Coagulants and anticoagulants are used to control blood clotting. In vitro anticoagulants like heparin, sodium oxalate and sodium citrate are used outside the body, while injectable heparin and oral coumarin and indandione derivatives like warfarin are used inside the body. Platelet aggregation inhibitors include clopidogrel, ticagrelor, ticlopidine and prasugrel which are used to prevent blood clots.