Question:easy
What is the drug of choice for prophylaxis of motion sickness?
What is the drug of choice for prophylaxis of motion sickness?
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The anticholinergic-antihistamine antiemetic taken before the trip is best.
Updated On: Jun 23, 2026
- Promethazine
- Prochlorperazine
- Metoclopramide
- Itopride
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The Correct Option is A
Solution and Explanation
Pathway-matching trick: Match the antiemetic class to the cause. Motion sickness arises from the vestibular apparatus, signalled by acetylcholine and histamine, so the best drug must be anticholinergic and antihistaminic.
Promethazine fits perfectly: it is an H1 blocker with marked anticholinergic action, protecting for 4 to 6 hours when given roughly 30 to 60 minutes before travel. That makes it the prophylactic drug of choice (with hyoscine and dimenhydrinate as cousins).
The other three target dopamine: prochlorperazine and itopride are D2 blockers and metoclopramide is a D2 plus 5-HT3 blocker. Antidopaminergic and anti-5-HT3 drugs are weak for the vestibular trigger, so they are second-line at best.
Pearl: vestibular vomiting = antihistaminic/anticholinergic; chemical or GI vomiting = antidopaminergic.
Ref: K. D. Tripathi, antiemetics chapter.
Promethazine fits perfectly: it is an H1 blocker with marked anticholinergic action, protecting for 4 to 6 hours when given roughly 30 to 60 minutes before travel. That makes it the prophylactic drug of choice (with hyoscine and dimenhydrinate as cousins).
The other three target dopamine: prochlorperazine and itopride are D2 blockers and metoclopramide is a D2 plus 5-HT3 blocker. Antidopaminergic and anti-5-HT3 drugs are weak for the vestibular trigger, so they are second-line at best.
Pearl: vestibular vomiting = antihistaminic/anticholinergic; chemical or GI vomiting = antidopaminergic.
Ref: K. D. Tripathi, antiemetics chapter.
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