Which statement correctly describes the mechanism of a chemical antagonist?

Which statement correctly describes the mechanism of a chemical antagonist?

• A. It binds to the receptor to block agonist
• B. It directly binds to another drug to inactivate it
• C. It produces a physiological opposite effect
• D. It binds irreversibly to the receptor

Answer: (B)

Chemical antagonism is when one substance inactivates another drug through a direct chemical interaction, not by acting at a receptor. That’s why the best statement is that it directly binds to another drug to inactivate it—think of protamine binding and neutralizing heparin. The other scenarios describe receptor-based effects or functional opposition: blocking a receptor to stop an agonist is receptor antagonism, irreversible receptor binding is a form of noncompetitive receptor antagonism, and producing the opposite effect physiologically is functional (physiologic) antagonism, not chemical inactivation.

Chemical antagonism is when one substance inactivates another drug through a direct chemical interaction, not by acting at a receptor. That’s why the best statement is that it directly binds to another drug to inactivate it—think of protamine binding and neutralizing heparin. The other scenarios describe receptor-based effects or functional opposition: blocking a receptor to stop an agonist is receptor antagonism, irreversible receptor binding is a form of noncompetitive receptor antagonism, and producing the opposite effect physiologically is functional (physiologic) antagonism, not chemical inactivation.