Which drug promotes fibrinolysis?

Urokinase promotes fibrinolysis, which is the process of breaking down fibrin in blood clots. It is a type of thrombolytic agent that works by activating plasminogen to plasmin, the enzyme responsible for digesting fibrin and dissolving clots. This mechanism is particularly valuable in treating conditions like acute myocardial infarction or pulmonary embolism, where rapid removal of a thrombus is essential to restore blood flow.

The other options play different roles in the context of coagulation and thrombosis. Warfarin is an anticoagulant that works by inhibiting vitamin K-dependent clotting factors to prevent clot formation rather than directly promoting clot breakdown. Heparin also serves as an anticoagulant, increasing the activity of antithrombin to inhibit clotting factors, thus preventing new clot formation but not promoting the dissolution of existing clots. Aspirin works by inhibiting platelet aggregation, which reduces the formation of clots but does not have a direct role in the breakdown of established fibrin structures.