Clopidogrel

Clopidogrel is an anti-platelet drug used to reduce platelet aggregation and inhibit thrombus formation. It belongs to the thienopyridine drug class alongside prasugrel and ticlopidine.

Mechanism of action

Clopidogrel is a prodrug which is metabolized by the liver into its active form. The active form specifically and irreversibly binds to and inhibits the P2Y₁₂ ADP receptor. This inhibits platelet activation and fibrin cross-linking.

Indications

Clopidogrel may be used for the prevention of atherothrombotic events in the following circumstances:

• Percutaneous coronary intervention
• Transient ischaemic attack
• Minor ischaemic stroke
• Secondary prevention of transient ischaemic attack (in patients without atrial fibrillation)
• Secondary prevention of ischaemic stroke (in patients without atrial fibrillation)
• Peripheral arterial disease or within 35 days of myocardial infarction
• Acute coronary syndrome without ST-segment elevation
• Acute myocardial infarction with ST-segment elevation
• Atrial fibrillation and at least one risk factor for a vascular event and for whom warfarin is unsuitable

Clopidogrel is often given in combination with aspirin (see the link for further details). Concurrent use of aspirin with clopidogrel does increase the risk of bleeding.

Side effects

Common

• Diarrhoea
• Abdominal pain
• Haemorrhage
• Skin reactions e.g. urticaria

Rare but serious

• Pancytopenia
• Thrombocytopenic purpura
• Agranulocytosis

Contraindications

• Pregnancy
• Breastfeeding
• Pathological bleeding
• Severe hepatic impairment (caution in moderate impairment)
• Hypersensitivity reactions to other thienopyridines e.g. prasugrel.