Ticagrelor is preferred over clopidogrel in acute coronary syndrome based on PLATO trial data. The mechanistic superiority of ticagrelor involves which property?
- A Ticagrelor is a prodrug requiring CYP2C19 activation, achieving more consistent platelet inhibition than clopidogrel
- B Ticagrelor irreversibly blocks P2Y12 receptors, similar to clopidogrel, but with higher receptor affinity
- C Ticagrelor is a direct-acting, reversible P2Y12 receptor antagonist not requiring metabolic activation, providing faster onset and consistent effect irrespective of CYP2C19 polymorphism ✓
- D Ticagrelor inhibits both P2Y12 and P2Y1 receptors simultaneously
Explanation
Clopidogrel is a prodrug requiring CYP2C19 bioactivation; CYP2C19 loss-of-function polymorphisms (notably *2 and *3 alleles, prevalent in ~30% of East Asians) result in reduced active metabolite formation and inadequate platelet inhibition ('clopidogrel resistance'), associated with worse outcomes. Ticagrelor is a cyclopentyl-triazolopyrimidine that directly and reversibly binds the P2Y12 receptor without requiring metabolic activation, bypassing CYP2C19 polymorphism entirely. Its reversibility means platelet function recovers faster when stopped. Prasugrel is also not a CYP2C19 substrate to the same degree.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
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