The PLATO trial showed ticagrelor superior to clopidogrel in ACS. Unlike clopidogrel, ticagrelor exhibits which unique pharmacological property relevant to its side effect of dyspnoea?
- A Adenosine reuptake inhibition elevating plasma adenosine levels ✓
- B Irreversible P2Y12 receptor blockade causing prolonged bleeding
- C COX-2 inhibition reducing prostacyclin synthesis
- D GPIIb/IIIa receptor antagonism
Correct answer: A. Adenosine reuptake inhibition elevating plasma adenosine levels
Explanation
Ticagrelor is a reversible P2Y12 receptor antagonist that also inhibits adenosine reuptake by red blood cells (ENT1 transporter inhibition), raising plasma adenosine levels. Adenosine stimulates pulmonary vagal fibres (A1 receptors), causing dyspnoea — the most common side effect reported in PLATO (occurring in ~14%). This dyspnoea is not bronchospasm and does not require drug discontinuation in most cases. Clopidogrel is a prodrug requiring hepatic activation and causes irreversible platelet inhibition.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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