necessity to continue anticoagulant therapy.
• Two episodes of DVT or PE (pulmonary embolism) without known / reversible cause or risk factor: indefinite.

Prevention of blood clots (thromboembolism) in adults with prosthetic heart valves:

Initial dose: 2 mg to 5 mg by mouth once daily
Maintenance dose: 2 mg to 10 mg by mouth once daily
Depending on the type of prosthetic heart valve, the target INR is either 2.5 with the range of 2 to 3, or 3 with the range of 2.5 to 3.5. 

Treatment of blood clots in the lungs (pulmonary embolism - PE) in adults: 

Initial dose: 2 mg to 5 mg by mouth once daily
Maintenance dose: 2 mg to 10 mg by mouth once daily
Target INR: 2.5 with the range of 2 to 3
Duration of therapy: indefinite 

Usual pediatric dose for blood clot disorder:

The following warfarin dose is recommended by ACCP (American College of Chest Physicians) to prevent blood clots for neonates and children:
Initial dose (if baseline INR is 1 to 1.3): 0.2 mg/kg orally
Dose adjustments should be made after that to maintain an INR between 2 and 3.