Health Library Anticoagulants for Atrial FibrillationFrom Healthwise

Anticoagulant medicines help prevent the formation of blood clots by increasing the time it takes a blood clot to form. This also prevents an existing clot from getting larger.

Anticoagulants are used to lower the risk of stroke in people who have atrial fibrillation. Your doctor may recommend anticoagulants based on your risk factors and on whether you can take anticoagulants safely. Anything that increases your risk for a disease or problem is called a risk factor. The more risk factors you have, the greater your risk of stroke.

Risk factors for stroke include:

• Previous transient ischemic attack or stroke.
• Artificial heart valve.
• Rheumatic mitral valve disease.
• High blood pressure.
• Heart failure.
• Lower than normal ejection fraction.
• Age 75 years or older.
• Diabetes.
• Coronary artery disease.

Anticoagulants reduce the risk of stroke in anyone with atrial fibrillation. Even after your heart rhythm is under control, you may still take warfarin. Some people go in and out of atrial fibrillation without even knowing it. Taking warfarin can lower your chances of having a blood clot or a stroke.

The use of anticoagulants is recommended for at least 3 weeks before and 1 to 3 months after cardioversion.

Should I take anticoagulants to prevent stroke?

Anticoagulants have been shown to reduce the risk of stroke in people who have atrial fibrillation.

Anticoagulants may cause:

• Easy bruising.
• Bleeding anywhere in the body.
• Skin rash.

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

If you are taking anticoagulants, notify your doctor immediately if you have:

• Unusual bruising or red or purple spots on the skin.
• Unusual bleeding from the nose or gums or if you are spitting up blood.
• Blood in your urine.
• Red stools or stools that look like black tar.
• Blood or material that looks like coffee grounds in vomit.
• Abnormally long menstrual periods.

Safety tips when taking anticoagulants may be helpful, such as taking your medicines at the same time each day and watching for signs of bleeding.

It is important that you know what to do if you miss a dose of anticoagulant.

Atrial fibrillation caused by rheumatic heart disease usually requires a higher dosage of anticoagulant.

You will need to have your blood tested periodically to check your prothrombin time (clotting time) while taking anticoagulant medicines. Your clotting time is usually reported in INR (which stands for international normalized ratio). Most people should have an INR between 2 and 3 to have the best protection against stroke. Anticoagulant therapy requires regular monitoring because high levels of anticoagulants increase the risk of bleeding, while levels that are too low increase the risk of stroke and heart attack.

Women with atrial fibrillation who are pregnant or plan to become pregnant should talk with their doctor about the potential benefits and risks of taking anticoagulants. In particular, women should not begin taking warfarin (such as Coumadin) during pregnancy and should not become pregnant while taking it because it can cause birth defects. Check with your doctor immediately if you are taking this medicine and think you may be pregnant. Use of some anticoagulants, such as heparin, may complicate pregnancy and childbirth and can increase the risk of developing osteoporosis or thrombocytopenia if taken over the long term. Other anticoagulant medicines are available for pregnant women.

Anticoagulants interact with other medicines and some foods. Don't suddenly change your intake of vitamin K–rich foods, such as broccoli, cabbage, asparagus, lettuce, and spinach.

Alcohol can change the way an anticoagulant works. Do not drink alcohol while taking anticoagulant medicines. Also, talk to your doctor or pharmacist about possible interactions that anticoagulants may have with your current medicines.

To avoid bleeding, take special care when you shave and when you brush and floss your teeth:

• Use only a soft toothbrush, and floss very gently.
• Use an electric razor instead of a blade to shave.

Do not participate in contact sports or other potentially hazardous activities while taking anticoagulant medicines. Immediately report to your doctor any falls, blows to the body or head, or other injuries.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.

Author:	Robin Parks, MS	Last Updated: December 18, 2008
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine John M. Miller, MD - Electrophysiology
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