Aspirin was already known as the “miracle drug” for its pain-relieving properties when researchers discovered in the early 1970s that it also offers many benefits to heart patients. Research conducted since then has confirmed that aspirin prevents first and second heart attacks, strokes and other cardiovascular events in people with cardiovascular disease (e.g., coronary artery disease or high blood pressure).

Aspirin works by inhibiting the blood’s ability to clot. It does this by interfering with the action of platelets, a component of blood that is involved in the formation of blood clots. Aspirin has also been shown to inhibit pro-inflammatory chemicals, which in turn may inhibit the development of atherosclerosis, or “hardening of the arteries.”

Because of its wide-ranging benefits, aspirin is recommended for many heart and stroke patients, including patients who have suffered from a heart attack, ischemic stroke or a kind of chest pain called angina. In addition, aspirin may be recommended for patients who have undergone coronary artery bypass surgery. In these cases, aspirin has been shown to reduce the chance of death by vascular disease. It is also recommended for victims undergoing heart attacks. Numerous studies have shown that patients who take an aspirin within 30 minutes after their heart attack begins may limit the damage of the attack. Experts recommend chewing aspirin rather than swallowing a tablet whole to achieve a faster effect.

Stroke patients, however, should take aspirin only under the advice of a physician because aspirin may aggravate certain kinds of stroke. Aspirin may increase the risk of another type of stroke (hemorrhagic) that is caused by bleeding into and around the brain, especially in women.

The decision to administer aspirin therapy as a preventive measure should be made by a physician. Various groups, including the American Heart Association, the American College of Cardiology and the United States Preventive Services Task Force have issued guidelines for the use of aspirin as a preventive measure for heart attack and stroke. In general, only patients at a reasonably elevated risk of suffering a heart attack, as judged by their coronary risk profile, are considered candidates for regular aspirin therapy. Even among these patients, however, studies have shown that aspirin therapy is probably underused, especially among women.

Although it is widely tolerated, aspirin may have serious side effects, including an increased risk of bleeding or gastrointestinal problems. It is estimated that about 30 percent of total drug-related hospitalizations are caused by aspirin and other nonsteroidal anti-inflammatory drugs (NSAIDs).

Aspirin should never take the place of medications or other treatments prescribed by a physician. People are encouraged to speak with their physician about whether aspirin would be helpful for them and, if so, what dosage the physician feels is appropriate.

For more than 100 years, aspirin has been used as a pain reliever for headaches and other minor aches and pains. According to the U.S. Food and Drug Administration (FDA), Americans consume more than 20 billion tablets a year.

More recently, aspirin has been widely studied in terms of preventing cardiovascular disease and managing the conditions of people who already have heart disease or a history of heart attack. Some of these research findings include:

In 2002, researchers concluded that aspirin can reduce the risk of a first heart attack by 32 percent and reduce the combined risk of heart attack, stroke and vascular death by 15 percent. The findings supported the American Heart Association's (AHA) position that aspirin should be recommended for all men and women whose 10-year risk of a first coronary event is 10 percent or greater.

In 2007, the AHA altered its guidelines to state that all women over the age of 65 should start a low-dose regimen of aspirin, regardless of their risk profile. It is thought that this step, in addition to other lifestyle changes, may improve the lifetime risk of heart disease in women. Previous guidelines had suggested that low-risk and healthy women did not need to take aspirin on a regular basis.

However, the AHA and the FDA strongly urge patients to discuss aspirin therapy with their physician. According to the FDA, many people mistakenly believe they can safely take aspirin every day because it is an over-the-counter medication. This misperception leads to more than 100,000 hospitalizations every year due to the overuse of aspirin and other over-the-counter pain medication.

Studies have found different dosages to be beneficial. Many studies suggest a low daily dose of aspirin (81 milligrams [mg]) to be effective in the prevention of heart attack and stroke. Other studies have used regular doses of aspirin (325 mg). Generally, there is no additional benefit in taking more than 325 mg a day, and dosages under 70 mg have been shown to be ineffective.

Aspirin can be taken orally in tablets or capsules with an enteric coating, which is gentler to the stomach. Aspirin may also be taken in the form of chewing gum or suppositories.

Patients who are taking aspirin for its heart benefits should be aware that taking ibuprofen (a type of nonsteroidal anti-inflammatory drug [NSAID]) at the same time to relieve pain may limit the effectiveness of aspirin. Although these two medications can be used together safely, patients should consult their physician about the timing of aspirin doses to ensure they receive the full benefit of both drugs.

The main pain-relieving chemical in aspirin (salicin) has been used for pain relief since the 5th century B.C. People such as the famous physician Hippocrates discovered that chewing willow bark and leaves, or using them to brew a potion, could help to relieve pain. It was not until the 1800s that researchers were able to identify salicin as the chemical responsible for the pain relief.

After struggling to find a way to offer the benefits of salicin without its stomach-burning properties, aspirin was first presented to the public in 1915. The manufacturing company was Bayer, a German company that lost its patent as part of the Versailles Treaty that ended World War I. Aspirin got the first letter of its name from the chemical used to make salicin gentler to the stomach (Acetyl chloride). The next four letters came from the plant from which the salicin was derived: Spirea ulmaria. The last two letters represent the common ending of drug names at the time: in. Aspirin is now one of the most widely used drugs around the world. No other pain killer provides the health benefits of aspirin.

Pain relief

Chemically, aspirin is known as the compound acetylsalicylic acid (ASA). It fights pain and inflammation by blocking enzymes called cyclooxygenase, or COX. When this enzyme is blocked, the body is less able to produce prostaglandins, which are chemicals that cause inflammation, swelling and pain. Blocking prostaglandins lessens the pain felt from an injury or body ache. Aspirin does not heal the underlying problem (i.e., the wound itself). 

Blood clot prevention

Certain prostaglandins also are involved in the action of platelets, which are necessary to form blood clots. Aspirin also blocks these prostaglandins. Therefore, aspirin belongs to a group of drugs called antiplatelets. These are non-habit-forming medications that prevent the formation of blood clots by decreasing the ability of the platelets to bind together (platelet aggregation). By helping to prevent blood clots, aspirin helps to prevent blockages in the arteries that can trigger a heart attack.

One type of prostaglandin, thromboxane, is known to be particularly affected by aspirin. Even small doses of aspirin completely stop its production. Research has shown that taking one baby aspirin (81 milligrams) a day for 10 days successfully reduced thromboxane levels. While the platelets were still able to “plug” a wound so the person did not bleed to death, the platelets were less “sticky” and therefore less likely to form blood clots. For up to 10 days after a person discontinued aspirin use, its effects were still obvious.

Heart disease prevention

By helping to prevent blood clots, aspirin helps maintain adequate blood flow through the arteries, thus lowering the risk of a heart attack in both men and women. Furthermore, aspirin has been found to reduce the damage of a current or past heart attack if taken either during or immediately after the attack. This is an important finding, since some studies have shown that less than 80 percent of heart attack patients receive aspirin. 

Along the same lines, aspirin may be used under a physician’s guidance to help in the treatment of certain types of chest pain, pressure or discomfort called angina. Aspirin therapy has also been shown to be beneficial for patients who are undergoing angioplasty or coronary bypass surgery or have experienced atrial fibrillation.

In general, aspirin has been recommended for patients in the following categories:

• Patients who have had a mini-stroke (transient ischemic attack) and/or ischemic strokes

Furthermore, patients who are scheduled for procedures to open blocked arteries (e.g., angioplasty, stenting) may benefit from “super aspirins,” which are given intravenously during cardiac interventional procedures. For these patients, treatment with “super aspirins” may significantly cut the risk of death or other major complications. People who cannot tolerate aspirin may be given a different antiplatelet called clopidogrel, which is also given to people undergoing catheter-based procedures. For those who can take aspirin, studies have shown that aspirin and clopidogrel, given together, have an enhanced effect in inhibiting clot formation. The aspirin/clopidogrel combination has also demonstrated benefit in individuals at risk for acute coronary events (e.g., those with unstable angina).

Though the findings are promising, aspirin is not for everyone. The best course of therapy begins with a physical examination and regular medical visits, as well as with a healthy lifestyle. Aspirin therapy works best with individuals whose blood pressure, cholesterol and weight levels are within normal ranges. Physicians will often advise patients not to take aspirin if they have certain pre-existing medical conditions. In general, the following people are usually advised against taking aspirin:

• Pregnant women, especially during the first and third trimesters. Aspirin can prolong or otherwise complicate delivery.
  
  
• People who are about to have surgery. Aspirin can promote excessive bleeding, and most surgeons request that their patients refrain from taking aspirin for several (generally 10) days before surgery.
  
  
• Children under 18 who are recovering from chickenpox or the flu. Aspirin has been linked to a rare, potentially fatal disease called Reye syndrome.
  
  
• Heavy drinkers (three or more drinks per day). Aspirin has been linked to stomach irritation, liver damage and excessive bleeding in such people.
  
  
• People with chronic intestinal problems, including ulcers, gastritis, inflammatory bowel disease (e.g., Crohn's disease, ulcerative colitis) and bleeding conditions.
  
  
• People taking certain blood thinning medication. Many patients can be safely treated with anticoagulants and low-dose aspirin.
  
  
• People with allergies to some medications, including aspirin.
  
  
• People with uncontrolled high blood pressure (hypertension).

A recent study discovered that a small percentage of people may be “resistant” to aspirin’s anti-clotting effects. These individuals (about 5 percent of the study participants) had triple the risk of heart attack and stroke. Researchers are working on methods to determine which patients are resistant to aspirin, as well as alternative medication therapy. The anti-platelet clopidogrel may be considered among these patients.

For individuals with no history or significant risk of heart disease, the evidence indicates that aspirin’s best medical benefit is limited to temporary pain relief. Such “low-risk” individuals should explore with their physician if the risks associated with taking aspirin outweigh its potential benefits.

Unless the aspirin is coated to be gentler to the stomach (enteric coated), aspirin should be taken with mild food or an antacid to reduce the risk of upset stomach. These coated tablets should not be chewed, crushed or broken unless in case of emergency (e.g., during a heart attack). However, some people’s gastrointestinal tracts cannot dissolve coated aspirin, and the aspirin will remain intact until it leaves the body in a bowel movement.

Guidelines for aspirin call for its use as soon as there is knowledge that a heart attack is under way, preferably in the first 30 minutes after its onset. However, it is important that anyone who is experiencing a heart attack call emergency services before taking aspirin. Prompt medical treatment for a heart attack is essential for survival. Cardiac patients should also be aware that ibuprofen (another type of pain killer) should not be used during a heart attack to relieve pain because it may reduce the effects of aspirin.

There are a number of side effects associated with aspirin use that have been reported by some patients. These include:

Aspirin should never be taken in place of other medications or treatments recommended by a physician. To understand whether aspirin would be helpful, people are encouraged to speak with their physician about benefits and risks.

Preparing questions in advance can help patients to have more meaningful discussions with their physicians regarding their conditions. Patients may wish to ask their doctor the following questions regarding aspirin:

1. Should I be on aspirin therapy?
   
   
2. What dosage would be best?
   
   
3. Does it matter what time of day I take the aspirin? Should I take it with food?
   
   
4. Will it affect any other medications I am taking?
   
   
5. How long will I be on aspirin therapy?
   
   
6. If I experience stomachaches, can I reduce the dosage?
   
   
7. Is there any other medication that might accomplish the same thing with fewer side effects?
   
   
8. Does the brand of aspirin matter? Should I take enteric coated or regular aspirin?
   
   
9. If I miss a day or two, am I at higher risk for a heart attack?
   
   
10. What dosage of aspirin should I chew if I am worried about a heart attack?