What does it mean for a receptor-drug interaction to be irreversible?

What does it mean for a receptor-drug interaction to be irreversible?

• A. The ligand covalently bonds to the receptor, blocking it
• B. The drug only binds temporarily
• C. The receptor rapidly dissociates
• D. The drug cannot bind to receptor

Answer: (A)

Irreversible receptor–drug interactions occur when the drug forms a covalent bond with the receptor, creating a stable, permanent inactivation of that receptor until new receptors are synthesized by the cell. Because the bond is covalent, the receptor remains occupied and unable to signal long after the drug has left the circulation, leading to a prolonged effect that tracks receptor turnover rather than drug levels. This is in contrast to reversible interactions, where noncovalent contacts allow the drug to dissociate and signaling to recover as the drug concentration falls. An example is aspirin, which irreversibly acetylates a serine in COX, permanently blocking that receptor’s activity until more enzyme is produced. If a drug only binds temporarily or dissociates rapidly, it’s not irreversible, and if it cannot bind at all, it cannot produce this effect.

Irreversible receptor–drug interactions occur when the drug forms a covalent bond with the receptor, creating a stable, permanent inactivation of that receptor until new receptors are synthesized by the cell. Because the bond is covalent, the receptor remains occupied and unable to signal long after the drug has left the circulation, leading to a prolonged effect that tracks receptor turnover rather than drug levels. This is in contrast to reversible interactions, where noncovalent contacts allow the drug to dissociate and signaling to recover as the drug concentration falls. An example is aspirin, which irreversibly acetylates a serine in COX, permanently blocking that receptor’s activity until more enzyme is produced. If a drug only binds temporarily or dissociates rapidly, it’s not irreversible, and if it cannot bind at all, it cannot produce this effect.