Ondansetron prevents chemotherapy-induced vomiting by blocking which receptor in the gastrointestinal tract and the chemoreceptor trigger zone?

• A Dopamine D2 receptors
• B Histamine H1 receptors
• C 5-HT3 (serotonin type 3) receptors ✓
• D Muscarinic M1 receptors

Explanation

Cytotoxic drugs trigger release of serotonin (5-HT) from enterochromaffin cells of the gut mucosa, which activates vagal afferents via 5-HT3 receptors, stimulating the vomiting centre. 5-HT3 receptors are also present in the chemoreceptor trigger zone (area postrema). Ondansetron, a selective 5-HT3 antagonist, blocks both peripheral vagal and central pathways of emesis, making it particularly effective for acute chemotherapy-induced and radiotherapy-induced nausea and vomiting.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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