What are the only 2 medications on the NBEO matrix that bind irreversibly?

• A. Aspirin and Echothiophate
• B. Aspirin and Ibuprofen
• C. Aspirin and Indomethacin
• D. Aspirin and Naproxen sodium

Answer: (A)

Irreversible inhibition happens when a drug forms a covalent bond with its target, permanently inactivating the enzyme until new enzyme is made. Aspirin acetylates the active site of cyclooxygenase enzymes, giving permanent loss of their activity. Echothiophate is an organophosphate that phosphorylates acetylcholinesterase, also causing permanent inhibition. The other NSAIDs listed (ibuprofen, indomethacin, naproxen) bind reversibly to COX enzymes; their effects wear off as the drug dissociates and new enzyme is synthesized. So the two medications that bind irreversibly are aspirin and echothiophate.