From the Guidelines
The half-life of aspirin is approximately 15 to 20 minutes, as reported in the most recent and highest quality study 1. This rapid clearance is due to the body's ability to quickly break down aspirin. The clinical effects of aspirin, however, can extend beyond its half-life, particularly in its use for cardiovascular protection. Key factors that can influence aspirin's half-life include:
- Dose: Higher doses are broken down more quickly
- Age: Older adults may experience a longer half-life
- Liver function: Impaired liver function can lead to a longer half-life
- Concurrent medications: Certain medications can interact with aspirin and affect its half-life It's essential to consider these factors when prescribing aspirin, especially in patients with comorbidities or those taking multiple medications. The anti-platelet effects of aspirin can persist for several days due to its irreversible inhibition of platelets, as noted in 1. However, the most critical aspect of aspirin's pharmacokinetics is its rapid absorption and peak plasma levels, which can be achieved within 30 to 40 minutes after ingestion, as reported in 1.
From the Research
Half-Life of Aspirin
The half-life of aspirin (acetylsalicylic acid) is reported to be approximately 15-20 minutes 2, 3, 4.
- The absorption half-life of aspirin ranges from 5 to 16 minutes, depending on the formulation and rate of gastric emptying 4.
- The serum half-life of aspirin is approximately 20 minutes, after which it is hydrolyzed to salicylic acid 4.
- The terminal half-lives of aspirin and its metabolite, salicylic acid, are 0.4 and 2.1 hours, respectively 5.
- The half-life of aspirin in whole blood is relatively rapid, with a mean of 22.2 minutes, and exhibits a significant negative correlation with hematocrit 6.
Factors Affecting Half-Life
- The concentration of erythrocytes can modulate the survival of aspirin in human blood, with higher concentrations of erythrocytes resulting in a shorter half-life 6.
- The presence of human serum albumin can also affect the hydrolysis rate of aspirin, with normal levels of albumin resulting in a half-life similar to that measured in whole blood 6.
- The use of diisopropyl fluorophosphate can inhibit the rate of aspirin hydrolysis in washed red blood cells and whole blood 6.