Which term describes a compound that binds to the same site as an agonist, inhibiting its binding and effect (steric mechanism)?

Which term describes a compound that binds to the same site as an agonist, inhibiting its binding and effect (steric mechanism)?

• A. Noncompetitive antagonist
• B. Competitive antagonist
• C. Irreversible antagonist
• D. Physiological antagonist

Answer: (B)

Competitive antagonism is when a compound binds to the same receptor site as the agonist, blocking binding through steric hindrance. Because this interaction is reversible, increasing the concentration of the agonist can outcompete the blocker and restore signaling. The result is a rightward shift of the agonist dose–response curve without a change in the maximum effect, reflecting that more agonist is needed to achieve the same response. This distinguishes it from noncompetitive antagonists (which bind elsewhere or change receptor function in a way that can’t be overcome by more agonist), irreversible antagonists (which form a covalent, lasting block and reduce max response), and physiological antagonists (which oppose each other through different pathways rather than competing at the same binding site).

Competitive antagonism is when a compound binds to the same receptor site as the agonist, blocking binding through steric hindrance. Because this interaction is reversible, increasing the concentration of the agonist can outcompete the blocker and restore signaling. The result is a rightward shift of the agonist dose–response curve without a change in the maximum effect, reflecting that more agonist is needed to achieve the same response. This distinguishes it from noncompetitive antagonists (which bind elsewhere or change receptor function in a way that can’t be overcome by more agonist), irreversible antagonists (which form a covalent, lasting block and reduce max response), and physiological antagonists (which oppose each other through different pathways rather than competing at the same binding site).