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In this Article

• What is aspirin?
• What are antiplatelet agents and how do they work?
• What is dipyridamole?
• When is aspirin used for preventing and treating heart attacks and strokes?
• Treatment of heart attacks
• Treatment of exertional and unstable angina
• Treatment of ischemic strokes
• How effective is aspirin for preventing heart attacks among healthy subjects?
• What are the side effects of aspirin?
• What is aspirin allergy?
• What is the optimal dose of aspirin for treating and preventing heart attacks and strokes?
• Who should be taking aspirin to prevent heart attacks and strokes?
• Who should not be taking aspirin?
• What interactions might aspirin have with other medications?
• What can be done to reduce the risk of ulcers from long-term aspirin use?
• What are the limitations of aspirin treatment?
• What is aspirin resistance?
• What is in the future for the research on aspirin resistance?
• Aspirin and Antiplatelet Medications Index

Serious side effects of aspirin and other NSAIDs occur infrequently. However, they may occur and generally tend to be more frequent with higher doses. Therefore, it is advisable to use the lowest effective dose to minimize side effects.

The most common side effects of aspirin involve the gastrointestinal system.

Aspirin can cause:

• ulcers of the stomach and duodenum (first part of the small intestine),
  
  
• abdominal pain,
  
  
• nausea,
  
  
• gastritis (inflammation of the stomach), and
  
  
• even serious gastrointestinal bleeding from ulcers.

Occasionally, aspirin may be toxic to the liver.

Sometimes, ulcers of the stomach and bleeding occur without any abdominal pain, and the only signs of bleeding may be:

• black tarry stools,
  
  
• weakness, and
  
  
• dizziness upon standing (orthostatic hypotension).

Another serious but rare side effect of aspirin is intracranial hemorrhage (bleeding into the tissues of the brain), similar to a hemorrhagic stroke.

Aspirin can impair function of the kidney and liver, especially in patients who already have liver and kidney disease. Other side effects of aspirin include easy bruising, vertigo, ringing in the ears (tinnitus), and lightheadedness.

Serious side effects of aspirin, such as bleeding ulcers or intracranial bleeding, are rare (less than 1% of patients) among patients taking moderate doses of aspirin (for example, 325 mg/d). Serious side effects of aspirin should be even lower with low doses such as 75-160 mg/d. However, the actual incidence of serious bleeding with long-term use of low dose aspirin has not been clearly determined.

What is aspirin allergy?

Allergy to aspirin is a rare condition in which a patient can develop swelling of tissues, spasm of the airways (bronchospasm) that causes difficulty breathing, and even anaphylaxis, a life-threatening condition. Clearly, patients with a history of allergy to aspirin should not take aspirin. Since aspirin is related chemically to the other NSAIDs, patients who are allergic to the other NSAIDs, such as ibuprofen (Motrin) and naproxen (Aleve), also should not take aspirin.

What interactions might aspirin have with other medications?

Aspirin may interact with other medications and cause undesirable side effects. For example:

• Aspirin, when taken together with an anti-coagulant such as warfarin (Coumadin) or enoxaparin (Lovenox), can greatly impair the body's ability to form blood clots, resulting in excessive bleeding spontaneously, from ulcers, or related to a procedure. Therefore, patients on such combinations must be closely monitored by a doctor.
  
  
• Aspirin can raise levels of uric acid in the blood and may need to be avoided in patients with increased uric acid levels or gout.
  
  
• Aspirin can increase the effect of medications used for lowering blood sugar levels in patients with diabetes, resulting in abnormally low blood sugar levels (hypoglycemia). Blood sugar levels may need to be more closely monitored.
  
  
• Certain NSAIDs, particularly ibuprofen (Motrin, Advil), if taken just before aspirin or in multiples doses each day, can reduce the anti-platelet effects of aspirin and theoretically render aspirin less effective in preventing heart attacks and ischemic strokes. The ibuprofen molecule is believed to adhere to the COX-1 enzyme, thus keeping aspirin from reaching the enzyme.

What can be done to reduce the risk of ulcers from long-term aspirin use?

Long-term low dose aspirin use is generally safe. An estimated 10% of the patients taking long-term aspirin (75-325 mg/day) can develop ulcers. Most of these ulcers were asymptomatic (no abdominal pain or bleeding). Patients at a higher risk of developing ulcers with low dose aspirin included elderly patients age 70 years and older, and patients with H. pylori stomach infection (see below). The risk of significant ulcer bleeding from aspirin is low (approximately 1%). One can reduce the risk of bleeding by adding a daily dose of a proton pump inhibitor for example, pantoprazole (Protonix), esomeprazole (Nexium), rabeprazole (Aciphex), or lansoprazole (Prevacid, Prevacid SoluTab), and omeprazole (Prilosec, Zegerid).

Report Problems to the Food and Drug Administration You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088. Need help identifying pills and medications? Use the pill identifier tool on RxList.