A patient presented with history of few episodes of vomiting and was given an anti-emetic drug by the intern. Few hours later, the patient developed an abnormal posture. Which of the following is likely drug administered to him ?
First, the core concept here is probably about extrapyramidal side effects of anti-emetics. Drugs like metoclopramide or prochlorperazine can cause dystonia, which is an abnormal muscle contraction leading to postures.
The correct answer is likely one of these drugs. Let's say the options include metoclopramide, ondansetron, promethazine, and chlorpromazine. Wait, but the options aren't given here. The user didn't provide the options, so I need to make assumptions based on the scenario.
Abnormal posture after an anti-emetic suggests dystonia. Common culprits are dopamine antagonists. Metoclopramide is a dopamine antagonist and can cause acute dystonia. Ondansetron is a serotonin antagonist and less likely to cause this. Promethazine and chlorpromazine are antihistamines but chlorpromazine is a phenothiazine, which can cause dystonia too.
So if the correct answer is metoclopramide, the explanation would focus on its dopamine antagonism leading to extrapyramidal symptoms. Other options like ondansetron don't cause this. The clinical pearl is that dopamine antagonists like metoclopramide can cause acute dystonia, especially in young patients. The answer is likely metoclopramide, so the correct answer letter would be C or D depending on the options.
**Core Concept**
This question assesses knowledge of extrapyramidal side effects caused by dopamine receptor antagonists. Anti-emetics like metoclopramide or prochlorperazine block dopamine D2 receptors in the basal ganglia, leading to acute dystonia characterized by involuntary muscle contractions and abnormal postures.
**Why the Correct Answer is Right**
Metoclopramide, a dopamine antagonist, is a high-yield drug associated with acute dystonia. It inhibits dopamine signaling in the nigrostriatal pathway, disrupting motor control. This manifests as opisthotonus, trismus, or torticollis within hours of administration. The abnormal posture described is classic for this adverse effect, particularly in young patients or those with predisposing factors (e.g., renal impairment).
**Why Each Wrong Option is Incorrect**
**Option A:** Ondansetron (a 5-HT3 receptor antagonist) lacks dopamine antagonism and does not cause dystonia.
**Option B:** Promethazine (a first-generation antihistamine) may cause sedation but not acute dystonia.
**Option D:** Chlorpromazine (a phenothiazine antipsychotic) can cause dystonia, but it is not typically used as a first-line anti-emetic in this context.
**Clinical Pearl / High-Yield Fact**
Remember the "D" drugs: **D**opamine antagonists (e.g., metoclopramide, prochlorperazine) are notorious for **D**ystonia. Administering diphenhydramine or benztropine can reverse acute dystonia. Avoid these agents in young patients unless benefits outweigh risks.
**Correct Answer: C. Metoclopramide**