Warfarin for Atrial Fibrillation
How It Works
Warfarin helps 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.
Why It Is Used
Warfarin is used to lower the risk of stroke in people who have atrial fibrillation. Your doctor may recommend warfarin based on your risk factors and on whether you can take warfarin 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.
If you are age 55 or older and have atrial fibrillation, you can find your risk of stroke using this Interactive Tool: What Is Your Risk for a Stroke if You Have Atrial Fibrillation?
Risk factors for stroke include:
Warfarin can reduce the risk of stroke in anyone who has 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.
Your doctor may have you take an anticoagulant for a few weeks after cardioversion for atrial fibrillation.
How Well It Works
Warfarin lowers the risk of stroke in people who have atrial fibrillation. But how much your risk will be lowered depends on how high your risk was to start with. Not everyone with atrial fibrillation has the same risk of stroke. It's a good idea to talk with your doctor about your risk.
You will want to weigh the benefits of reducing your risk of stroke against the risks of taking warfarin. Warfarin works well to prevent stroke. But warfarin also raises the risk of bleeding. Each year 1 to 2 out of 100 people who take warfarin will have a problem with severe bleeding, and 98 to 99 will not.1 But this is an average risk. Your own risk may be higher or lower than average, based on your own health.
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:
Call your doctor right away if:
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: Call
Call your doctor if you have:
Other side effects of warfarin 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 warfarin, you need to take extra steps to avoid bleeding problems.
For more information, see:
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 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.
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.
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