warfarin (Coumadin, Jantoven)

Medical Author:
Medical Editor:

GENERIC NAME: warfarin

BRAND NAME: Coumadin, Jantoven

DRUG CLASS AND MECHANISM: Warfarin is an oral anticoagulant, a drug that inhibits the clotting of blood. It prevents the formation of blood clots by reducing the production of factors by the liver that promote clotting, factors II, VII, IX, and X, and the anticoagulant proteins C and S. The production of these factors by the liver are dependent on adequate amounts of vitamin K. Warfarin reduces the production of the factors because it antagonizes vitamin K. Blood clots can occur in the veins of the lower extremities (deep venous thrombosis [DVT]), often after periods of immobility. These clots can break off and become lodged in the blood vessels of the lung (pulmonary embolism), causing shortness of breath, chest pain, and even life-threatening shock. Blood clots can also occur in the atria of the heart during atrial fibrillation and around artificial heart valves. These clots also can break off and obstruct blood vessels in the brain, causing an embolic stroke with paralysis. Warfarin is important in preventing the formation of blood clots, preventing extension of clots already formed, and minimizing the risk of embolization of blood clots to other vital organs such as the lungs and brain. The FDA approved warfarin in June 1954.

PRESCRIBED FOR: Warfarin is used in treating patients with deep vein thrombosis (DVT) to prevent extension of the clot, and to reduce the risk of pulmonary embolism. Patients with pulmonary embolism are treated with warfarin to prevent further emboli. Warfarin also is used in patients with atrial fibrillation or artificial heart valves to reduce the risk of strokes, and after a heart attack. It also is helpful in preventing blood clots from forming in certain orthopedic surgeries such as knee or hip replacements. Warfarin is used in preventing closure of coronary artery stents due to clotting.

SIDE EFFECTS: The two most serious side effects of warfarin are:

  • bleeding,
  • necrosis (gangrene) of the skin.

Bleeding can occur in any organ or tissue. Bleeding around the brain can cause severe headache and paralysis. Bleeding in the joints can cause joint pain and swelling. Bleeding in the stomach or intestines can cause weakness, fainting spells, black tarry stools, vomiting of blood, or coffee ground material. Bleeding in the kidneys can cause back pain and blood in urine.

Other side effects include:

Signs of overdose include bleeding gums, bruising, nosebleeds, heavy menstrual bleeding, and prolonged bleeding from cuts.

Medically Reviewed by a Doctor on 10/16/2015

Report Problems to the Food and Drug Administration

You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.

Pill Finder Tool

Need help identifying pills and medications?
Use the pill identifier tool on RxList.

Back to Medications Index