Clopidogrel

Clopidogrel is an oral antiplatelet medication in the thienopyridine class that reduces the risk of stroke, heart attack, and other vascular events by inhibiting platelet aggregation. It is commonly used in patients with acute coronary syndrome and in those who have undergone percutaneous coronary intervention, often as part of dual antiplatelet therapy with aspirin.

Clopidogrel is a prodrug that requires hepatic conversion by cytochrome P450 enzymes to an active thiol metabolite. The active form irreversibly blocks the P2Y12 ADP receptor on platelets, preventing ADP-mediated activation and aggregation. Because the drug binds irreversibly, its antiplatelet effect lasts for the life of the platelet (about 7–10 days) after a dose is given, even after plasma levels fall.

Indications include prevention of thrombotic events in patients with acute coronary syndrome (including NSTEMI and STEMI) and in patients after coronary stent placement. It is also used to reduce vascular events in individuals with established atherosclerotic disease, including prior myocardial infarction, stroke, or peripheral arterial disease. The typical maintenance dose is 75 mg once daily, with a loading dose of 300 mg (or 600 mg for certain PCI protocols) at initiation. For stroke or transient ischemic attack, 75 mg daily is commonly used.

Pharmacogenomic variability can affect clopidogrel activation; reduced CYP2C19 function may lessen its antiplatelet effect in some individuals. In such cases, alternative antiplatelet agents may be considered. Important drug interactions include increased bleeding risk with NSAIDs or anticoagulants, and potential reduction in activation with certain proton pump inhibitors.

Common adverse effects include bleeding, bruising, and gastrointestinal upset; rare but serious events include thrombotic thrombocytopenic purpura and neutropenia. Clopidogrel should be used with caution in patients with active major bleeding or significant hepatic impairment.