Aspirin
- Class: Antiplatelet / NSAID
- Used for: blood clot prevention
- Say it: AS-pir-in
- Forms: tablet, chewable tablet, suppository
Aspirin acetylates COX-1 irreversibly. A platelet has no nucleus and cannot make fresh enzyme, so the effect lasts the 7-10 days until that platelet is replaced. Every other NSAID binds reversibly and wears off within hours.
Side effects
Common: indigestion, bruising, nausea
Serious: stomach bleeding, Reye's syndrome in children
Typical dose
75–100 mg once daily for prevention
300 mg chewed, not swallowed whole, in a suspected heart attack: chewing gets it absorbed in minutes.
Check yourself
Why does a single low daily dose of aspirin give a full antiplatelet effect?
- It blocks COX-1 irreversibly, and platelets cannot make new enzyme
- It has a very long half-life in the blood
- It is stored inside the platelet and released slowly
- It blocks the P2Y12 receptor for a full 24 hours
Show answer
A. It blocks COX-1 irreversibly, and platelets cannot make new enzyme
Aspirin's own half-life is only about twenty minutes. The duration comes from what it leaves behind — a permanently acetylated COX-1 enzyme inside a cell with no nucleus to build a replacement.
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