P2Y12 receptor
Summary
P2Y12 is a Gi-protein-coupled ADP receptor on platelet surfaces that promotes platelet activation and aggregation upon binding ADP. It is the pharmacologic target of antiplatelet drugs like clopidogrel, prasugrel, and ticagrelor used in ACS and stent management. Inhibition reduces platelet aggregation by preventing GPIIb/IIIa activation.
Detail
The P2Y12 receptor is a purinergic Gi-coupled receptor expressed on platelet membranes. When ADP (released from dense granules upon initial platelet activation) binds P2Y12, it inhibits adenylyl cyclase, lowering cAMP levels. Reduced cAMP decreases inhibition of platelet activation pathways, leading to sustained activation of the GPIIb/IIIa receptor complex, which binds fibrinogen and promotes platelet cross-linking and stable aggregate formation. P2Y12 activation also amplifies the initial platelet response triggered by thromboxane A2 and other agonists, stabilizing the platelet plug.
Clinically, P2Y12 inhibitors are a cornerstone of antiplatelet therapy. Thienopyridines (clopidogrel, prasugrel) are prodrugs requiring hepatic activation (clopidogrel via CYP2C19, subject to genetic polymorphisms causing variable efficacy) that irreversibly bind P2Y12. Ticagrelor and cangrelor are non-thienopyridine, reversible P2Y12 inhibitors with more predictable onset and offset. These drugs are used in acute coronary syndrome (ACS), percutaneous coronary intervention (PCI) with stent placement, and secondary prevention of stroke/TIA, often in dual antiplatelet therapy (DAPT) combined with aspirin.
Key exam points: Clopidogrel resistance due to CYP2C19 poor metabolizer status; prasugrel contraindicated in patients with prior stroke/TIA due to bleeding risk; ticagrelor can cause dyspnea and requires twice-daily dosing; cangrelor is IV and used periprocedurally. Thrombotic thrombocytopenic purpura (TTP) is a rare but serious adverse effect associated with ticlopidine/clopidogrel.
Sources
- First Aid for the USMLE Step 1
- Katzung's Basic and Clinical Pharmacology
- UpToDate: Antiplatelet agents in cardiovascular disease
- Goodman & Gilman's The Pharmacological Basis of Therapeutics
Reviewed by AnkiBoss editorial — medical student review. Information here is for study reference only and is not medical advice. Spotted an error? Let us know.