Question

Aspirin & Vioxx are both NSAIDs.

They inhibit which enzyme?

How are they different?

Answer 1

Aspirin and Vioxx are both NSAIDS (Non steroidal anti inflammatory drugs). Both of them inhibit cyclooxygenase (COX) enzyme.

This enzyme is of two types A) COX 1    B) COX 2

Vioxx is Rofecoxib is a selective COX-2 NSAID drug whereas Aspirin is non selective COX inhibitors i.e they act on both COX 1 and COX 2 enzymes.

Rofecoxib mechanism of action : It usually inhibits prostaglandin synthesis via a COX 2 inhibition and it cannot inhibit COX 1 isoenzyme. The sulfone group in the rofecoxib involves in the COX 2 inhibition. So, sulfonation is important for the inhibition of COX2

Aspirin mechanism of action : It usually inhibits both the isoforms of COX enzymes. It is usually degraded into salicylic acid and acetic acid.

The acetic acid binds irreversibly to COX 1 enzyme in the platelets, thus inhibits the formation of thromboxane A2 which is potent vasoconstrictor and platelet aggregator.

It binds to COX 2 enzyme and inhibits prostaglandin production by turning off its catalytic activity. So, acetylation is important for inhibition of both the COX enzymes