The mechanism by which dexamethasone reduces PONV is:

• A 5-HT3 receptor antagonism at the chemoreceptor trigger zone
• B D2 receptor antagonism in the area postrema
• C Not fully established; possible mechanisms include anti-inflammatory reduction of serotonin synthesis, prostaglandin inhibition, and central opioid-sparing effect ✓
• D NK1 receptor antagonism inhibiting substance P-mediated nausea

Explanation

Dexamethasone's antiemetic mechanism remains incompletely understood but is thought to involve inhibition of prostaglandin synthesis (reducing inflammatory mediators that activate the vomiting centre), reduction of central serotonin release, and opioid-sparing effects that indirectly reduce opioid-induced nausea. Its anti-inflammatory action may reduce gut motility-related nausea. Dexamethasone 4–8 mg IV at induction is one of the most cost-effective and evidence-based PONV prophylactics and acts synergistically with 5-HT3 antagonists. It is distinct from ondansetron (5-HT3 antagonist), metoclopramide (D2 antagonist), and aprepitant (NK1 antagonist).

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.