Should aspirin (acetylsalicylic acid) be administered sublingually or orally in the context of a myocardial infarction?

Aspirin Administration Route in Myocardial Infarction

Aspirin should be administered orally (chewed, non-enteric coated) rather than sublingually in the context of myocardial infarction. There is no evidence supporting sublingual administration, and all major guidelines specifically recommend oral administration with chewing to maximize absorption speed.

Recommended Administration Method

The optimal approach is to administer 162-325 mg of non-enteric coated aspirin that should be chewed before swallowing. 1, 2 This method achieves the fastest onset of antiplatelet effect compared to other oral formulations.

Loading Dose Specifications

• Initial dose: 162-325 mg orally 1, 2

  • The 162 mg dose has Level of Evidence A support 1, 2
  • The 325 mg dose has Level of Evidence C support 1
  • European guidelines recommend 150-325 mg orally 1

• Formulation matters critically: Non-enteric coated aspirin must be used for the loading dose 1, 2

  • Enteric-coated formulations delay absorption and should never be used acutely 1, 2

Why Chewing is Superior

Chewing aspirin tablets accelerates absorption and shortens the time to antiplatelet effect compared to swallowing whole tablets. 3

• Chewed aspirin achieves 50% platelet inhibition in 5.0 ± 0.6 minutes 3
• Swallowed whole tablets require 12.0 ± 2.3 minutes for the same effect 3
• Maximum platelet inhibition occurs approximately 30 minutes after chewing 162 mg 4

Alternative Routes When Oral Administration is Not Possible

If the patient cannot take oral medication:

• Intravenous aspirin (where available in Europe): 250-500 mg IV 1

  • Note: IV aspirin is not available in the United States 1

• Rectal administration: 325 mg 1

There is no guideline recommendation or evidence supporting sublingual aspirin administration in myocardial infarction. 1

Pharmacokinetic Rationale

The oral chewed route is preferred because:

• Acetylsalicylic acid is rapidly absorbed with mean Tmax of 27 ± 8 minutes when chewed 4
• Plasma concentrations sufficient for maximal platelet inhibition are achieved within 30 minutes 4
• Chewing achieves approximately 1,000 ng/ml plasma concentration needed for 50% thromboxane B2 inhibition 3

Important Caveat in Sympathetic Excitement

In patients with high sympathetic tone (such as during acute MI), aspirin absorption may be delayed. 5

• Platelet aggregation inhibition may not begin until 45 minutes after administration 5
• This delay reinforces the importance of early administration and adequate dosing 5
• The 162 mg dose represents a true minimum; doubling this dose may be preferable in acute MI 4

Maintenance Dosing After Loading

Following the initial loading dose:

• Continue with 75-100 mg daily (non-enteric coated preferred) 1, 2
• This maintenance dose should be continued indefinitely 1, 2
• The lower maintenance dose minimizes bleeding risk while maintaining efficacy 1, 2

Common Pitfalls to Avoid

• Never use enteric-coated aspirin for acute loading - this delays onset of action by hours 1, 2
• Do not assume sublingual administration is equivalent - there is zero evidence supporting this route 1
• Do not delay administration - aspirin should be given immediately upon suspicion of MI, even before definitive diagnosis 2
• Do not underdose - while 162 mg is the minimum effective dose, 325 mg may provide more reliable platelet inhibition in the acute setting 1, 4