Betahistine, widely used in Meniere's disease, acts primarily by:

• A Calcium channel blockade in the vascular smooth muscle of the labyrinth
• B Blockade of H2 receptors in the gastric mucosa
• C Central anticholinergic suppression of the vestibular nuclei
• D Antagonism of H3 receptors with weak H1 agonist activity, improving inner ear microcirculation ✓

Explanation

Betahistine is a structural analogue of histamine that acts as a potent H3 receptor antagonist and a weak H1 agonist. H3 antagonism increases histamine release, improving cochlear and vestibular microcirculation and reducing endolymphatic pressure. It is not a vestibular sedative, so it does not acutely abort an attack like antihistamines such as meclizine. The distractors describe unrelated drug classes: H2 blockers act on gastric acid, anticholinergics suppress vomiting centrally, and calcium channel blockers are not standard labyrinthine therapy.

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

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Written and medically reviewed by the StethoPrep medical team.