The mechanism of action of dexamethasone in PONV prophylaxis is BEST explained by:

• A D2 receptor antagonism in the chemoreceptor trigger zone
• B 5-HT3 receptor blockade in the nucleus tractus solitarius
• C Inhibition of prostaglandin synthesis reducing serotonin release in the gut and CNS ✓
• D NK1 receptor antagonism blocking substance P-mediated vomiting

Explanation

The antiemetic mechanism of dexamethasone is not fully elucidated but is primarily attributed to its anti-inflammatory effect: suppression of prostaglandin and serotonin synthesis/release in the gut wall and CNS, and possibly modulation of opioid-induced nausea via endorphin pathways. It acts centrally and peripherally. D2 antagonism is the mechanism of metoclopramide and droperidol; 5-HT3 blockade is the mechanism of ondansetron; NK1 blockade is the mechanism of aprepitant. Dexamethasone is most effective when given at induction (8 mg IV) and has an additive effect with 5-HT3 antagonists.

Reference: Morgan & Mikhail's Clinical Anesthesiology, 6th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.