Which statement best distinguishes desensitization from tolerance?

Which statement best distinguishes desensitization from tolerance?

• A. Desensitization involves receptor inactivation during prolonged exposure; tolerance is reduced response after repeated dosing.
• B. Desensitization and tolerance are the same phenomenon.
• C. Desensitization is irreversible; tolerance is reversible.
• D. Desensitization only occurs in the CNS.

Answer: (A)

The key idea is that desensitization and tolerance describe different ways the body becomes less responsive to a drug. Desensitization is a receptor-level change that happens during sustained exposure: the receptor becomes inactivated or uncoupled from its signaling machinery, so the response falls even if the drug is still bound. This is often rapid and reversible when the drug is removed. Tolerance, on the other hand, refers to a reduced effect after repeated dosing over time, due to broader adaptations such as changes in receptor density, altered signaling, or increased drug metabolism; the diminished response can persist even when exposure is reduced or stopped and may take longer to develop or reverse. So the statement that desensitization involves receptor inactivation during prolonged exposure and tolerance is the reduced response after repeated dosing best captures the distinction. The other options are not accurate: desensitization is not typically described as irreversible, nor is it confined to the CNS, and they are not the same phenomenon.

The key idea is that desensitization and tolerance describe different ways the body becomes less responsive to a drug. Desensitization is a receptor-level change that happens during sustained exposure: the receptor becomes inactivated or uncoupled from its signaling machinery, so the response falls even if the drug is still bound. This is often rapid and reversible when the drug is removed. Tolerance, on the other hand, refers to a reduced effect after repeated dosing over time, due to broader adaptations such as changes in receptor density, altered signaling, or increased drug metabolism; the diminished response can persist even when exposure is reduced or stopped and may take longer to develop or reverse.

So the statement that desensitization involves receptor inactivation during prolonged exposure and tolerance is the reduced response after repeated dosing best captures the distinction. The other options are not accurate: desensitization is not typically described as irreversible, nor is it confined to the CNS, and they are not the same phenomenon.