Examples

Generic Name	Brand Name
heparin
warfarin	Coumadin

Warfarin is taken in pill form.

Heparin can be given through a vein (intravenously) or by injection into fatty tissue (subcutaneously).

How It Works

Although anticoagulants are often called blood thinners, they do not really thin blood. Warfarin prevents the production of certain proteins that are necessary for blood to clot. Heparin and newer low-molecular-weight heparins interfere with the complex process of blood clot formation. Heparin and warfarin prevent new clots from forming and may prevent existing clots from getting larger. They do not break up clots.

Why It Is Used

These medicines are given only after it is certain that a person is not having a hemorrhagic stroke, which is caused by bleeding in the brain. Anticoagulants should only be used when a blood clot is suspected of causing the stroke or transient ischemic attack (TIA).

Treatment with heparin followed by warfarin is often recommended for people whose TIA or stroke was likely caused by a clot formed in the heart. Heparin often is used first (up to 2 days after the stroke) because it can be given quickly into a vein (intravenously), and it has an immediate effect on clotting. Warfarin is used long-term after heparin use is ended.

Heparin may be used if a person is having repeated TIAs or when TIA symptoms seem to be getting worse. This indicates that a blood clot may be getting bigger or that a plaque is unstable, and quick-acting anticoagulants are needed.

Most people with atrial fibrillation should take warfarin to lower their risk for stroke. One exception is people younger than 65 who have atrial fibrillation without any other risk factors for stroke.

People with active stomach ulcers, severe liver or kidney disease, or a history of falls probably should not take an anticoagulant.

How Well It Works

Anticoagulants are effective at preventing the formation of clots in people who have specific heart problems—such as atrial fibrillation—that make clot formation more likely. Warfarin has been shown to greatly reduce the risk of TIA and stroke in people who have atrial fibrillation.

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

Anticoagulants are not as effective as carotid endarterectomy surgery in preventing stroke for people who have significant hardening and narrowing of the carotid arteries (more than 70% of the artery is blocked by plaque buildup).¹

Anticoagulants should not be given within 24 hours of treatment with tissue plasminogen activator (t-PA).

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:

Warfarin: Taking your medicine safely.

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

Heparin. If you take heparin, you need to:

• Prevent falls and injuries.
• Prevent medicine interactions.

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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References

Citations

1. Biller J, et al. (1998). Guidelines for carotid endarterectomy: A statement for healthcare professionals from a special writing group of the Stroke Council of the American Heart Association. Circulation, 97(5): 501–509.