Low-dose intravenous erythromycin is occasionally used to accelerate gastric emptying in patients with gastroparesis. The receptor responsible for this prokinetic action is:

• A Dopamine D2 receptor antagonism
• B 5-HT4 receptor agonism
• C Motilin receptor agonism ✓
• D Muscarinic M3 receptor agonism

Explanation

At low doses erythromycin acts as an agonist at motilin receptors on gastric smooth muscle, mimicking the hormone that initiates migrating motor complex phase III contractions and thereby triggering strong antral peristalsis and gastric emptying. This action is separate from its antibacterial ribosomal effect. 5-HT4 agonism is the mechanism of prucalopride and cisapride-like agents, D2 antagonism defines metoclopramide and domperidone, and direct muscarinic agonists cause cramping rather than coordinated emptying.

Reference: Katzung's Basic and Clinical Pharmacology, 16th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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