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Conditions Expert Dr. Otis Brawley Chief Medical Officer,
American Cancer Society

Expert answer

Dear Mary:

Aspirin is an old drug with lots of uses. It was noted more than 2,000 years ago that chewing the bark of the willow tree was therapeutic for headache, some musculoskeletal pains and fever. The compound responsible for these effects was isolated more than a century ago, turned into a pill and named aspirin. Aspirin was the first of a class of drugs known as nonsteroidal anti-inflammatories, or NSAIDs. Today, NSAIDs are some of the most commonly used drugs in medicine.

After aspirin had been in use for more than 70 years, studies showed that it could reduce the risk of cardiovascular disease. We continue to learn about these compounds. We now know that most of the other NSAIDs do not reduce the risk of cardiovascular disease, and some actually increase it. More recently, studies also have shown that aspirin and several other NSAIDs may reduce the risk of colon polyps and colon cancer.

Your question is important, as it has been estimated that 5% of people have some difficulty taking aspirin or other NSAIDs. These reactions are categorized as pseudo-allergic or allergic. Pseudo-allergic reactions are nonimmunologic reactions related to the person having an alteration in the biochemical pathway through which the NSAID is normally metabolized or handled after it is ingested. True allergic reactions are due to the immune system rejecting the drug. Both reactions can be acquired, meaning someone can have no difficulty with NSAIDs for years and then all of a sudden have a reaction.

The person with a pseudo-allergic reaction tends to have the reaction with a number of NSAIDs, whereas those with true allergic reactions tend to be sensitive to one specific NSAID. Some patients also have a reaction to a high dose of an NSAID but not to a lower dose of the same drug.

The pseudo-allergic and true allergic reactions can be a combination of drug-induced asthma, runny and stuffy nose, itching or swelling. Some people have severe swelling of the throat and upper airway that can lead to suffocation in very severe reactions. Patients with a history of nasal polyps are at especially high risk of NSAID allergy.

The cardiovascular effects of aspirin are due to its ability to decrease the effectiveness of platelets in the blood. This decreases the blood's ability to clot. Today, aspirin is commonly prescribed to reduce the risk of vascular problems in patients who have had:

Aspirin therapy decreases the risk of a subsequent cardiovascular event in this population by up to 20%. Several well-designed clinical trials have also established the net benefits of giving an aspirin to a person who is actively having a heart attack. It can decrease the amount of heart damage and cut the risk of death from the heart attack.

There has been debate about the use of low-dose or baby aspirin (81 mg daily) or whole adult aspirin (325 mg daily) for disease prevention. The prevailing evidence is that there is no difference in efficacy or side effects in doses ranging from 81 mg to 325 mg per day.

Some prescribe aspirin to people who have not had a cardiovascular event but are at high risk of cardiovascular disease because of diabetes, obesity, hypertension or smoking. The net benefit is clear among those with a history of cardiovascular disease but is less clear for this latter population. We use the term "net benefit" as it is clear that there are disadvantages to aspirin therapy. It causes some people to have stomach bleeding or even hemorrhagic stroke.

Aspirin or NSAID desensitization is successful in some patients. This can allow for a daily prophylactic aspirin, or for patients with rheumatologic conditions to regularly take aspirin or other NSAIDs. This procedure involves starting with a low dose of the NSAID and progressively giving larger doses over time. It should be done under the supervision of a physician experienced in this procedure.

Patients who need cardiovascular prevention who cannot be desensitized to aspirin may be candidates for therapy with the non-NSAID clopidogrel (Plavix). It, too, inhibits platelet activity and is sometimes used with aspirin.

Acetaminophen (Tylenol) is not an NSAID. It is usually well tolerated by those with a history of NSAID reactions. Acetaminophen can be used for fever control and treatments of some types of pain. It is not useful in the prevention of cardiovascular disease.