Which of the following drug is least associated with extra-pyramidal side effects?
**Core Concept**
Extra-pyramidal side effects (EPS) are a group of movement disorders associated with the blockade of dopamine receptors in the brain, particularly in the nigrostriatal pathway. This is often seen with antipsychotic medications, which can cause symptoms such as dystonia, akathisia, and parkinsonism.
**Why the Correct Answer is Right**
The correct answer is a drug that has a lower affinity for dopamine D2 receptors, which are primarily responsible for EPS. This drug is also less likely to cause significant blockade of these receptors, resulting in fewer EPS.
**Why Each Wrong Option is Incorrect**
**Option A:** Haloperidol is a typical antipsychotic with a high affinity for dopamine D2 receptors, making it more likely to cause EPS.
**Option B:** Risperidone is an atypical antipsychotic with a moderate affinity for dopamine D2 receptors, but it also has a higher risk of EPS due to its partial agonist activity at these receptors.
**Option C:** Olanzapine is another atypical antipsychotic, but it has a lower affinity for dopamine D2 receptors and a lower risk of EPS compared to typical antipsychotics.
**Clinical Pearl / High-Yield Fact**
Atypical antipsychotics like olanzapine are generally considered to have a lower risk of EPS due to their pharmacological profile, which includes lower affinity for dopamine D2 receptors and higher affinity for serotonin 5-HT2A receptors.
**Correct Answer:** C. Olanzapine.