Examples

Nonfractionated heparin

Low-molecular-weight heparins

Coumarin

Direct thrombin inhibitors (only used in the hospital)

How It Works

Anticoagulants are often called "blood thinners," although they don't really thin blood. They decrease the blood's ability to clot.

Why It Is Used

Anticoagulants are given during unstable angina or a heart attack because they can prevent clots from becoming larger and blocking coronary arteries. They are often given with other anticlotting medicines to help prevent or reduce heart muscle damage.

Also, anticoagulants are used to prevent blood clots from forming in the heart during or after a heart attack. The risk of blood clots forming in the heart chambers increases with an irregular heartbeat or heart failure. If the clot enters the bloodstream and lodges in a blood vessel, it can cause a stroke or a pulmonary embolism.

Anticoagulants also may be given after angioplasty to help reduce the risk of clot formation and subsequent artery closure.

How Well It Works

Anticoagulants reduce the risk of stroke and recurrent heart attack. They may lower the risk of heart attack in people with unstable angina or those who have recently had angioplasty.

Although anticoagulants can lower your risk of a heart attack, using them also slightly raises your risk of severe bleeding.

Side Effects

Anticoagulants can cause bleeding problems. Check with your doctor if any of the following occur:

• Increased bruising or tiny red or purple spots on the skin
• Bleeding that is difficult to stop, especially nosebleeds that happen often
• Bleeding gums
• Blood in your urine
• Coughing up blood
• Abnormally long or heavy menstrual bleeding
• Black stools, stools that look like tar, bloody stools, or constipation
• Joint pain, stiffness, or swelling
• Persistent or severe headache, backache, or neck ache
• Toes (and also possibly abdomen, breasts, and other fatty tissue areas) that turn purple or blue. If this side effect occurs, call your doctor immediately.

Other side effects may indicate that you are allergic to the medicine. Talk to your doctor if you have any of the following:

• Changes in the skin color of the face or puffiness or swelling of the eyelids or around the eyes
• Tightness in the chest, difficulty breathing, and/or wheezing
• Skin rash, hives, and/or itching

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

What To Think About

Direct thrombin inhibitors, such as bivalirudin, are used only in the hospital.

The low-molecular-weight heparins (such as enoxaparin) are favored over regular heparin because they are given only 1 or 2 times per day and do not require frequent blood tests to monitor the effects of the medicine. If you cannot take heparin, your doctor may give you fondaparinux (Arixtra).¹

It is very important to follow your doctor's specific instructions about when and how often to take anticoagulants.

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.

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.

You will need regular blood tests to check the effect of the drug on your blood-clotting ability.

Carry identification stating that you are using an anticoagulant.

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

Citations

1. OASIS-5 Investigators (2006). Comparison of fondaparinux and enoxaparin in acute coronary syndromes. New England Journal of Medicine, 354(14): 1464–1476.