What is the recommended loading dose of aspirin (acetylsalicylic acid) in acute ischemic stroke management?

Recommended Loading Dose of Aspirin in Acute Ischemic Stroke

In patients with acute ischemic stroke, a single loading dose of 160-325 mg of aspirin should be administered after intracranial hemorrhage is ruled out on neuroimaging studies. 1

Aspirin Loading Dose Recommendations

Standard Loading Dose

• For patients with acute ischemic stroke who were not previously on antiplatelet therapy:
  • 160 mg loading dose (minimum effective dose) 1
  • Up to 325 mg loading dose is also appropriate 1
  • Administration should occur within 24-48 hours after stroke onset 1

Special Situations

• For patients with minor ischemic stroke (NIHSS ≤3) or high-risk TIA (ABCD2 ≥4) receiving dual antiplatelet therapy:

  • Aspirin loading dose of 160-325 mg combined with clopidogrel loading dose (300-600 mg) 1
  • Should be initiated within 12-24 hours of symptom onset

• For patients with mild-moderate ischemic stroke (NIHSS ≤5) or high-risk TIA receiving aspirin plus ticagrelor:

  • Aspirin loading dose of 300-325 mg combined with ticagrelor loading dose (180 mg) 1
  • Should be initiated within 24 hours of symptom onset

• For patients with swallowing difficulties:

  • Rectal aspirin 325 mg is recommended 1
  • Alternatively, aspirin 81 mg via enteral tube 1

Administration Protocol

1. Confirm diagnosis with neuroimaging to rule out intracranial hemorrhage
2. Administer loading dose within 24-48 hours of stroke onset
3. Follow with maintenance dose of 81-325 mg daily for long-term secondary prevention 1

Important Considerations

• Aspirin should not be administered as a substitute for thrombolytic therapy in eligible patients 1
• Aspirin should be delayed until 24 hours after thrombolysis and after confirming absence of hemorrhage on follow-up imaging 2
• The primary benefit of aspirin in acute stroke is reduction in early recurrent stroke rather than treatment of the initial event 1, 3
• The loading dose achieves rapid inhibition of thromboxane biosynthesis, which is essential in the acute setting 3

Evidence Strength and Rationale

The recommendation for aspirin loading dose is supported by high-quality evidence, with a Class I, Level of Evidence A recommendation from the American Heart Association/American Stroke Association 1. The World Stroke Organization also endorses this practice as both a minimal and essential component of stroke care 1.

Early aspirin therapy has been shown to reduce mortality and improve functional outcomes by preventing early recurrent ischemic events. The International Stroke Trial demonstrated a 14% proportional reduction in mortality and fewer recurrent ischemic strokes with aspirin therapy 4.

While higher loading doses (up to 325 mg) provide rapid platelet inhibition, they may slightly increase the risk of gastrointestinal side effects. The benefit of preventing recurrent stroke outweighs this risk in the acute setting 5.