What are the primary indications of aspirin (acetylsalicylic acid)?

Primary Indications of Aspirin

Aspirin has several primary indications, with the strongest evidence supporting its use for secondary prevention of cardiovascular events in patients with established cardiovascular disease, while its role in primary prevention has become more restricted due to bleeding risks outweighing benefits in many populations. 1

Secondary Prevention of Cardiovascular Disease

• Established cardiovascular disease: Aspirin (75-100 mg daily) is strongly recommended for patients with:

  • Previous myocardial infarction
  • Previous stroke
  • Peripheral vascular disease
  • Established coronary heart disease 1, 2

• Acute coronary syndromes: Initial loading dose of 160-325 mg, followed by 75-150 mg daily maintenance dose 1

• Benefits in secondary prevention:

  • Reduces risk of coronary heart disease by 28%
  • Reduces risk of serious vascular events by approximately 25%
  • Reduces nonfatal MI by 26%
  • Reduces stroke by 25%
  • Reduces all-cause mortality by 13% 1

Primary Prevention of Cardiovascular Disease

• Current recommendations are more restrictive than previous guidelines due to recent evidence showing bleeding risks may outweigh cardiovascular benefits in many individuals 1

• May be considered in select individuals aged 40-59 years with:

  • High 10-year ASCVD risk (≥10%)
  • Low bleeding risk
  • Shared decision-making required 1

• Not recommended for primary prevention in:

  • Adults aged 60 years or older (regardless of cardiovascular risk)
  • Individuals with low ASCVD risk
  • Patients with increased bleeding risk 1

Dosing Recommendations

• Secondary prevention: 75-150 mg daily is as effective as higher doses 1, 3
• Primary prevention (when appropriate): 75-100 mg daily 1
• Acute MI: Initial loading dose of 160-325 mg, followed by 75-150 mg daily 1

Risk Assessment Before Initiating Therapy

Cardiovascular Risk Assessment

• Calculate 10-year ASCVD risk using validated calculator
• Consider age, sex, diabetes, cholesterol levels, blood pressure, family history, smoking status 4, 1

Bleeding Risk Assessment

• Evaluate for bleeding risk factors:
  • Age >70 years
  • History of GI bleeding/ulcers
  • Concurrent anticoagulant or NSAID use
  • Uncontrolled hypertension
  • Renal disease
  • Anemia
  • Thrombocytopenia
  • Coagulopathy
  • Chronic kidney disease 1

Contraindications

• Absolute contraindications:

  • Active peptic ulcer disease
  • History of aspirin allergy
  • Severe liver disease
  • Bleeding disorders
  • Age under 21 years (risk of Reye syndrome) 1

• Relative contraindications:

  • History of GI bleeding/ulcers
  • Age >70 years
  • Concurrent anticoagulant or NSAID use
  • Uncontrolled hypertension 1

Monitoring Considerations

• Monitor for signs of bleeding (gastrointestinal, intracranial)
• Assess for cardiovascular events
• Avoid abrupt discontinuation in patients with established cardiovascular disease as this increases risk of cardiovascular events 1

Important Caveats

• The benefit-risk ratio is most favorable in high-risk patients for secondary prevention
• Aspirin increases the risk of major bleeding by 29-48%
• Major GI bleeding occurs in 2-4 per 1,000 middle-aged individuals and 4-12 per 1,000 older individuals over 5 years
• Hemorrhagic stroke risk increases by 0-2 per 1,000 persons over 5 years 4, 1
• Approximately 10-20% of patients may exhibit "aspirin resistance" where they continue to experience cardiovascular events despite therapy 5