VIEWPOINT

Aspirin chemoprophylaxis: A call to action

Many of us are already familiar with the good news that aspirin is very useful for secondary prevention of heart attacks as it decreases the risk of another myocardial infarction (MI) by 20% and the risk of dying by 15% in those of us who have had a previous cardiovascular event. Additionally, aspirin is a lifesaver in that it cuts the death rate by 23% if taken during an MI and continued for another 30 days. However, here's the really good news: Based on a meta-analysis of five major randomized clinical trials, published recently in Archives of Internal Medicine, aspirin has been shown to reduce the risk of a first MI (primary prevention as opposed to secondary prevention) by 32% and reduces the combined risk of MI, stroke, and vascular death by 15%.

Both the American Heart Association and the U.S. Preventive Services Task Force recommend that aspirin therapy be considered for individuals—including men over age 40 and women over age 50—whose 10-year risk of a first coronary event is 6%-10% or greater. According to Charles H. Hennekens, M.D., senior author of the Archives' article, "only about one-third of the estimated 62 million Americans who are at risk for heart disease—and who could potentially benefit from the appropriate use of aspirin—are on a daily aspirin regimen."

Pharmacists collectively have the potential to save thousands of lives yearly and help prevent many first-time heart attacks from occurring through the appropriate recommendation of low-dose aspirin chemoprophylaxis. Aspirin is beneficial for patients who have no previous diagnosis of cardiovascular disease but are at high risk (> 10%) of developing coronary heart disease over the next 10 years. However, there is a real downside to routinely recommending aspirin because in those with a low 10-year risk of developing coronary heart disease, the disadvantages of aspirin may exceed the benefits of chemoprevention. In a low-risk patient who would theoretically gain little from chemoprevention, the use of aspirin would be exposing the patient to an increased risk of gastrointestinal bleeding and hemorrhagic stroke.

How do you determine who would benefit from primary chemoprevention with low-dose aspirin? Factors used to estimate risk include sex, age, blood pressure, serum total cholesterol level (or low-density lipoprotein cholesterol level), high-density lipoprotein cholesterol level, diabetes mellitus, cigarette smoking, and left ventricular hypertrophy (LVH). Several easy-to-use risk assessment tools, most based on risk equations derived from the Framingham Heart Study, are available on the Internet. One popular risk calculator is available at www. med-decisions.com and is used to facilitate risk calculation. This Web site is valid for patients ages 30-75 with no previous history of cardiovascular disease living in the United States.

To calculate your patients' risks of angina, MI, or sudden death using the Framingham equations, you simply enter the data into this calculator. The information you supply is enough to accurately predict the risk of heart disease, even though other factors may contribute to an individual's risk.

At the present time, I would not recommend aspirin for primary prevention for men greater than 40 years of age or women greater than 50 years of age if the calculated risk of cardiovascular disease was under 10% for the next 10 years. Also remember that aspirin is contraindicated in bleeding disorders and in patients with hypersensitivity to salicylates. It would be best to refer patients to their own physicians to discuss aspirin chemoprophylaxis if they are chronic alcohol users (three or more drinks daily) since they are at increased risk of stomach bleeding.

Also, patients with asthma, nasal polyps, severe carditis, hemophilia, telangiectasis, or G-6-PD deficiency should leave the decision of aspirin chemoprophylaxis to their physicians. For those patients with preexisting hypoprothrombinemia and vitamin K deficiency, renal or hepatic dysfunction, and in patients concurrently receiving anticoagulants, pharmacists should not recommend low-dose aspirin chemoprotection. I would also not recommend aspirin chemoprophylaxis for patients receiving other aspirin-containing products, clopidogrel (Plavix, Bristol-Myers Squibb), or other similar medications.

I'm urging my fellow pharmacists to take an active role in recommending low-dose aspirin chemoprophylaxis to the estimated 40 million-plus Americans who are at a > 10% 10-year risk of developing cardiovascular disease. We can potentially save countless lives by taking this step.

Jack M. Rosenberg, Pharm.D., Ph.D.

The AUTHOR is professor of pharmacy practice and pharmacology, director of the International Drug Information Center, Arnold & Marie Schwartz College of Pharmacy and Health Sciences, Long Island University in Brooklyn, N.Y., and a member of Drug Topics' Editorial Advisory Board.

 

Jack Rosenberg. Aspirin chemoprophylaxis: A call to action. Drug Topics Nov. 3, 2003;147:22.