The least extrapyramidal side effects are seen with which of the following phenothiazine?
**Core Concept**
The question is testing the understanding of the pharmacological properties of phenothiazine antipsychotics, particularly their propensity to cause extrapyramidal side effects (EPS). EPS are movement disorders caused by dopamine receptor blockade in the basal ganglia.
**Why the Correct Answer is Right**
Thioridazine is a low-potency phenothiazine with a higher risk of anticholinergic side effects, which counteract the dopaminergic blockade in the nigrostriatal pathway, thereby reducing the risk of EPS. Thioridazine's anticholinergic effects are due to its high affinity for muscarinic receptors, which helps to balance the blockade of dopamine receptors in the striatum. This unique profile makes Thioridazine a better choice for patients at risk of EPS.
**Why Each Wrong Option is Incorrect**
**Option A:** Clozapine is not a phenothiazine but a second-generation (atypical) antipsychotic with a different pharmacological profile, making it an incorrect choice for this question.
**Option B:** Triflupromazine is a high-potency phenothiazine with a higher risk of EPS, similar to other high-potency antipsychotics like Haloperidol.
**Option C:** Fluphenazine is another high-potency phenothiazine with a higher risk of EPS due to its strong dopamine receptor blockade in the striatum.
**Clinical Pearl / High-Yield Fact**
When choosing an antipsychotic, consider the patient's risk of EPS, as well as their comorbid medical conditions, such as cardiovascular disease or glaucoma. Low-potency antipsychotics like Thioridazine may be a better choice for patients at risk of EPS or those with anticholinergic side effects.
**✓ Correct Answer: D. Thioridazine**