**Question:** A patient, Hari has been diagnosed to have schizophrenia. Which of the following acts as a limiting factor in the use of clozapine as an antipsychotic drug in this patient?

A. Neutropenia
B. Metabolic syndrome
C. Hypersensitivity to clozapine
D. QTc prolongation

**Core Concept:**
Schizophrenia is a severe mental disorder that affects cognitive, emotional, and social functioning. Clozapine is an atypical antipsychotic drug with unique properties, including high affinity for D2 and 5-HT2 receptors, which leads to better symptom control in resistant schizophrenia cases. However, clozapine is associated with several side effects that can limit its use.

**Why the Correct Answer is Right:**
Clozapine is a well-established drug for treating schizophrenia, especially in cases where other antipsychotics have failed. However, its use in Hari is limited by several factors. In this case, the correct answer is:

**Correct Answer: Hypersensitivity to clozapine (C)**

**Why Each Wrong Option is Incorrect:**

A. **Neutropenia (A):** Clozapine is an antipsychotic drug that causes a decrease in neutrophil count, leading to neutropenia, which is a serious side effect. However, this is not the primary limiting factor in Hari's case.

B. **Metabolic syndrome (B):** Clozapine is associated with an increased risk of obesity, diabetes, dyslipidemia, and hypertension. While these side effects are significant, they are not the primary limiting factor in Hari's case.

D. **QTc prolongation (D):** Clozapine can cause QTc interval prolongation, increasing the risk of torsades de pointes and sudden cardiac death. This side effect should be considered, but it is not the primary limiting factor in Hari's case.

**Clinical Pearl:**

Hypersensitivity reactions to medications can be severe and potentially life-threatening. In the context of clozapine, hypersensitivity reactions include anaphylactic reactions, angioedema, and skin reactions. It is crucial to assess the patient's medical history for any previous hypersensitivity reactions to antipsychotic drugs before prescribing clozapine.

**Explanation:**

Hypersensitivity to clozapine can manifest as anaphylactic reactions, angioedema, or skin reactions. These reactions can be severe and potentially life-threatening, making it a crucial limiting factor in considering clozapine therapy for Hari. Assessing a patient's medical history for hypersensitivity reactions to antipsychotic drugs is essential before initiating clozapine therapy.