Anticoagulant medicines are the main form of treatment for deep vein thrombosis. Anticoagulants affect the way blood clots in the body.

Medication Choices

Anticoagulants

Anticoagulants can prevent new clots from forming and prevent existing clots from getting larger; however, they do not break up or dissolve existing blood clots.

Anticoagulants are used to:

• Treat existing deep vein thrombosis.
• Prevent a blood clot that can develop after some types of surgery.
• Prevent blood clots in people who are at high risk (such as those who have had previous clots).

Anticoagulants that are used to prevent and treat deep vein thrombosis include:

• Heparin. The two types of heparin are:
  • Low-molecular-weight heparin (LMWH). This type can be self-injected at home, which is more convenient.
  • Unfractionated heparin (UH). This type is given through a vein (IV) or through an injection under the skin. UH typically requires regular monitoring and is usually given in the hospital.
• Warfarin (such as Coumadin), an oral anticoagulant.

Heparin acts immediately, while warfarin takes several days to become effective. Heparin will be discontinued when warfarin is at a therapeutic level.

Low-molecular-weight heparin (LMWH) and unfractionated heparin (UH) are both effective at treating deep vein thrombosis. LMWH is typically preferred over UH, because LMWH can be given at home and typically does not require monitoring with blood tests.

The ideal length of time to continue treatment with an oral anticoagulant varies and is still being researched. In general, treatment of a blood clot with oral anticoagulant medicines will continue for about 3 to 6 months. The length of time will vary based on your own health.

• If you have a short-term risk of deep vein thrombosis because of surgery, treatment with oral anticoagulant medicines usually lasts a shorter period of time.⁸
• If you have recurrent blood clots or continuing risk factors (such as cancer), anticoagulant treatment usually continues as long as those risk factors are present, which could be for the rest of your life.⁸
• If you have inherited blood-clotting disorders, you may need oral anticoagulants indefinitely.⁶

Studies show that proper anticoagulant therapy reduces the rate of recurrent blood clots from 25% to less then 5% in the first 3 months.⁹ When used to initially treat deep leg vein thrombosis, heparin reduces the risk of developing deep vein blood clots and fatal blood clots in the lungs (pulmonary embolism) by 60% to 70%.¹⁰ Some people may take low-molecular-weight heparin (LMWH) long-term instead of warfarin.

After your initial treatment with warfarin, your doctor may recommend that you take warfarin on an ongoing basis to prevent deep vein clots from recurring.²

If you take warfarin, don't suddenly change your intake of foods that are rich in vitamin K. Vitamin K can interfere with the action of anticoagulants, making it more likely that your blood will clot. For more information, see:

Anticoagulants: Vitamin K and your diet.

What To Think About

Aspirin may help prevent blood clots and reduce the risk of pulmonary embolism. But experts do not agree on how well aspirin works for preventing pulmonary embolism.

Thrombolytics are sometimes used in certain situations to treat deep vein thrombosis. But thrombolytics have a high risk of causing bleeding. They may be used if you have problems when you take heparin.

People with other illnesses such as liver or kidney problems, a recent stroke, recent surgery, inherited bleeding disorders, a bleeding ulcer, or other internal bleeding may not be able to take anticoagulants or thrombolytic medications.

Pregnant women with deep vein thrombosis should not use warfarin. Only unfractionated heparin or low-molecular-weight heparin should be given.