prasugrel

Prasugrel is a prodrug that requires hepatic activation (primarily via CYP3A4 and CYP2B6, less dependent on CYP2C19 than clopidogrel) to its active metabolite, which irreversibly binds the P2Y12 receptor on platelets, blocking ADP-mediated activation of the GPIIb/IIIa complex and subsequent platelet aggregation. Because activation is less dependent on CYP2C19, prasugrel has fewer issues with genetic polymorphism-related resistance compared to clopidogrel, resulting in more consistent and potent platelet inhibition.

Clinical use: Approved for reducing thrombotic cardiovascular events in patients with ACS (STEMI or NSTEMI) managed with PCI, typically combined with aspirin. TRITON-TIMI 38 trial demonstrated reduced ischemic events (including stent thrombosis) compared to clopidogrel, but with increased major bleeding, particularly in patients with prior stroke/TIA, age ≥75, or low body weight (<60 kg) — contraindicated in patients with history of stroke/TIA due to increased intracranial hemorrhage risk.

Pharmacokinetics: Onset of action faster than clopidogrel (~30 min), platelet inhibition ~2-3 times greater. Duration of platelet inhibition lasts the lifespan of the platelet (7-10 days) since binding is irreversible; typically discontinued 7 days before major surgery.

Adverse effects: Bleeding (major concern), thrombocytopenia (rare), and hypersensitivity reactions.

Comparison to other P2Y12 inhibitors: Clopidogrel (older, prodrug, more variable due to CYP2C19 polymorphisms), Ticagrelor (reversible, direct-acting, no hepatic activation required, associated with dyspnea and bradyarrhythmias).

Mechanistic classification: ADP receptor antagonist (P2Y12 inhibitor), distinct from aspirin (COX-1 inhibitor) and GPIIb/IIIa inhibitors (e.g., abciximab, eptifibatide, tirofiban).