antithrombotic antithrombotic an antithrombotic agent is a drug that reduces the formation of blood clots (thrombi). antithrombotics can be used therapeutically for prevention (primary prevention, secondary prevention) or treatment of a dangerous blood clot (acute thrombus). in the u.s., the american college of chest physicians publishes clinical guidelines for clinicians for the use of these drugs to treat and prevent a variety of diseases. processes different antithrombotics affect different blood clotting processes: antiplatelet drugs limit the migration or aggregation of platelets. anticoagulants limit the ability of the blood to clot. thrombolytic drugs act to dissolve clots after they have formed.