Aspirin for heart attack and unstable angina


Generic Name Brand Name
aspirin Anacin, Ascriptin [aspirin and an antacid], Bayer, Bufferin

How It Works

Aspirin works quickly (within 15 minutes) to prevent the formation of blood clots, decreasing the risk for heart attack or stroke.

Generic or store brands are as effective as brand-name aspirin.

Why It Is Used

It has been well documented that aspirin reduces the risk of heart attack in people with known coronary artery disease (CAD). It is also now known that aspirin lowers the risk of having symptoms in people who have a higher risk for the disease. People who are at high risk for coronary artery disease or who already have coronary artery disease benefit the most from aspirin therapy.

You can take aspirin to help you during a heart attack. After you call 911 or other emergency services, chew 1 adult-strength (325 mg) aspirin or 2 to 4 low-dose (81 mg) aspirin if you are not allergic to aspirin and if there is no other reason that you can't take aspirin. Aspirin slows blood clotting. So a blood clot that is causing the heart attack stays smaller.

You may also take low-dose aspirin (81 mg) every day to help lower the risk of a heart attack or stroke. Low-dose aspirin may be used:

  • After a heart attack, to prevent another one.
  • By people who have coronary artery disease.
  • By people who have stable angina.
  • By people who have unstable angina.
  • After bypass surgery or angioplasty.
  • By people who have had a stroke or transient ischemic attack (TIA).
  • After surgery to prevent a stroke (carotid endarterectomy).
  • By healthy men over age 45 when the benefits of aspirin to prevent a heart attack are greater than the risk of stomach bleeding from taking daily aspirin.
  • By healthy women over age 55 when the benefits of aspirin to prevent a stroke are greater than the risk of stomach bleeding from taking daily aspirin.

If you have atrial fibrillation and cannot take or choose not to take warfarin, you may take an adult-strength aspirin (325 mg) every day to help lower the risk of a stroke.

How Well It Works

People who are at high risk for coronary artery disease or who have established coronary artery disease benefit the most from aspirin therapy.

  • Aspirin can lower the risk of a first heart attack and recurrent heart attacks.
  • Aspirin may reduce the severity of a heart attack when taken immediately after symptoms begin.
  • Aspirin may help improve the symptoms of unstable angina.
  • Aspirin may lower the risk of death caused by heart disease.

But in people with a relatively low risk of developing cardiovascular disease, the benefits of preventive aspirin therapy may be outweighed by the increased risk of bleeding problems.

Side Effects

Side effects of aspirin include:

  • Stomach inflammation (gastritis).
  • Gastrointestinal bleeding.
  • Allergic reaction.
  • Increased bruising and bleeding (hemorrhage) in the brain (rare) or other internal organs of the body.

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

What To Think About

Some doctors believe that people who have two or more risk factors for coronary artery disease should take aspirin every day. Others are concerned that long-term daily aspirin use will increase the risk of stomach problems or hemorrhagic stroke when untreated high blood pressure is present.

Expert guidelines recommend 75 mg to 162 mg daily.1 One low-dose aspirin contains 81 mg. One adult-strength aspirin contains about 325 mg. Consult your doctor before using aspirin on a regular basis.

Because aspirin reduces your blood's ability to clot, your doctor may want you to stop taking aspirin at least 5 days before surgery or before a dental procedure that may cause excessive bleeding.

If you have a high risk of stomach bleeding from taking aspirin regularly, your doctor may suggest you take a proton-pump inhibitor medicine to help prevent bleeding.

Do not substitute nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil, for example) or naproxen (such as Aleve), for aspirin. Although NSAIDS relieve pain and inflammation much like aspirin does, they may increase your risk for a heart attack or stroke.

If you need both aspirin and a pain reliever every day, talk to your doctor about what pain reliever you should take. If you take uncoated aspirin and ibuprofen at the same time, the aspirin may not work as well to prevent a heart attack. You may be able to use acetaminophen instead of ibuprofen to treat your pain. But if ibuprofen is your only option, avoid taking it during the 8 hours before and the 30 minutes after your aspirin dose.2 For example, you can take ibuprofen 30 minutes after your aspirin dose. If you take ibuprofen once in a while, it does not seem to cause problems.

Experts do not know if NSAIDs other than ibuprofen interfere with uncoated aspirin. Also, experts do not know if people who take a daily coated aspirin should be concerned about ibuprofen or other NSAIDs interacting with the aspirin. Talk to your doctor if you take these medicines every day.

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  1. Antman EM, et al. (2007). 2007 focused update of the ACC/AHA 2004 guidelines for the management of patients with ST-elevation myocardial infarction: A report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines. Circulation, 117(2): 296–329. Originally published online December 10, 2007 (doi:10.1161/circulationaha.107.188209).
  2. U.S. Food and Drug Administration (2006). Concomitant use of ibuprofen and aspirin: Potential for attenuation of the anti-platelet effect of aspirin. Food and Drug Administration Science Paper. September 8, 2006. Available online:

Last Updated: May 5, 2009

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