Examples

A type of medicine that is similar to low-molecular-weight heparin is fondaparinux (Arixtra), which is a type of antithrombotic medication called a selective Factor Xa inhibitor.

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

Why It Is Used

Low-molecular-weight heparins can be used to treat a deep vein thrombosis. When used to either prevent or treat a blood clot, they are given by injection just under the skin once or twice each day. Unlike with other forms of anticoagulants, periodic blood tests are usually not needed to monitor how well the medications are working.

How Well It Works

Low-molecular-weight heparin can be used to treat or prevent a deep vein thrombosis. When used for treatment, low-molecular-weight heparins prevent new blood clots from forming and prevent existing clots from getting larger.

• This allows the normal body systems to dissolve the clots that are already formed.
• This also reduces the risk of pulmonary embolism.

Side Effects

Bleeding is the most common side effect of low-molecular-weight heparins. 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).
• Nosebleeds.

When heparins are given by injection under the skin, localized irritation, pain, or bruising can occur.

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

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

What To Think About

Low-molecular-weight heparins (LMWH) are often used in higher doses to treat deep vein thrombosis rather than prevent it. In most cases, LMWH is preferred over unfractionated heparin (UH) because it is effective and can be given at home. Most people can be treated with LMWH while at home, because:

• It is given as an injection only 1 to 2 times a day.
• It does not usually require blood tests to monitor its effects.

Unfractionated heparin usually requires a hospital stay because it is given as a continuous infusion, or IV, and frequent monitoring is often needed.

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

While you are taking any anticoagulant medications, changes to your lifestyle may be needed. These include:

• Avoiding certain activities.
• Avoiding certain other medications.

Low-molecular-weight heparin can be used in pregnant women.

Your doctor may not have you take LMWH if you have any of the following:

• Increased bleeding risk, such as from active ulcers
• Kidney or liver disease
• Very low or high body weight (more study is needed on the proper dosage and how it should be monitored)
• Problems with administering the drug, such as injection technique, or trouble getting the medication and related supplies

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