Maximum extrapyramidal side-effect is seen with:
**Core Concept**
Haloperidol is a typical antipsychotic medication that belongs to the butyrophenone class. Its high potency and affinity for dopamine D2 receptors contribute to its efficacy in treating schizophrenia but also increase the risk of extrapyramidal side effects (EPS).
**Why the Correct Answer is Right**
Haloperidol's high potency and affinity for dopamine D2 receptors lead to a significant blockade of these receptors in the nigrostriatal pathway, a critical region for motor control. This blockade disrupts normal dopamine signaling, resulting in EPS, which can manifest as dystonia, akathisia, parkinsonism, or tardive dyskinesia. The nigrostriatal pathway's sensitivity to D2 receptor blockade makes haloperidol particularly prone to causing EPS.
**Why Each Wrong Option is Incorrect**
**Option A:** Risperidone, while it can cause EPS, has a lower potency and affinity for dopamine D2 receptors compared to haloperidol.
**Option B:** Olanzapine has a lower risk of EPS due to its lower affinity for dopamine D2 receptors and its partial agonist activity at serotonin 5-HT2A receptors.
**Option C:** Quetiapine has a lower risk of EPS due to its lower affinity for dopamine D2 receptors and its partial agonist activity at serotonin 5-HT2A receptors.
**Clinical Pearl / High-Yield Fact**
The risk of EPS can be mitigated by using lower doses of high-potency antipsychotics or switching to lower-potency medications with a lower risk of EPS, such as risperidone or quetiapine. Regular monitoring of patients for signs of EPS and the use of anticholinergic medications can also help manage these side effects.
**Correct Answer: C. Quetiapine has a lower risk of EPS due to its lower affinity for dopamine D2 receptors and its partial agonist activity at serotonin 5-HT2A receptors.**