aspirin

Last edited 05/2021 and last reviewed 11/2023

Aspirin is used as an:

• analgesic
• antipyretic
• antirheumatic
• antiplatelet agent

It has an anti-inflammatory action and is useful in minor trauma.

Secondary prevention of cardiovascular disease:

• low-dose aspirin (75mg daily) is recommended indefinitely for long-term secondary prevention following a myocardial infarction (MI), and in people with symptomatic peripheral arterial disease (PAD).

Primary prevention of cardiovascular disease:

• for primary prevention of cardiovascular (CV) events, low-dose aspirin (75mg daily) should be considered for all patients over the age of 50 at high risk of coronary heart disease (CHD) (10-year CHD risk of 15% or more) provided hypertension is controlled.

Notes:

• secondary prevention of cardiovascular disease:
  • a systematic review and meta-analysis of 195 randomised controlled trials (RCTs) (n=144,051) conducted by the Antithrombotic Trialists' Collaboration (2) provides evidence for the benefits of antiplatelet drugs, primarily aspirin, in preventing CV events in high-risk patients
    • serious CV events (non-fatal MI, non-fatal stroke or vascular death) occurred in 10.7% of patients on antiplatelet therapy compared with 13.2% of patients in the control groups (P<0.0001)
      • significant relative risk reductions were shown for individual primary outcome events (non-fatal MI 34%; non-fatal stroke 25%; vascular death 15%; all P<0.0001)
      • the study authors concluded aspirin (or another oral antiplatelet drug) is protective in most types of patient at increased risk of occlusive vascular events, including those with an acute myocardial infarction or ischaemic stroke, unstable or stable angina, previous myocardial infarction, stroke or cerebral ischaemia, peripheral arterial disease, or atrial fibrillation. Low dose aspirin (75-150 mg daily) is an effective antiplatelet regimen for long term use, but in acute settings an initial loading dose of at least 150 mg aspirin may be required
  • a smaller meta-analysis revealed (3):
    • treatment of 1000 patients for an average of 33 months would prevent 33 cardiovascular events, 12 nonfatal MIs, 25 nonfatal strokes, and 14 deaths, and cause 9 major bleeding events
• dose of aspirin in the prevention of cardiovascular disease:
  • an open-label pragmatic trial found no differences in cardiovascular events (event rate 7.28% vs 7.51%; HR 1.02; 95% CI 0.91 to 1.14) or major bleeding (0.63% vs 0.60%; HR 1.18; 95% CI, 0.79 to 1.77) in patients with CVD assigned to 81 mg or 325 mg of aspirin daily, respectively (4)
    • there was substantial dose switching to 81 mg of daily aspirin and no significant differences in cardiovascular events or major bleeding between patients assigned to 81 mg and those assigned to 325 mg of aspirin daily

Reference:

• (1) MeReC Bulletin 2005; 15(6):21-4.
• (2) Antithrombotic Trialists' Collaboration. Collaborative meta-analysis of randomised trials of antiplatelet therapy for prevention of death, myocardial infarction, and stroke in high risk patients. BMJ 2002;324:71-86
• (3) Berger JS et al. Low-dose aspirin in patients with stable cardiovascular disease: a meta-analysis. Am J Med. 2008 Jan;121(1):43-9.
• (4) Jones WS et al. Comparative Effectiveness of Aspirin Dosing in Cardiovascular Disease.May 15, 2021 DOI: 10.1056/NEJMoa2102137