Ticagrelor differs from clopidogrel in which clinically important way?

• A Ticagrelor irreversibly blocks P2Y12 receptors unlike clopidogrel's reversible blockade
• B Ticagrelor blocks ADP release from platelet dense granules, unlike clopidogrel
• C Ticagrelor is a direct-acting, reversible P2Y12 antagonist not requiring hepatic bioactivation ✓
• D Ticagrelor acts via the P2Y1 receptor while clopidogrel acts via P2Y12

Explanation

Clopidogrel is a prodrug requiring CYP2C19-mediated hepatic conversion to an active thiol metabolite that irreversibly alkylates the platelet P2Y12 receptor. Ticagrelor is a cyclopentyltriazolopyrimidine that directly and reversibly binds P2Y12 without bioactivation, giving faster and more predictable onset. CYP2C19 loss-of-function polymorphism ('clopidogrel resistance') does not affect ticagrelor, making it superior in rapid ACS settings.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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