Examples

Unfractionated heparins

Low-molecular-weight heparins

Coumarins

Direct thrombin inhibitors (only used in the hospital)

How It Works

Anticoagulants are often called blood thinners, but they don't really thin blood. They work by increasing the time it takes for a blood clot to form. This prevents an existing clot from increasing in size, thereby preventing a heart attack or stroke.

Why It Is Used

Anticoagulants are often used to prevent blood clots from forming in the heart during or after a heart attack. Anticoagulants also may be given after angioplasty to help prevent a new blood clot after the procedure.

How Well It Works

Anticoagulants are effective in reducing the rate of stroke and recurrent heart attack in people who are having a heart attack. Anticoagulants may lessen the risk of heart attack in people with unstable angina or those who have recently had angioplasty with or without stenting.

Anticoagulants also reduce the risk of stroke in people who have recently had a large heart attack on the front wall of the heart.

Side Effects

Bleeding is the most common side effect of anticoagulants.

Know the signs of bleeding

Call 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

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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