What is a common result of downregulating receptors due to regular administration of a drug antagonist?

Downregulating receptors as a consequence of regular administration of a drug antagonist generally leads to decreased sensitivity to the agonist. This occurs because the presence of an antagonist can cause the body to adjust by reducing the number or sensitivity of receptors in response to the persistent blockade of agonist activity. When fewer receptors are available or when they are less responsive, the physiological effects of any subsequent agonist binding will be diminished, resulting in decreased sensitivity.

This adaptation serves as a compensatory mechanism, as the body attempts to maintain homeostasis in the absence of normal receptor stimulation. Over time, the presence of the antagonist leads to a reduced response to the agonist, reinforcing the idea that chronic exposure can alter receptor dynamics and functionality. This concept is particularly important for understanding the pharmacodynamics involved in long-term pharmacotherapy with antagonists.

The other responses are less accurate; for example, increased receptor density typically occurs in response to chronic antagonist use rather than decreased sensitivity. Enhanced agonist effects would suggest heightened receptor activity, contrary to what is expected with receptor downregulation. Worsening of symptoms due to receptor loss might be a consequence of overall receptor signaling disruption, but the primary and most direct result of downregulation is decreased sensitivity, making it the most appropriate answer