Aspirin, also known as acetylsalicylic acid, is a nonsteroidal anti-inflammatory drug NSAID that works by inhibiting the cyclooxygenase COX enzymes, specifically COX-1 and COX-2. These enzymes are responsible for the production of prostaglandins, which are lipid compounds that play a crucial role in mediating pain, inflammation, and fever.At the molecular level, aspirin interacts with COX enzymes through a process called acetylation. Aspirin's acetyl group CH3CO- covalently binds to a serine residue an amino acid in the active site of the COX enzyme. This binding leads to a conformational change in the enzyme's structure, which in turn blocks the access of arachidonic acid, a substrate for prostaglandin synthesis, to the active site.By inhibiting the COX enzymes, aspirin effectively reduces the production of prostaglandins, which results in decreased pain, inflammation, and fever. It is important to note that aspirin's effect on COX-1 is irreversible, meaning that the enzyme remains inactive for the lifetime of the platelet approximately 7-10 days . In contrast, aspirin's effect on COX-2 is reversible, and the enzyme can regain its activity once the drug is eliminated from the body.In summary, aspirin interacts with COX enzymes at the molecular level by acetylating a serine residue in the enzyme's active site, leading to a conformational change that blocks the access of arachidonic acid and ultimately inhibits the production of prostaglandins. This inhibition results in reduced pain, inflammation, and fever.