Antiplatelets and anticoagulants are both antithrombotic drugs. They prevent clot formation or thrombosis. They don’t break up clots. Both of them simply keep a clot from forming or stopping the growth of one. To break a clot, you need a thrombolytic like tPA or Streptokinase.
Antiplatelets, as the name implies, work by preventing platelets from clumping and forming a clot.
Anticoagulants don’t work on platelets. They do their work by inhibiting clotting factors which are part of the coagulation cascade.
In general,
-Anticoagulants are used for conditions that involve stasis. Stasis can cause blot clots (thrombosis) to form. That’s why PCDs are used for DVT prophylaxis.
-Antiplatelets are used for conditions that involve endothelial damage and platelets sticking to the injured site. For example, in the heart, ischemia and MI are usually not due to stasis but to plaque formation with coronary vessels. So you use antiplatelets.
But with atrial fibrillation, there is stasis in the heart that can cause thrombosis and send a thrombus to the brain causing a CVA, so you need anticoagulants.