Unfractionated heparin for deep vein thrombosis

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Unfractionated heparin for deep vein thrombosis


Generic Name
unfractionated heparin

How It Works

Normally, when an injury that causes bleeding occurs, the body sends out signals that cause blood to clot at the wound, and the clot naturally breaks down as the wound heals. A person prone to abnormal clotting has an imbalance between clot formation and clot breakdown.

Anticoagulant medicines prevent new clots from forming and prevent existing clots from growing (extending) by stopping the production of certain proteins that are needed for blood to clot. They do not break up or dissolve existing blood clots.

Why It Is Used

Heparin can be used to prevent and initially treat a deep vein thrombosis.

When used for prevention, heparin will be given by injection just under the skin a few hours before surgery and 2 to 3 times a day for several days after surgery.

When used for treatment, heparin is given through the vein (intravenously, or IV) in a continuous infusion or by injection just under the skin two times each day. Also, blood tests will be done at least one time a day to monitor the effect of the medicine.

When heparin is given through an IV, it can be turned off quickly. This method is safe for people who might bleed or need procedures done in an emergency.

How Well It Works

Heparin can be used to treat or prevent a deep vein thrombosis. When used for treatment, heparin prevents new blood clots from forming and prevents existing clots from getting larger. This allows the normal body systems to dissolve the clots that are already formed.

Heparin reduces the chance that a blood clot will get larger. This reduces the risk of getting a blood clot in the lung (pulmonary embolism).

Unfractionated heparin works well to treat and prevent deep vein thrombosis. But there are times when a doctor might use low-molecular-weight heparin, especially in people who just had orthopedic surgery.

Side Effects

Bleeding is the most common side effect of heparin. This may include:

  • Bleeding from an undiagnosed ulcer or growth in the digestive system.
  • Serious bleeding in other areas because of an injury or fall.
  • Serious bleeding that can occur in the brain, resulting in death (rare).

If you are taking an anticoagulant and you see signs of bleeding, notify your doctor immediately.

Other possible side effects include:

  • Rarely, a blood disorder called thrombocytopenia.
  • Localized irritation, pain, or bruising at the location where it is given.
  • Bone loss, which may occur as a side effect of heparin use that lasts 1 month or more. Heparin is rarely given for longer than 3 to 7 days. But longer treatment is sometimes required when a person cannot take warfarin (such as during pregnancy).

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

Call your doctor immediately if you are bleeding and it does not stop when you apply pressure.

Unfractionated heparin (UH) is given through a vein (intravenously, or IV) or injected under the skin.

Pregnant women can take unfractionated and low-molecular-weight heparin but not warfarin, an oral anticoagulant.

You will need to take precautions to avoid bleeding problems while you are taking heparin. These precautions include:

People with active stomach ulcers or severe liver or kidney disease probably should not take anticoagulants.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.


By Healthwise Staff
Primary Medical Reviewer E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer Jeffrey S. Ginsberg, MD, MD - Hematology
Last Revised February 26, 2010

This information does not replace the advice of a doctor. Healthwise, Incorporated disclaims any warranty or liability for your use of this information.