The coagulation cascade, as anticoagulants see it

The intrinsic and extrinsic arms of the coagulation cascade converge on factor X. Activated factor Xa, with factor Va, converts prothrombin (factor II) to thrombin (IIa). Thrombin converts fibrinogen to fibrin, the clot's mesh. Factors II, VII, IX and X are synthesized in the liver and require vitamin-K-dependent carboxylation to function; warfarin inhibits vitamin K epoxide reductase (VKORC1), so new factors emerge inactive. An effect that takes days as existing factors decay, monitored by the INR. Apixaban, rivaroxaban and edoxaban inhibit factor Xa directly; dabigatran inhibits thrombin directly, immediate, predictable, unmonitored effects.