Clopidogrel is an antiplatelet drug used to reduce the risk of blood clotting in arteries and therefore reduce the risk of heart attack and stroke. The brand name of clopidogrel is Plavix. Other antiplatelet drugs are aspirin, prasugrel and ticagrelor. When there is an injury to a wall of a blood vessel, platelets get stimulated to produce chemicals which in turn attract other platelets to stick together forming a blood clot. Clopidogrel inhibits the platelets aggregation and formation of a blood clot.
Dual antiplatelet therapy (DATP), i.e. combination of aspirin and clopidogrel (or aspirin and prasugrel or ticagrelor) are routinely used for 12 months following a heart attack or PCI to reduce risk of another heart attack or stent thrombosis. It is absolutely essential not to prematurely discontinue this medication because particularly early after a stent insertion there very high risk of stent thrombosis with an ensuing large myocardial infarction. DATP can somewhat increase risk of bleeding and there are sometimes difficult decisions to be made if a patient on DATP needs an urgent surgical procedure but in general the benefits of DATP more than outweigh any potential risks.
Clopidogrel is normally well tolerated but possible side effects include bleeding, indigestion, stomach pain, black stools, nausea or vomiting, rarely neutropenia (low white blood cell count). Omeprazole, the most commonly prescribed proton pump inhibitors (PPI), used to protect stomach lining in patients with history of gastric or duodenal ulcers, reduces efficacy of clopidogrel. Patients on clopidogrel, who need a PPI, are therefore normally given lansoprazole which doesn't have this interaction.