Clopidogrel, sold under the trade name Plavix among others, is an antiplatelet medication used to reduce the risk of heart disease and stroke in those at high risk. It is also used together with aspirin in heart attacks and following the placement of a coronary artery stent (dual antiplatelet therapy). It is taken by mouth. Onset of effects is about two hours and lasts for five days.Common side effects include headache, nausea, easy bruising, itching, and heartburn. More severe side effects include bleeding and thrombotic thrombocytopenic purpura. While there is no evidence of harm from use during pregnancy, such use has not been well studied. Clopidogrel is in the thienopyridine-class of antiplatelets. It works by irreversibly inhibiting a receptor called P2Y12 on platelets.Clopidogrel was patented in 1982, and approved for medical use in 1997. It is on the World Health Organization's List of Essential Medicines. In 2017, it was the 40th most commonly prescribed medication in the United States, with more than 19 million prescriptions.