Hyoscine (scopolamine) is used for motion sickness prophylaxis applied as a transdermal patch. The antiemetic effect is mediated by:

• A Blocking dopamine D2 receptors in the chemoreceptor trigger zone
• B Histamine H1 receptor antagonism in the inner ear
• C Serotonin 5-HT3 receptor blockade in vagal afferents
• D Muscarinic M1 receptor blockade in the vestibular nuclei and vomiting center ✓

Explanation

Hyoscine (scopolamine) prevents motion sickness through muscarinic M1 receptor blockade in the vestibular nuclei and vomiting center (nucleus tractus solitarius), reducing the cholinergic input from the inner ear labyrinth that drives motion-induced nausea. The transdermal patch delivers drug at a steady rate behind the ear, near the mastoid. Antihistamines work via H1 blockade; ondansetron via 5-HT3 blockade; and prochlorperazine via D2 blockade.

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

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Written and medically reviewed by the StethoPrep medical team.