**Question:** A person with violent behavior and agitation was diagnosed to have Schizophrenia and was receiving haloperidol. Following this he developed rigidity and inability to move his eyes. Which of the following drugs should be added to his treatment intravenously for this condition?

A. Benztropine
B. Fluphenazine
C. Thioridazine
D. Chlorpromazine

**Core Concept:** Schizophrenia is a severe mental disorder characterized by disordered thinking, emotions, and behavior. Haloperidol is a dopamine D2 receptor antagonist, commonly used to treat psychosis in schizophrenia. However, the development of extrapyramidal side effects (EPS) can occur due to the blockade of D2 receptors in the extrapyramidal system.

**Why the Correct Answer is Right:** When EPS occur, dopamine blockade is more pronounced in the extrapyramidal system (locus coeruleus, substantia nigra, and globus pallidus) compared to the cerebral cortex, leading to the development of symptoms like rigidity, tremors, and dystonia. Benztropine is a CNS dopamine D2 and D3 receptor antagonist, specifically targeting the extrapyramidal system, and can effectively manage these side effects.

**Why Each Wrong Option is Incorrect:**

**A. Fluphenazine:** Although a dopamine D2 receptor antagonist, its mechanism of action differs from Benztropine. Fluphenazine is a potent neuroleptic drug with more affinity for D2 receptors in the cerebral cortex, which may lead to worsening of EPS.

**B. Thioridazine:** Similar to Fluphenazine, Thioridazine is a neuroleptic drug with a higher affinity for D2 receptors in the cerebral cortex. This may result in worsening of EPS due to increased dopamine blockade in the extrapyramidal system.

**C. Chlorpromazine:** Chlorpromazine is another neuroleptic drug, with a higher affinity for D2 receptors in the cerebral cortex. Like the previous options, it increases dopamine blockade in the extrapyramidal system, worsening the EPS.

**Clinical Pearl:** In patients with schizophrenia and EPS due to dopamine D2 receptor blockade, the choice of antipsychotic medication is crucial. Selecting dopamine D2 receptor antagonists with lesser affinity for cerebral cortex receptors, like Benztropine, can help manage the EPS without worsening the core symptoms of schizophrenia.