Examples

Generic Name	Brand Name
low-molecular-weight heparin, LMWH	Fragmin, Innohep, Lovenox
unfractionated heparin (UH)
warfarin	Coumadin

How It Works

Anticoagulants work by increasing the time it takes a blood clot to form. This also prevents a clot from getting bigger.

Why It Is Used

In people who have had pulmonary embolism, anticoagulants are used to prevent additional blood clots from forming and causing another episode of pulmonary embolism.

How Well It Works

Anticoagulants are effective in preventing pulmonary embolism and deep vein thrombosis.¹

Typically, warfarin is given for at least 3 to 6 months after pulmonary embolism to reduce the risk of having another blood clot.

Treatment with anticoagulants may continue throughout your life if your risk of having another pulmonary embolism remains high. Talk with your doctor about whether continuing low-dose warfarin after your initial treatment might be right for you.

Side Effects

Anticoagulants can increase the risk of bleeding or bruising, including:

• Bleeding inside the brain (cerebral hemorrhage).
• Bleeding in the stomach and intestines if ulcers or gastritis is present.

In addition, warfarin can occasionally cause a serious skin rash and can interact with many other medications. Heparin can decrease platelet counts, leading to serious bleeding problems.

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

What To Think About

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

• Blood in the urine.
• Red stools, or black stools that look like tar.
• Unusual bleeding from the nose or gums or if you are spitting up blood.
• Abnormally long menstrual periods.
• Unusual bruising or small red or purple spots on the skin (petechiae).

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.

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.

When taking anticoagulants, you will need to be monitored closely using frequent and regular tests to check how the medication is affecting your blood. Although taking too much anticoagulant can dramatically increase your risk of serious bleeding, taking too little anticoagulant medication fails to prevent the formation of another deep vein thrombosis or another pulmonary embolism.

Eat a balanced diet. Don't suddenly change your intake of vitamin K–rich foods, such as broccoli, brussels sprouts, cabbage, asparagus, lettuce, spinach, and some vegetable juices. It is most important to maintain a consistent level of vitamin K foods in your diet. Vitamin K can interfere with the action of warfarin, making it more likely that your blood will clot.

Avoid excessive use of alcohol. If you drink, do so only in moderation. Alcohol may decrease the effect of warfarin. Don't use tobacco of any kind.

Avoid activities that have a high risk for injury, such as skiing, football, or other contact sports. If you are taking warfarin, an injury could result in excessive bleeding. Wear a seat belt anytime you are traveling in a car.

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Citations

1. Kearon C, Hirsh K (2003). Pulmonary embolism section of Venous thromboembolism. In DC Dale, DD Federman, eds., Scientific American Medicine, vol. 1 part 1, chap. 18. New York: WebMD.