Anticoagulants for heart attack and unstable angina


Unfractionated heparin

Generic Name Brand Name
heparin Heparin

Low-molecular-weight heparins

Generic Name Brand Name
dalteparin Fragmin
enoxaparin Lovenox
tinzaparin Innohep


Generic Name Brand Name
warfarin Coumadin

Direct thrombin inhibitors (only used in the hospital)

Generic Name Brand Name
bivalirudin Angiomax
fondaparinux Arixtra
lepirudin Refludan

How It Works

Anticoagulants are often called "blood thinners," although they don't really thin blood. They decrease the blood's ability to clot.

Why It Is Used

Anticoagulants are given during unstable angina or a heart attack because they can prevent clots from becoming larger and blocking coronary arteries. They are often given with other anticlotting medicines to help prevent or reduce heart muscle damage.

Also, anticoagulants are used to prevent blood clots from forming in the heart during or after a heart attack. The risk of blood clots forming in the heart chambers increases with an irregular heartbeat or heart failure. If the clot enters the bloodstream and lodges in a blood vessel, it can cause a stroke or a pulmonary embolism.

Anticoagulants also may be given after angioplasty to help reduce the risk of clot formation and subsequent artery closure.

How Well It Works

Anticoagulants reduce the risk of stroke and recurrent heart attack. They may lower the risk of heart attack in people with unstable angina or those who have recently had angioplasty.

Although anticoagulants can lower your risk of a heart attack, using them also slightly raises your risk of severe bleeding.

Side Effects

Bleeding is the most common side effect of anticoagulants.

Know the signs of bleeding

Call 911 if:

  • You cough up blood.
  • You vomit blood or what looks like coffee grounds.
  • You pass maroon or very bloody stools.

Call your doctor right away if:

  • 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.

Warfarin may also cause a skin rash.

Heparin shots may cause irritation, pain, or bruising at the injection site.

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

What To Think About

Direct thrombin inhibitors, such as bivalirudin, are used only in the hospital.

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

Warfarin. If you take warfarin, you need to:

  • Get regular blood tests.
  • Prevent falls and injuries.
  • Eat a steady diet, and pay attention to foods that contain vitamin K.
  • Tell your doctors about all other medicines and vitamins that you take.

For more information, see:

Click here to view an Actionset. Warfarin: Taking your medicine safely.

Know what to do if you miss a dose of anticoagulant.

Heparin. If you take heparin, you need to:

Pregnancy. Do not take warfarin if you are pregnant or may become pregnant. If you are taking warfarin and think you may be pregnant, call your doctor. Warfarin can cause birth defects. If you become pregnant while taking warfarin, your doctor may recommend that you switch to a low-molecular-weight form of heparin while you are pregnant. Long-term use of these heparin formulations is not recommended, because it is associated with osteoporosis and thrombocytopenia.

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Last Updated: May 5, 2009

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