Question:medium
A patient with vomiting was treated with an anti-emetic drug. The patient was relieved of vomiting but developed abnormal involuntary movements. What drug should be given to manage these abnormal movements?
A patient with vomiting was treated with an anti-emetic drug. The patient was relieved of vomiting but developed abnormal involuntary movements. What drug should be given to manage these abnormal movements?
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The anti-emetic caused dopamine blockade -- think about which drug restores the dopamine-acetylcholine balance in the striatum.
Updated On: Jun 23, 2026
- Methyl dopa
- Benzhexol
- Hyoscine
- Cyproheptadine
Show Solution
The Correct Option is B
Solution and Explanation
Anti-emetics such as metoclopramide and prochlorperazine are $\text{D}_2$ receptor antagonists. Blocking dopamine in the nigrostriatal pathway creates a relative cholinergic excess, manifesting as extrapyramidal side effects (EPS) -- acute dystonia, drug-induced parkinsonism, or akathisia.
$\text{Benzhexol}$ (trihexyphenidyl, THP) is an antimuscarinic agent that blocks muscarinic $\text{M}_1$ receptors in the striatum. By reducing cholinergic activity, it restores the dopamine-acetylcholine balance and relieves EPS.
Why not the others?
- Methyl dopa: antihypertensive; can itself cause EPS
- Hyoscine: anticholinergic but not the standard choice for drug-induced EPS
- Cyproheptadine: antihistamine/antiserotonin; no role in EPS
\[\boxed{\text{Benzhexol (Trihexyphenidyl)}}\]
$\text{Benzhexol}$ (trihexyphenidyl, THP) is an antimuscarinic agent that blocks muscarinic $\text{M}_1$ receptors in the striatum. By reducing cholinergic activity, it restores the dopamine-acetylcholine balance and relieves EPS.
Why not the others?
- Methyl dopa: antihypertensive; can itself cause EPS
- Hyoscine: anticholinergic but not the standard choice for drug-induced EPS
- Cyproheptadine: antihistamine/antiserotonin; no role in EPS
\[\boxed{\text{Benzhexol (Trihexyphenidyl)}}\]
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