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Home / Resources / Articles / Issue 180 Item 6 Who should take a daily aspirin…and how much they should take

Issue 180 Item 6 Who should take a daily aspirin…and how much they should take

There’s confusion about who should or shouldn’t take a daily aspirin.

Most patients who’ve had a heart attack or stroke should take aspirin…to prevent a SECOND one. But should patients take aspirin to prevent a cardiovascular event even if they’ve never had a FIRST one? It’s a judgment call.

Aspirin can decrease the risk of a first heart attack. But it also increases the risk of GI bleeding and hemorrhagic stroke. Consider aspirin for patients most likely to benefit…men over 40…postmenopausal women…and younger patients with risk factors such as high cholesterol, hypertension, diabetes, smoking.

Think twice before recommending aspirin for patients at risk for bleeding due to gastric ulcers…uncontrolled hypertension…or if they are taking NSAIDs or anticoagulants. Cardiologists are debating the proper dose of aspirin.

Guidelines aren’t specific. They recommend 81 mg to 325 mg/day. But now experts are recognizing that 81 mg/day is at least as effective as higher doses…and likely safer.

Doses over 200 mg/day seem to almost double the bleeding risk. And, higher doses might actually be LESS effective than lower doses. High aspirin doses seem to inhibit prostacyclin, and lead to vasoconstriction…and possibly a paradoxical INCREASE in clotting.

Tell patients who need aspirin that 81 mg/day is usually best. Explain that a higher dose ISN’T more effective…and can increase the chance of serious side effects. Tell people that enteric-coated aspirin works just as well as non-enteric coated. But enteric coating doesn’t eliminate GI bleeding.

Keep in mind that taking 325 mg is still recommended during a heart attack…to prevent reinfarction or ischemic stroke. The higher dose is needed for a quick antiplatelet effect.

What about those with diabetes? There is growing consensus that people with diabetes mellitus are at particularly high short-term risk for the development of CHD.6,15 In fact, guidelines by the AHA and National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (Adult Treatment Panel III [ATP III]) consider patients with diabetes to have an equal risk of developing vascular events as individuals with known CHD.6,15 For this reason, the ATP III risk assessment tables do not take diabetes into account when calculating risk. The ATP III considers people with diabetes to be at such high risk that secondary preventative strategies are necessary for cholesterol lowering regardless of other risk factors.15

At this time the American Diabetes Association (ADA) recommends aspirin therapy as secondary prevention in all diabetics with known CHD and as primary prevention in some diabetics at high risk for CHD [Evidence level C, Consensus].16 Factors identified by the ADA to increase CHD risk and warrant aspirin therapy include family history of CHD, smoking, hypertension, obesity (>120% desirable weight, body-mass-index [BMI] >27.3 kg/m2 in women and >27.8 kg/m2 in men), albuminuria (micro or macro), hyperlipidemia (cholesterol > 200 mg/dL, LDL > 100 mg/dL, HDL < 45 mg/dL in men and < 55 mg/dL in women, triglycerides > 200 mg/dL), and age > 30 years.16

For years there has been debate in the medical community regarding when to use aspirin for vascular prevention and what is the best dose to use. Randomized-controlled trials and established guidelines recommend the use of once-daily aspirin in most patients with known vascular disease [Evidence level A, RCT].2,3 Primary prevention trials and expert consensus also advocate the use of aspirin in high-risk patients [Evidence level A, RCT].1,4-6 Aspirin should be used cautiously in patients with uncontrolled hypertension or in combination with NSAIDs or anticoagulants, due to an increase risk of bleeding.4,5
Based on data from recent trials, lower doses of aspirin are at least as effective as higher doses for the primary or secondary prevention of vascular events2,8 and may be associated with a lower risk of bleeding.8,9 In most cases, 81 mg of aspirin daily should be sufficient to provide maximal antiplatelet effects with minimal risk of bleeding. In acute settings (e.g., MI), a higher initial loading dose of aspirin (e.g., 325 mg) is warranted to ensure complete immediate blockade of thromboxaneA2.2 Further evaluation of aspirin in large, randomized trials is needed to better clarify the optimum dose of aspirin in different patient populations and clinical situations such as aspirin resistance.

Circulation 2002;106:388-91; JAMA 2001;285:2486-97: Diabetes Care 2003;26:S87-8.

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