Clopidogrel
Plavix · Duoplavin
Thienopyridine P2Y12 receptor inhibitor (irreversible)
Prodrug → active metabolite (CYP2C19) irreversibly blocks the platelet P2Y12 ADP receptor for the platelet lifespan.
Indications
- •ACS
- •Post-PCI/stent (DAPT with aspirin)
- •Secondary stroke/CV prevention
Dosing
| Context | Adult | Pediatric |
|---|---|---|
| Loading | 300–600 mg PO | — |
| Maintenance | 75 mg PO daily | — |
Pharmacokinetics
Onset 2–6 h (faster with load). Irreversible — platelet effect lasts 5–7 days. CYP2C19 poor metabolizers → reduced efficacy.
Side effects
- !Bleeding
- !Reduced efficacy in CYP2C19 poor metabolizers
- !TTP (rare)
Contraindications
- ×Active bleeding
- ×Recent neuraxial without appropriate hold
Clinical pearls
- ★ASRA neuraxial: hold 5–7 days before neuraxial block/catheter removal.
- ★Do NOT stop DAPT prematurely after recent stent — stent thrombosis is often fatal; coordinate with cardiology.
- ★CYP2C19 poor metabolizers get less effect — a reason some centers use ticagrelor/prasugrel.
Other drugs in Antiplatelets
- Aspirin
Irreversibly acetylates COX-1 → blocks thromboxane A2 for the platelet's lifespan (~7–10 days). Antiplatelet effect at low dose; analgesic/anti-inflammatory at high dose.
- Prasugrel
Prodrug → active metabolite irreversibly blocks P2Y12. More potent + more consistent than clopidogrel (not CYP2C19-limited), but more bleeding.
- Ticagrelor
Directly and REVERSIBLY inhibits P2Y12 (not a prodrug, not thienopyridine). Faster onset/offset than clopidogrel.
- Ticlopidine
Irreversibly blocks P2Y12. Largely replaced by clopidogrel due to hematologic toxicity.
- Abciximab
Fab fragment that irreversibly blocks the platelet GP IIb/IIIa receptor → prevents fibrinogen cross-linking (final common pathway of aggregation).
- Eptifibatide
Reversibly blocks GP IIb/IIIa (final common pathway of platelet aggregation). Short-acting.
- Dipyridamole
Inhibits platelet PDE (↑ cAMP) and adenosine reuptake (↑ adenosine → vasodilation). Weak antiplatelet; also a coronary vasodilator used in stress testing.
- Cilostazol
Inhibits PDE3 → ↑ cAMP → antiplatelet + arterial vasodilation. Improves claudication walking distance.
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