Which statement is not true about an irreversible antagonist?

Which statement is not true about an irreversible antagonist?

• A. Binds to the receptor site and forms a covalent bond
• B. Typically produces effects that cannot be readily reversed
• C. Shifts the dose-response curve to the right and downward
• D. Its effect is completely reversible when sufficient time passes

Answer: (D)

An irreversible antagonist works by forming a permanent bond with the receptor, often covalently, permanently inactivating those receptor sites until new receptors are made. Because the receptor is effectively blocked long-term, the drug’s effects persist and aren’t easily washed out or reversed simply by waiting. This is why an irreversible antagonist typically reduces the maximal effect achievable (Emax) and causes a rightward and downward shift in the agonist dose–response curve. Recovery depends on the synthesis of new receptors, not on time alone. Therefore, the idea that its effect is completely reversible with enough time is not true, making that statement the incorrect one. The other statements align with the known behavior of irreversible antagonists.

An irreversible antagonist works by forming a permanent bond with the receptor, often covalently, permanently inactivating those receptor sites until new receptors are made. Because the receptor is effectively blocked long-term, the drug’s effects persist and aren’t easily washed out or reversed simply by waiting. This is why an irreversible antagonist typically reduces the maximal effect achievable (Emax) and causes a rightward and downward shift in the agonist dose–response curve. Recovery depends on the synthesis of new receptors, not on time alone. Therefore, the idea that its effect is completely reversible with enough time is not true, making that statement the incorrect one. The other statements align with the known behavior of irreversible antagonists.