Clopidogrel is an anticoagulant that is used to help prevent blood clotting, thus reducing the risk of stroke and heart attack in patients with a high risk for these events. The drug works by inhibition of platelet aggregation through prevention of the binding of adenosine diphosphate (ADP) to its platelet receptor and subsequent ADP-meditative activation of the glycoprotein GPIIb/IIIa complex. It is important to note the effects of clopidogrel are irreversible and platelets are affected for the remainder of their lifespan. The most serious side effects are black tarry stools, blood in urine or stools, nose bleed, unusually heavy menstrual bleeding, unusual bleeding or bruising and sudden weakness.