A 62-year-old woman with acute inferior wall STEMI presents 90 minutes after symptom onset. She is haemodynamically stable and has been taken directly to a PCI-capable centre. Which antiplatelet agent is the preferred P2Y12 inhibitor for dual antiplatelet therapy in this setting?

Explanation

## P2Y12 Inhibitor Selection in Primary PCI for STEMI **Key Point:** Ticagrelor is the preferred P2Y12 inhibitor for acute STEMI undergoing primary PCI due to superior antiplatelet potency, faster onset, and proven mortality reduction compared to clopidogrel. ### Pharmacological Comparison of P2Y12 Inhibitors | Property | Ticagrelor | Clopidogrel | Prasugrel | |----------|-----------|-----------|----------| | **Class** | Cyclopentyladenosine | Thienopyridine | Thienopyridine | | **Onset** | 30 min | 2–4 hours | 30 min | | **Peak Effect** | 2–4 hours | 3–5 days | 30 min | | **Reversibility** | Reversible | Irreversible | Irreversible | | **Loading Dose** | 180 mg | 600 mg | 60 mg | | **Maintenance Dose** | 60 mg BD | 75 mg daily | 5–10 mg daily | | **Mortality Benefit in STEMI** | Yes (PLATO trial) | Yes | Yes (TRITON-TIMI 38) | | **Bleeding Risk** | Moderate | Moderate | Higher | | **Bradycardia Risk** | Yes (AV block) | No | No | **High-Yield:** The PLATO trial (2009) demonstrated that ticagrelor reduced cardiovascular death, MI, and stent thrombosis by 16% compared to clopidogrel in acute coronary syndromes [cite:Harrison 21e Ch 297]. ### Dual Antiplatelet Therapy (DAPT) Protocol in Primary PCI 1. **Aspirin:** 300–325 mg loading dose IV/PO immediately 2. **Ticagrelor:** 180 mg loading dose PO (or IV if unable to swallow) 3. **Maintenance:** Aspirin 75–100 mg daily + Ticagrelor 60 mg BD for ≥12 months ### Clinical Pearl **Ticagrelor is superior in acute settings** because: - Faster onset of action (30 minutes vs 2–4 hours for clopidogrel) - Reversible binding allows faster recovery if emergency surgery needed - Proven reduction in stent thrombosis in primary PCI cohorts - Superior in high-risk presentations (anterior STEMI, haemodynamic instability) ### When to Use Prasugrel Instead Prasugrel is preferred over ticagrelor in: - Patients with prior stroke/TIA (ticagrelor contraindicated) - Patients with bradycardia or AV block (ticagrelor-related) - Weight <60 kg and age ≥75 years (dose adjustment required) ### When to Use Clopidogrel Clopidogrel is acceptable when: - Ticagrelor/prasugrel contraindicated or unavailable - Chronic kidney disease (CKD stage 4–5) — reduced ticagrelor efficacy - Patient intolerance to ticagrelor (bradycardia, dyspnoea) **Warning:** Do not use clopidogrel monotherapy in acute STEMI — it is inferior to ticagrelor and prasugrel. Clopidogrel is reserved for stable CAD or when newer agents are contraindicated.