When should Acetylsalicylic acid (aspirin) therapy be initiated?

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Last updated: March 27, 2025View editorial policy

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From the Guidelines

Aspirin therapy should be initiated after consulting with a healthcare provider, as it's not appropriate for everyone, and the decision to start should be based on individual risk assessment, considering the benefits and harms of therapy, as recommended by the most recent guidelines 1. When considering the initiation of aspirin therapy, several factors must be taken into account, including the patient's age, cardiovascular risk factors, and bleeding risk.

  • For primary prevention of cardiovascular disease, aspirin (typically 81-100 mg daily) may be recommended for adults aged 40-70 who have elevated cardiovascular risk but low bleeding risk, as suggested by earlier studies 1.
  • For secondary prevention in those with established cardiovascular disease, aspirin (usually 81 mg daily) is typically recommended indefinitely, as supported by evidence from various trials 1.
  • If a patient is experiencing a suspected heart attack, chewing a 325 mg aspirin tablet immediately can be lifesaving while awaiting emergency services, due to its rapid action in inhibiting platelet aggregation 1. Aspirin works by inhibiting platelets from forming clots, which can prevent heart attacks and strokes, but this same mechanism increases bleeding risk.
  • Common side effects include stomach irritation and bleeding, so taking it with food may help, and the use of enteric-coated or buffered preparations does not clearly reduce adverse gastrointestinal effects 1.
  • Aspirin should be avoided in people with bleeding disorders, certain gastrointestinal conditions, aspirin allergies, or those taking certain medications, as these conditions may increase the risk of serious bleeding 1. Never start aspirin therapy without medical guidance, as the benefits must outweigh the risks for your specific situation, and individual preferences and risk aversions concerning myocardial infarction, stroke, and gastrointestinal bleeding should be discussed with a healthcare provider 1.

From the Research

Aspirin Therapy Initiation

  • Aspirin therapy should be initiated in patients with acute coronary syndrome (ACS) as part of dual antiplatelet therapy (DAPT) consisting of aspirin and a P2Y12 inhibitor 2.
  • The American College of Cardiology/American Heart Association (ACC/AHA) recommends aspirin plus a P2Y12 inhibitor for at least 12 months for patients with ACS 2.
  • In primary prevention, aspirin should be considered for men and women whose 10-year cardiovascular risk is > 6% and ≥ 10%, respectively 3.
  • Aspirin therapy can be initiated in patients with a history of myocardial infarction, transient ischemic attacks, occlusive stroke, unstable and stable angina, percutaneous coronary interventions, and coronary artery bypass graft 3.

Dosing Considerations

  • The optimal dose of aspirin remains uncertain, but a range of 75-160 mg/day is commonly used for secondary prevention of myocardial infarction, stroke, and vascular death 4.
  • Daily doses of 75-325 mg aspirin are sufficient for long-term treatment and prevention of cardiovascular disease 5.
  • A loading dose of 162.5 to 325 mg is necessary to achieve a rapid clinical antithrombotic effect in acute myocardial infarction and during acute occlusive stroke 5.

Patient Characteristics

  • Patients at higher risk of bleeding, such as those 65 years old or older, with low body weight, diabetes, or prior bleeding, may require shorter duration of DAPT (3-6 months) 2.
  • Patients with a history of stroke or transient ischemic attack should avoid prasugrel due to an increased risk of cerebrovascular events 2.
  • Patients older than 75 years or who weigh less than 60 kg should also avoid prasugrel 2.

References

Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

Research

Aspirin in cardiovascular disorders. What is the optimum dose?

American journal of cardiovascular drugs : drugs, devices, and other interventions, 2004

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

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