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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 then 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
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 medicines are working.
Two types of heparin are
available for treatment of deep vein thrombosis.
Unfractionated heparin is given in the hospital. Low-molecular-weight heparin (LMWH) can be self-injected at home, which
usually is more convenient.
You might take heparin for a few days. Then you will likely take another anticoagulant as a pill for at least 3 months. Some people may take
low-molecular-weight heparin long-term.
How Well It Works
Low-molecular-weight heparin can be
used to treat or prevent a deep vein thrombosis.1 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
All medicines have side effects. But many people don't feel the side effects, or they are able to deal with them. Ask your pharmacist about the side effects of each medicine you take. Side effects are also listed in the information that comes with your medicine.
Here are some important things to think about:
- Usually the benefits of the medicine are more important than any minor side effects.
- Side effects may go away after you take the medicine for a while.
- If side effects still bother you and you wonder if you should keep taking the medicine, call your doctor. He or she may be able to lower your dose or change your medicine. Do not suddenly quit taking your medicine unless your doctor tells you to.
Bleeding. Call911or other emergency services right away if:
- You cough up blood.
- You vomit blood or what looks like coffee grounds.
- You pass maroon or very bloody stools.
- You have a sudden, severe headache that is different from past headaches. (It may be a sign of bleeding in the brain.)
Call your doctor right away if you have unusual bleeding:
- You have new bruises or blood spots under your skin.
- You have a nosebleed that doesn't stop quickly.
- Your gums bleed when you brush your teeth.
- You have blood in your urine.
- Your stools are black and look like tar or have streaks of blood.
- You have heavy period bleeding or vaginal bleeding when you are not having your period.
If you are injured, apply pressure to stop the bleeding. Realize that it
will take longer than you are used to for the bleeding to stop. If you can't get the bleeding to stop, call your doctor.
Allergic reaction. Call911or other emergency services right away if you have:
Call your doctor if you have:
Injection sites. Side effects often happen at injection sites. These side effects include:
Reference for a full list of side effects. (Drug Reference is not available in
What To Think About
If you take heparin, you need to take extra steps to avoid bleeding problems.
For more information, see:
- Blood Thinners Other Than Warfarin: Taking Them Safely
Long-term use of heparin typically is not
recommended. It requires one or two injections each day. And long-term use is linked with
Medicine is one of the many tools your doctor has to treat a health problem. Taking medicine as your doctor suggests will improve your health and may prevent future problems. If you don't take your medicines properly, you may be putting your health (and perhaps your life) at risk.
There are many reasons why people have trouble taking their medicine. But in most cases, there is something you can do. For suggestions on how to work around common problems, see the topic Taking Medicines as Prescribed.
Advice for women
If you are pregnant, you can take heparin during your pregnancy. Heparin has not been shown to affect the fetus.
For more information, see Pregnancy and the Increased Risk of Developing Blood Clots.
Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor if you are having problems. It's also a good idea to know your test results and keep a list of the medicines you take.
Complete the new medication information form (PDF)(What is a PDF document?) to help you understand this medication.
Antithrombotic drugs (2011). Treatment Guidelines From The Medical Letter, 9(110): 61–66.
|Primary Medical Reviewer||E. Gregory Thompson, MD - Internal Medicine|
|Specialist Medical Reviewer||Jeffrey S. Ginsberg, MD - Hematology|
|Last Revised||February 5, 2013|