Asprin works by inhibiting platlet function/ anti-thrombosis/ decreases vasoconstriction. 

Pharmacokinetic: Also, is highly bound to plasma (99%), so displaces Warfarin, leading to increased levels of Warfarin that is active. Therefore increases bleeding if taken with Warfarin.

Also: decreases renal excretion of Penicillin and Methotrexate by competing for the transport mechanism.