Argatroban is an anticoagulant that is a direct thrombin inhibitor. Argatroban was approved in 2000 for prophylaxis or treatment of thrombosis in patients with heparin-induced thrombocytopenia (HIT). Argatroban is a direct thrombin inhibitor that reversibly binds to the thrombin active site. Argatroban exerts its anticoagulant effects by inhibiting thrombin-catalyzed or -induced reactions, including fibrin formation; activation of coagulation factors V, VIII, and XIII; activation of protein C; and platelet aggregation. Argatroban inhibits thrombin with an inhibition constant (Ki) of 0.04 M.