A person at risk for a heart attack may be advised to take a ________ tablet daily.

Question

BlackTom AI · Accepted Answer

Low-dose aspirin (often 75–100 mg, commonly 81 mg) irreversibly inhibits platelet cyclooxygenase-1 (COX-1), preventing formation of thromboxane A2, a potent promoter of platelet aggregation and vasoconstriction. Because platelets have no nucleus to make new COX-1, this antiplatelet effect lasts for the platelet lifespan (~7–10 days), which reduces formation of arterial clots that can cause myocardial infarction.

1) Relevant knowledge points and concepts
- Aspirin acetylates and irreversibly inhibits COX-1 in platelets → decreases thromboxane A2 → reduces platelet aggregation.
- Low doses (≈75–100 mg/day) are sufficient for antiplatelet effect while minimizing systemic side effects.
- Platelets cannot resynthesize COX-1, so the effect persists for days.
- Nonsteroidal anti-inflammatory drugs (NSAIDs) like ibuprofen reversibly inhibit COX enzymes and do not provide the same long-lasting antiplatelet protection; some NSAIDs can even interfere with aspirin’s action.

2) Step-by-step reasoning
- Goal: reduce risk of arterial thrombosis that causes heart attacks by decreasing platelet aggregation.
- An irreversible COX-1 inhibitor at low dose selectively targets platelets without excessive anti-inflammatory dosing.
- Low-dose aspirin meets this need; ibuprofen (high or low) provides reversible COX inhibition and is not recommended for daily primary antiplatelet prophylaxis.

3) Calculations/intermediate numeric steps
- Typical prophylactic aspirin dosing: 75 mg (Europe) to 81 mg (U.S.) daily; this is below analgesic/anti-inflammatory doses (300–1000 mg) and sufficient for platelet COX-1 irreversibility.

4) Why the correct answer is correct
- Low-dose aspirin produces the desired long-lasting antiplatelet effect with the lowest effective dose, reducing myocardial infarction risk in appropriate patients.

5) Why other options are incorrect
- High-dose aspirin: unnecessary for antiplatelet effect and increases GI/bleeding risk.
- High-dose ibuprofen and low-dose ibuprofen: ibuprofen’s COX inhibition is reversible (short-lived) and does not provide reliable long-term platelet inhibition; ibuprofen can also interfere with aspirin’s binding to COX-1.

6) Conclusion
Therefore, the correct preventive recommendation is low-dose aspirin. This matches the provided answer: low-dose aspirin.

A person at risk for a heart attack may be advised to take a ________ tablet daily.单项选择题

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