Parkinsonism is induced by all drugs except –
**Core Concept**
Parkinsonism is a clinical syndrome characterized by tremors, rigidity, bradykinesia, and postural instability. It is often caused by the blockade of dopamine receptors in the basal ganglia, leading to an imbalance in the dopaminergic and cholinergic pathways.
**Why the Correct Answer is Right**
The correct answer is a drug that does not induce parkinsonism by blocking dopamine receptors. Dopamine is a neurotransmitter that plays a crucial role in movement control. Drugs that block dopamine receptors, such as antipsychotics, can cause parkinsonism as a side effect. The correct answer is likely a drug that does not affect dopamine receptors or has a different mechanism of action.
**Why Each Wrong Option is Incorrect**
**Option A:** **Haloperidol** is a typical antipsychotic that blocks dopamine D2 receptors, leading to parkinsonism as a common side effect.
**Option B:** **Metoclopramide** is a dopamine antagonist that can cause parkinsonism by blocking dopamine receptors in the striatum.
**Option C:** **Reserpine** depletes catecholamines, including dopamine, leading to parkinsonism.
**Clinical Pearl / High-Yield Fact**
Be aware that drugs that block dopamine receptors, such as antipsychotics and metoclopramide, can cause parkinsonism as a side effect. This is a common exam trap, and students should be able to identify these drugs.
**Correct Answer: D.**