Clopidogrel is an antiplatelet medication used to reduce the risk of disease and stroke in those at high risk, It is also used together with aspirin in heart attacks..  It is taken orally. Onset of action of 75 mg is about 2 hours and lasts for 5 days. A loading dose of 300 mg has immediate action.

Medical uses

Clopidogrel is used to prevent heart attack and stroke in people who are at high risk of these events, including those with a history of myocardial infarction and other forms of acute coronary syndrome, stroke, and those with peripheral artery disease.
Treatment with clopidogrel or a related drug is recommended by the American Heart Association and the American College of Cardiology for people who:
• Acute myocardial infarction with ST-elevation[9] including (STEMI)
• A loading dose given in advance of percutaneous coronary intervention (PCI), followed by a full year of treatment for those receiving a vascular stent
• A loading dose given in advance of fibrinolytic therapy,
• Maintenance therapy for up to 12 months in those at medium to high risk for which a noninvasive treatment strategy is chosen
• Unstable Angina, Effort angina, Non ST elevation MI
• Cerebrovascular Accident

Mechanism of action

Clopidogrel is a prodrug, which is activated in two steps, first by CYP2C19, CYP1A2 and CYP2B6, then by CYP2C19, CYP2C9, CYP2B6 and CYP3A.The active metabolite then specifically and irreversibly inhibits the P2Y subtype of ADP receptor, which is important in activation of platelets and eventual cross-linking by the protein fibrin. Platelet inhibition can be demonstrated two hours after a single dose of oral clopidogrel, but the onset of action is slow, so a loading dose of either 600 or 300 mg is administered when a rapid effect is needed.