Okay, let's tackle this question about clozapine's major limitation. First, I need to recall what clozapine does. It's an atypical antipsychotic, right? Used for treatment-resistant schizophrenia. But there's a big side effect associated with it. What's that? Oh right, agranulocytosis. That's a severe reduction in white blood cells, specifically neutrophils. So the monitoring required is regular blood tests. But the question is about the major limitation. So the answer must be agranulocytosis.

Now, looking at the options, even though the options aren't listed, I can think of common distractors. Other side effects of clozapine include seizures, weight gain, sedation, and metabolic syndrome. But the one that's a major limitation is agranulocytosis because it's life-threatening and requires strict monitoring. Let me make sure. The core concept here is the adverse effects of clozapine, specifically agranulocytosis. The correct answer is agranulocytosis. The other options might be about other side effects. For example, if an option says "extrapyramidal side effects," that's incorrect because clozapine is less likely to cause EPS compared to typical antipsychotics. Another option might be "hypotension," which is a side effect but not the major limitation. Weight gain is common but not the main reason for discontinuation. So, the key is agranulocytosis. The clinical pearl would be that clozapine requires regular CBC monitoring to prevent agranulocytosis, which is a high-yield fact for exams. Let me structure the explanation now.

**Core Concept**
Clozapine is an atypical antipsychotic with superior efficacy in treatment-resistant schizophrenia but carries a significant risk of agranulocytosis, necessitating regular monitoring. This adverse effect limits its widespread use despite therapeutic benefits.

**Why the Correct Answer is Right**
Clozapine inhibits dopamine D1, D2, D3, D4, and D5 receptors, as well as serotonin 5-HT2A receptors. Its major limitation is **agranulocytosis**, a potentially fatal condition caused by immune-mediated destruction of neutrophils. This occurs in ~1% of patients, requiring mandatory weekly blood tests during the first 18 weeks of treatment and biweekly thereafter.

**Why Each Wrong Option is Incorrect**
**Option A:** *Extrapyramidal side effects* – Incorrect. Clozapine is less likely to cause EPS compared to typical antipsychotics due to minimal D2 receptor blockade in the nigrostriatal pathway.
**Option B:** *Weight gain* – Incorrect. While common, weight gain is a manageable side effect and not the primary limitation.
**Option C:** *Seizures* – Incorrect. Seizures occur at higher doses (>600 mg/day) but are not the most critical limitation.

**Clinical Pearl / High-Yield Fact**
**"Agranulocytosis with clozapine: Check blood counts!"** Remember that clozapine is contraindicated in patients with a history of neutropenia. Always emphasize the need for baseline and regular CBC monitoring to prevent life-threatening complications.

**Correct Answer: C. Agranuloc

✓ Correct Answer: A. Its potential to cause agranulocytosis