What Are Anticoagulants and Antiplatelet Agents?

Updated:May 16,2017

Anticoagulants and antiplatelet agents are medicines that reduce blood clotting in an artery, a vein or the heart. Blood clots can block the blood flow to your heart muscle and cause a heart attack. They can also block blood flow to your brain, causing a stroke.

What should I know about anticoagulants?

Anticoagulants (or sometimes known as “blood thinners”) are medicines that delay the clotting of blood. Examples are heparin, warfarin, dabigitran, apixaban, and rivoraxaban. 

Anticoagulants make it harder for clots to form or keep existing clots from growing in your heart, veins or arteries. Treatment should be managed by your healthcare provider.

  • Follow your doctor’s (or other healthcare provider’s) instructions.
  • If you take warfarin or heparin, have regular blood tests so your doctor can tell how the medicine is working.
    • The test for people on warfarin is called a prothrombin time (PT) or International Normalized Ratio (INR) test.
    • The test for persons on heparin is called an activated partial thromboplastin time  (aPTT) test.  
  • Never take aspirin with anticoagulants unless your doctor tells you to.
  • You must tell other healthcare providers that you’re taking anticoagulants.
  • Always check with your doctor before taking other medicines or supplements, such as aspirin, vitamins, cold medicine, pain medicine, sleeping pills or antibiotics. These can affect the way anticoagulants work by strengthening or weakening them.
    • Let your doctor know if you have been started on any new medications that might interfere with the action of warfarin.
  • Discuss your diet with your healthcare providers. Foods rich in Vitamin K can reduce the effectiveness of warfarin. Vitamin K is found in leafy, green vegetables, fish, liver, lentils, soybeans, and some vegetable oils. 
  • Tell your family that you take anticoagulant medicine and carry your emergency medical ID card with you.

Could anticoagulants cause problems?

If you do as your doctor tells you, there probably won’t be problems. But you must tell your doctor right away if:

  • Your urine turns red or dark brown. This could be a sign of urinary tract bleeding.
  • Your stools turn red, dark brown or black. This could be a sign of intestinal bleeding.
  • You bleed more than normal when you have your period.
  • Your gums bleed.
  • You have a very bad headache or stomach pain that doesn’t go away.
  • You get sick or feel weak, faint or dizzy.
  • You think you’re pregnant.
  • You often find bruises or blood blisters.
  • You have an accident of any kind.

What should I know about antiplatelet agents?

Antiplatelet medicines keep blood clots from forming by preventing blood platelets from sticking together.

Many heart attack and stroke patients – and people seeking to avoid these events – are treated with two types of antiplatelet agents to prevent blood clotting; aspirin and a P2Y12 inhibitor.  This is called dual antiplatelet therapy (DAPT).

Almost everyone with coronary artery disease, including those who have had a heart attack, stent, or CABG, are treated with aspirin for the rest of their lives.

P2Y12 inhibitors are usually prescribed for months or years in addition to the aspirin therapy.  You may be prescribed one of three of these medications -- clopidogrel, prasugrel, or ticagrelor.  Prasugrel should not be prescribed if you have had a stroke or a transient ischemic attack (TIA). Which one of these your doctor prescribes will be based on what he or she feels is best for you, based on your risk of blood clots and bleeding.

Do I need to wear an emergency medical ID?

Yes, always keep it with you. Wear it – on your person or keep it in your purse or wallet. It needs to include:

  • The name of the drugs you’re taking.
  • Your name, phone number and address.
  • The name, address and phone number of your doctor.
How can I learn more?
  1. Call 1-800-AHA-USA1 (1-800-242-8721), or visit heart.org to learn more about heart disease and stroke.
  2. Sign up to get Heart Insight, a free magazine for heart patients and their families, at heartinsight.org.
  3. Connect with others sharing similar journeys with heart disease and stroke by joining our Support Network at heart.org/supportnetwork.
We have many other fact sheets to help you make healthier choices to reduce your risk, manage disease or care for a loved one. Visit heart.org/answersbyheart to learn more.

Do you have questions or comments for your doctor or nurse?

Take a few minutes to write your own questions for the next time you see your healthcare provider. For example:

What kind of aspirin should I take, and what is the right dose for me?

©2017, American Heart Association


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