Clopidogrel 💊
⚠️ Important: Clopidogrel is a prodrug that requires activation by hepatic CYP450 (especially CYP2C19).
Delayed onset of full platelet inhibition may occur (~48 hours without a loading dose).
Always consult cardiology before stopping dual antiplatelet therapy (DAPT) after PCI or ACS.
📖 About
- Clopidogrel is a thienopyridine antiplatelet agent, a selective and irreversible P2Y12 ADP receptor blocker on platelets.
- It prevents ADP-mediated platelet activation and aggregation.
- Works synergistically with aspirin in dual antiplatelet regimens.
- Always check the BNF for current dosing guidance.
⚙️ Mode of Action
- Clopidogrel is a prodrug requiring hepatic activation (CYP2C19-dependent).
- Irreversibly blocks platelet P2Y12 receptors → prevents ADP binding and downstream GP IIb/IIIa activation.
- Effect lasts for the lifespan of the platelet (~7–10 days).
- Bleeding time is prolonged.
🩺 Indications (NICE/BNF)
- Acute coronary syndrome (ACS): with aspirin for up to 12 months (NSTEMI, unstable angina, STEMI).
- Post-PCI with stenting:
- Bare-metal stent: minimum 1 month DAPT (aspirin + clopidogrel).
- Drug-eluting stent: at least 12 months DAPT (unless bleeding risk dictates otherwise).
- Secondary prevention: after ischaemic stroke, TIA, or in established peripheral arterial disease (75 mg OD).
- Aspirin intolerance: as alternative single antiplatelet therapy.
💊 Dosing – Clopidogrel (verify with BNF/datasheet)
| Indication |
Details |
| ⚡ ACS / Ischaemic Stroke / TIA – Loading |
• 300 mg PO once (UK standard)
• Sometimes 600 mg pre-PCI (per protocol)
|
| ❤️ ACS / Stroke / PAD – Maintenance |
• 75 mg PO OD lifelong (or as per local cardiology/stroke guidance)
|
🚫 Contraindications
- Active bleeding (e.g. GI haemorrhage, intracranial haemorrhage).
- Severe hepatic impairment.
- Known hypersensitivity.
- Caution in trauma, planned surgery, or thrombocytopenia.
❗ Side Effects
- GI upset: dyspepsia, diarrhoea, abdominal pain.
- Rash, pruritus, bleeding (major bleeding risk ~1%).
- Rare but serious: thrombotic thrombocytopenic purpura (TTP) with microangiopathic haemolysis.
- Bruising, epistaxis, prolonged bleeding time.
🔄 Interactions
- PPIs: Omeprazole and esomeprazole ↓ efficacy (avoid). Use lansoprazole or pantoprazole if gastroprotection required.
- Other anticoagulants / antiplatelets: additive bleeding risk.
- CYP2C19 inhibitors (e.g. fluoxetine, fluvoxamine): may ↓ clopidogrel activation.
📚 References
