Aspirin and Antiplatelet Medications (cont.)

Unlike the treatment of patients with advanced atherosclerosis, aspirin use among healthy subjects (for example, individuals with no prior heart attacks or strokes) is more controversial. In the U.S. Physicians' Health Study (a study comparing 325 mg of aspirin every other day to placebo among more than 20,000 healthy male doctors), there were fewer heart attacks among aspirin users as compared to placebo users. However, the overall rate of death from heart disease was no different between aspirin users and men on placebo. Furthermore, there is insufficient data to evaluate the benefit of aspirin among healthy women.

Therefore, the potential benefits of long-term aspirin in healthy subjects may not justify the small risks of serious side effects of aspirin, including bleeding from ulcers and blood vessels in the brain. Healthy individuals should discuss long-term therapy with aspirin with their doctors before they start taking aspirin. Most doctors recommend aspirin in healthy subjects who have one or more risk factors for developing atherosclerosis.

What are the latest recommendations on the use of aspirin in the primary prevention of cardiovascular disease?

As described below, the recommendations for the secondary prevention (in people who already have had a heart attack or stroke) of future attacks are more compelling.

In 2009, the U.S. Preventive Services Task Force (USPSTF) has come up with slightly modified recommendations for the primary prevention of cardiovascular disease using aspirin. Based on their review of the published data:

  • They encourage the use of aspirin in men between 45-79 years of age and women between 55-79.

  • In individuals older than 80, the treatment with aspirin was associated with more bleeding episodes which outweigh the protective benefits.

  • In men younger than 45 and women younger than 55, the benefits of aspirin seemed to too insignificant to warrant routine use for the prevention of cardiovascular disease.

What is the optimal dose of aspirin for treating and preventing heart attacks and strokes?

An ideal dose of aspirin is one that maximizes its benefits but minimizes side effects. However, the ideal dose of aspirin for primary or secondary prevention of ischemic strokes and heart attacks has not been established firmly.

In situations where an immediate antiplatelet effect is needed (for example, in the treatment of acute heart attacks, ischemic strokes, and unstable angina) aspirin at moderate doses (160–325 mg/day) will produce rapid and immediate antiplatelet effects. In the ISIS-2 trial, a dose of 160 mg/day given within 24 hours of the onset of symptoms of heart attack was shown to decrease deaths due to heart attacks by 23%. Therefore, this is the dose recommended for acute heart attacks and unstable angina.

At lower doses, such as 75 mg/d, the antiplatelet effect of aspirin can be achieved in several days instead of minutes. Since the risk of serious bleeding from aspirin is lower at lower doses, 75 mg/d is an appropriate dose for long-term primary and secondary prevention. Even though aspirin at doses as low as 40 mg/d has been shown to have anti-platelet effects, there is insufficient and inconclusive data to show that such low doses are effective in preventing heart attacks and ischemic strokes.

There also is no evidence that higher doses of aspirin, such as 1000 mg/day or higher, is more effective than lower doses. Some studies even suggest that higher doses may not be as effective as lower doses. Since the side effects of aspirin are more frequent with higher doses, doctors generally do not recommend higher doses for long-term use.

The USPSTF also looked into the optimal dose of aspirin for primary preventive purposes in 2009. They concluded that the low doses of 75-100mg daily were as effective as higher doses in preventing vascular disease and less associated with bleeding complications.

Who should be taking aspirin to prevent heart attacks and strokes?

Even though aspirin is available without a doctor's prescription and has been used safely for many years by patients for fever and pain, patients should NOT take aspirin on a long-term basis without consulting with their doctor.

Aspirin prevents blood clots from forming inside arteries affected by atherosclerosis, but aspirin does not prevent atherosclerosis. Other measures (losing excess weight, controlling high blood pressure and diabetes, lowering LDL cholesterol, increasing HDL cholesterol, and stopping cigarette smoking) are necessary to prevent atherosclerosis.

Most doctors now recommend low doses of aspirin long-term for patients with advanced atherosclerosis for secondary prevention purposes. Such patients include those with:

  • prior heart attacks

  • prior strokes

  • exertional and unstable angina

  • TIAs (transient ischemic attack, mini-stroke)

  • peripheral vascular disease (poor artery blood flow to the legs)

  • vascular procedures such as PTCA and CABG

Doctors also consider low dose aspirin in patients at risk for atherosclerosis because they:

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