Oral anticoagulants for deep vein thrombosis

Examples

Generic Name	Brand Name
warfarin sodium	Coumadin

How It Works

Normally, when an injury that causes bleeding occurs, the body sends out signals that cause blood to clot at the wound, and the clot naturally breaks down as the wound heals. A person prone to abnormal clotting has an imbalance between clot formation and clot breakdown.

Anticoagulant medications prevent new clots from forming and prevent existing clots from growing by stopping the production of certain proteins that are necessary for blood to clot. They do not break up or dissolve existing blood clots.

Why It Is Used

Warfarin is used to prevent or treat deep vein thrombosis and pulmonary embolism. It can also be used for stroke prevention in some circumstances.

How Well It Works

Warfarin reduces the chance that a new blood clot will form or that an existing blood clot will get larger.

Side Effects

Bleeding is the most common side effect of warfarin. This may include:

• Bleeding from an undiagnosed ulcer or growth in the digestive system.
• Serious bleeding in other areas because of an injury or fall.

If you are taking an anticoagulant and develop signs of bleeding, notify your doctor immediately.

In rare cases, in the first few days of treatment with warfarin, the skin may develop a purple or blue rash because circulation is being affected by the drug. In addition, serious bleeding in the brain can occur (rarely), which may result in death.

Occasionally people will have nausea or stomach cramps from warfarin.

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

What To Think About

What to do if you miss a dose of anticoagulant:

• If you remember it in the same day, take the missed dose. Then go back to your regular schedule.
• If it is the next day, or almost time to take the next dose, do not take the missed dose. Do not double the dose to make up for the missed one. At your next regularly scheduled time, take your normal anticoagulant dose.
• If you miss your dose for 2 or more days, call your doctor.

Do not double the dose in any one day to make up for a missed dose. Call your doctor if you are not sure what to do if you missed a dose.

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

Blood tests are needed every few days at first to monitor the effects of warfarin and determine the correct dosage. Later on, blood tests may only be needed once per month.

A standard method of reporting the results of the lab value called prothrombin time (PT) is called an international normalized ratio (INR). This can be calculated from the PT result.

Unfractionated heparin or low-molecular-weight heparin is often used at first to treat blood clots because these medications have an immediate effect on clotting, whereas warfarin takes longer to start working.

Because warfarin slows how quickly blood clots, you will need to make several lifestyle changes when you are taking this medication. They include:

• Be aware of the effects of diet on warfarin. For example, vitamin K reverses the effects of anticoagulants, such as warfarin. Green, leafy vegetables (such as turnip and mustard greens, asparagus, spinach, collards, and kale) and some oils, such as canola and soybean oils, are usually high in vitamin K.
• Use safety precautions when you participate in activities with a risk of injury. These activities can include using sharp tools or power tools, working on ladders, or playing contact sports, where there is a risk of injury or falling and subsequent bleeding.
• Avoid some medications. Aspirin, nonsteroidal anti-inflammatory drugs such as ibuprofen (for example, Motrin), some antibiotics, certain seizure medications, and birth control pills may need to be avoided. Tell your doctor if you are taking any of these medications or any other nonprescription medications. Do not take any medications, vitamins, or minerals unless you first talk to your doctor.
• Get regular blood tests.

Call your doctor immediately if you notice a large amount of bleeding or if you cannot stop the bleeding simply by applying pressure.

It is important to take warfarin at the same time each day. Usually the best time to take your medication is in the evening before dinner.

People with active stomach ulcers or severe liver or kidney disease probably should not take anticoagulants.

Warfarin should not be taken during pregnancy.

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

Author:	Robin Parks, MS	Last Updated: January 15, 2008
Medical Review:	E. Gregory Thompson, MD - Internal Medicine Jeffrey J. Gilbertson, MD - Cardiovascular Surgery
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