Final Answer:
16A-76 Antiemetic actions of dexamethasone:
The correct answer is C. Partial antagonism of D2 receptors.
Step-by-step explanation:
Dexamethasone, a potent synthetic glucocorticoid, exerts its antiemetic actions through various mechanisms, with partial antagonism of D2 receptors playing a crucial role. The chemoreceptor trigger zone (CTZ) in the brainstem is a key area involved in the initiation of vomiting. Dexamethasone inhibits the release of neurotransmitters in the CTZ, particularly dopamine. Dopamine is known to stimulate the D2 receptors in the CTZ, leading to nausea and vomiting. By partially antagonizing these D2 receptors, dexamethasone effectively dampens the emetic response.
The antiemetic effect of dexamethasone is not solely attributed to its actions on D2 receptors. It also possesses anti-inflammatory properties that may contribute to its efficacy in preventing nausea and vomiting. Additionally, dexamethasone may reduce edema in cells of the CTZ, further diminishing the sensitivity to emetic stimuli. While the exact mechanism is not fully elucidated, the partial antagonism of D2 receptors remains a well-established and significant aspect of dexamethasone's antiemetic actions.
In conclusion, the antiemetic actions of dexamethasone involve multiple mechanisms, with the partial antagonism of D2 receptors being a prominent factor. This pharmacological effect, coupled with its anti-inflammatory properties and potential reduction of edema in the CTZ, collectively contribute to the drug's efficacy in preventing nausea and vomiting.