Ticagrelor differs from clopidogrel in its antiplatelet mechanism in which MOST clinically important way?

• A Ticagrelor blocks P2Y1 receptor while clopidogrel blocks P2Y12 receptor
• B Ticagrelor is a direct thrombin inhibitor in addition to P2Y12 blockade
• C Ticagrelor is a reversible P2Y12 antagonist; clopidogrel irreversibly blocks P2Y12 after prodrug activation by CYP2C19 ✓
• D Ticagrelor requires activation by CYP3A4 while clopidogrel is active as administered

Explanation

Ticagrelor is a reversible, direct-acting P2Y12 antagonist (does not require hepatic activation). Clopidogrel is an irreversible P2Y12 blocker requiring CYP2C19-mediated bioactivation to its active thiol metabolite — patients who are CYP2C19 poor metabolisers (up to 30% of Asians) have inadequate platelet inhibition with clopidogrel. Ticagrelor's reversibility means platelet function recovers within 3–5 days after stopping (vs 7–10 days for clopidogrel), which is beneficial pre-surgery. Both drugs act on P2Y12 (not P2Y1). Ticagrelor is not a thrombin inhibitor.

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

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Written and medically reviewed by the StethoPrep medical team.