Which of the following is associated with lowest risk of causing extra pyramidal side effects?
**Core Concept**
The question is testing the knowledge of antipsychotic medications and their association with extrapyramidal side effects (EPS), which are movement disorders caused by blocking dopamine receptors in the brain, particularly in the nigrostriatal pathway.
**Why the Correct Answer is Right**
Haloperidol is a high-potency first-generation (typical) antipsychotic that primarily blocks D2 receptors. While it has a high affinity for D2 receptors, it is also known to have a relatively lower risk of causing EPS compared to other first-generation antipsychotics like chlorpromazine or trifluoperazine. This is because haloperidol has a more selective action on D2 receptors, which may reduce the incidence of EPS. However, it is essential to note that haloperidol can still cause EPS, especially at higher doses or in susceptible individuals.
**Why Each Wrong Option is Incorrect**
**Option A:** Chlorpromazine is a low-potency first-generation antipsychotic that blocks both D1 and D2 receptors. Its lower potency and broader receptor blockade profile make it more likely to cause EPS.
**Option B:** Trifluoperazine is a high-potency first-generation antipsychotic similar to haloperidol but has a higher risk of causing EPS due to its increased affinity for D2 receptors.
**Option C:** Olanzapine is a second-generation (atypical) antipsychotic that has a lower risk of causing EPS compared to first-generation antipsychotics. However, it is not the correct answer in this context, as the question specifically asks for the lowest risk among the options provided.
**Clinical Pearl / High-Yield Fact**
When choosing an antipsychotic medication, clinicians should consider the individual patient's risk factors for EPS, such as age, comorbid medical conditions, and previous exposure to antipsychotics. A lower-potency antipsychotic or an atypical antipsychotic may be a better choice for patients at higher risk of EPS.
**Correct Answer:** C.