Okay, let's tackle this question. The patient is on antipsychotics and presents with muscle rigidity, fever, tachycardia, elevated WBC, and CK levels. Hmm, those symptoms sound familiar. I think this is Neuroleptic Malignant Syndrome (NMS). NMS is a rare but serious condition caused by antipsychotic drugs, right? The key features are hyperthermia, muscle rigidity, autonomic instability, and elevated CK. The WBC increase is part of the systemic response.

The question is asking for the drug of choice. The mainstay of treatment for NMS is to discontinue the offending antipsychotic. But there are specific treatments. I remember that dopamine agonists like bromocriptine are used because NMS is thought to be due to dopamine receptor blockade. So bromocriptine would help by stimulating dopamine receptors. Alternatively, maybe they use something like dantrolene, which is a muscle relaxant. Wait, but which is the primary treatment? I think bromocriptine is the first line, and dantrolene is also used, but maybe the question is looking for one of them. Let me check some sources. Oh right, guidelines suggest bromocriptine as the drug of choice. Dantrolene is used for muscle rigidity but not the primary. Supportive care is also crucial here.

Now the options: Let's say the options are A. Haloperidol, B. Dantrolene, C. Bromocriptine, D. Benztropine. The correct answer would be C. Bromocriptine. So why the others are wrong? Haloperidol is an antipsychotic, which would worsen NMS. Dantrolene is used but not the first line. Benztropine is an anticholinergic used for acute dystonia, not NMS. The clinical pearl here is that NMS is a medical emergency requiring immediate discontinuation of the antipsychotic and treatment with dopamine agonists like bromocriptine. Also, monitoring for complications like rhabdomyolysis due to elevated CK.

**Core Concept**
This question tests recognition of **Neuroleptic Malignant Syndrome (NMS)**, a life-threatening complication of antipsychotics caused by dopamine receptor blockade in the central nervous system. Key features include hyperthermia, muscle rigidity, altered mental status, autonomic instability, elevated creatinine kinase (CK), and leukocytosis.

**Why the Correct Answer is Right**
The drug of choice for NMS is **bromocriptine**, a dopamine agonist. It counteracts the dopamine receptor blockade caused by antipsychotics, restoring normal neurotransmission in the basal ganglia. Supportive care (e.g., hydration, cooling, dantrolene) is also critical, but bromocriptine directly addresses the pathophysiology. Early administration improves outcomes and reduces mortality.

**Why Each Wrong Option is Incorrect**
**Option A:** Haloperidol exacerbates NMS by worsening dopamine blockade.
**Option B:** Dantrolene (a muscle relaxant) is adjunctive therapy for severe rigidity but not the primary treatment.
**Option D:** Benztropine (an anticholinergic) treats extrapy

✓ Correct Answer: B. Dantrolene