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Anticoagulants for Pulmonary Embolism



Generic NameBrand Name
warfarinCoumadin, Xarelto, Arixtra, Fragmin, Lovenox, Innohep

Factor Xa inhibitors

Generic NameBrand Name
rivaroxabanXarelto, Arixtra, Fragmin, Lovenox, Innohep

Factor Xa specific inhibitors (used in the hospital)

Generic NameBrand Name
fondaparinuxArixtra, Fragmin, Lovenox, Innohep

Low-molecular-weight heparins

Generic NameBrand Name
dalteparinFragmin, Lovenox, Innohep
enoxaparinFragmin, Lovenox, Innohep
tinzaparinFragmin, Lovenox, Innohep

Unfractionated heparins

Generic NameBrand Name

How It Works

Anticoagulants work by increasing the time it takes a blood clot to form. They also prevent a clot from getting bigger.

Normally, when an injury that causes bleeding occurs, the body sends out signals that cause the blood to clot at the wound. The clot naturally breaks down as the wound heals. A person who is prone to abnormal clotting has an imbalance between clot formation and clot breakdown. Anticoagulants prevent the production of certain proteins that are needed for blood to clot. Anticoagulants do not break up or dissolve existing blood clots.

Why It Is Used

In people who have had pulmonary embolism, anticoagulants are used to prevent more blood clots from forming and causing another episode of pulmonary embolism. They are used in the hospital as first treatment of a pulmonary embolism. And they also may be used at home. Treatment with anticoagulants may continue throughout your life if your risk of having another pulmonary embolism remains high.


Heparin is given as an injection. It immediately affects the clotting system in your body. It might be the first anticoagulant used to treat pulmonary embolism. You might take heparin for a few days. Then you'll likely take another anticoagulant in pill form.

  • Low-molecular-weight heparin (LMWH) as initial treatment is usually preferred because it can be given as an injection once or twice per day, and it may be given at home, which allows you to leave the hospital earlier. Blood tests are not usually needed to monitor LMWH's clotting effect.
  • Unfractionated heparin is another form that can be used. It is given in the hospital. Unfractionated heparin is usually given continuously through your vein (intravenously, or IV). But it can also be given as an injection under the skin. Frequent blood tests are used to monitor the clotting effects of this medicine.


Rivaroxaban is taken as a pill. Rivaroxaban can be started right away for treatment or right after you stop taking heparin.


Warfarin is taken as a pill. Warfarin is usually started while a person is still being treated with heparin because it takes several days for warfarin to build up to a level that's effective. When warfarin is at the right level in your blood, you stop taking heparin shots and keep taking warfarin pills.


Fondaparinux is an injected anticoagulant. It is used only in the hospital.

How Well It Works

Anticoagulants are effective in preventing pulmonary embolism and deep vein thrombosis.1, 2

Side Effects

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: Callor 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: Callor other emergency services right away if you have:

  • Trouble breathing.
  • Swelling of your face, lips, tongue, or throat.

Call your doctor if you have:

  • Hives.

Heparin: Side effects often happen at injection sites. These side effects include:

  • Pain.
  • Irritation.
  • Bruising.

Warfarin: Other side effects include:

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

What To Think About

When you take anticoagulants, you need to take extra steps to avoid bleeding problems. These steps include:

Click here to view an Actionset.Warfarin: Taking Your Medicine Safely
Click here to view an Actionset.Blood Thinners Other Than Warfarin: Taking Them Safely

Long-term use of heparin is not typically recommended. It requires one or two injections each day. And long-term use is linked with osteoporosis.

Taking medicine

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 will take heparin during your pregnancy. Heparin has not been shown to affect the fetus.


If you think you might be pregnant or plan to get pregnant: Talk with your doctor. You and your doctor will decide which medicine you will take during your pregnancy. Doctors don't know if rivaroxaban affects a fetus. This medicine might cause pregnancy-related bleeding. If you take rivaroxaban, talk to your doctor about how you can prevent pregnancy.


Do not take warfarin if you are pregnant. Warfarin can cause miscarriage or birth defects. If you are taking warfarin, talk to your doctor about how you can prevent pregnancy.

If you think you might be pregnant: Call your doctor. If you are pregnant, you will take heparin during your pregnancy.

If you plan on getting pregnant: Talk with your doctor. You and your doctor will decide which medicine you will take—warfarin or heparin—while trying to get pregnant.

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)Click here to view a form.(What is a PDF document?) to help you understand this medication.



  1. Kearon C, et al. (2012). Antithrombotic therapy for VTE disease. Chest, 141(2, Suppl): e419S–e494S.

  2. EINSTEIN-PE Investigators (2012). Oral rivaroxaban for the treatment of symptomatic pulmonary embolism. New England Journal of Medicine, 366(14): 1287–1297.


ByHealthwise Staff
Primary Medical ReviewerE. Gregory Thompson, MD - Internal Medicine
Specialist Medical ReviewerJeffrey S. Ginsberg, MD - Hematology
Last RevisedFebruary 5, 2013

eMedicineHealth Medical Reference from Healthwise

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