Ticagrelor differs from clopidogrel and prasugrel in two important properties. Which best describes these differences?

• A Ticagrelor is a prodrug requiring CYP2C19 activation; it binds P2Y12 irreversibly like clopidogrel
• B Ticagrelor is an active drug (no hepatic bioactivation required) that binds P2Y12 reversibly at an allosteric site distinct from the ADP binding site ✓
• C Ticagrelor is an irreversible P2Y1 antagonist with a longer duration of action than clopidogrel
• D Ticagrelor inhibits both P2Y12 and PAR-1 (thrombin receptor), providing dual antiplatelet activity

Explanation

Ticagrelor belongs to the cyclopentyl-triazolo-pyrimidine class and is an active drug that does not require hepatic bioactivation, unlike clopidogrel and prasugrel (both thienopyridine prodrugs requiring CYP2C19). Ticagrelor binds to a distinct allosteric site on the P2Y12 receptor, not the ADP binding site itself, and the binding is reversible (unlike the irreversible binding of clopidogrel's active metabolite). This reversibility allows faster platelet function recovery after drug discontinuation, which is important in urgent surgery. Its unique side effects include dyspnoea (possibly related to adenosine accumulation, as ticagrelor also inhibits equilibrative nucleoside transporter ENT1) and ventricular pauses.

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

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Written and medically reviewed by the StethoPrep medical team.