Brief introduction to anticoagulants
Anticoagulants are chemical substances(drugs), whose main mechanism of action is to prevent the coagulation(clotting) of blood in order to facilitate circulation. Anticoagulants act mainly either by inhibiting ADP receptors on platelets; inhibiting the synthesis of thromboxane A2 etc. Examples of anticoagulants include: warfarin, coumarin,clopidogrel(inihibits ADP receptors).
Since NSAIDS also act to inhibit the synthesis of thromboxane A2, the concomitant introduction of an NSAID might pose the threat of profuse bleeding. This explains why aspirin(an antiplatelet) is not given together with anticoagulants.