Erythromycin accelerates gastric emptying when given to a patient with diabetic gastroparesis. The property responsible for this non-antibiotic use is:

• A Inhibition of gastric CYP3A4 metabolism of prokinetic peptides
• B Stimulation of local prostaglandin E2 release in the antrum
• C Blockade of inhibitory presynaptic muscarinic autoreceptors
• D Agonism at motilin receptors on gastrointestinal smooth muscle ✓

Explanation

Erythromycin is a direct agonist at motilin receptors, mimicking the natural peptide that coordinates migrating motor complex activity. At low doses it induces strong gastric and intestinal contractions, which is exploited off-label in diabetic gastroparesis and before endoscopy. It has no cholinergic or prostaglandin-mediated prokinetic action, and its CYP3A4 inhibition causes interactions rather than prokinesis. Azithromycin shares some motilin activity but erythromycin is the classic exam answer.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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