This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Central Nervous system, Subject name: Pharmacology
The major limitation in the use of clozapine for treatment of schizophrenia is 
Select and explain. 
A. Its potential to cause agranulocytosis, B. High incidence of extrapyramidal side effects, C. Production of hyperprolactinemia, D. Its inability to benefit negative symptoms of schizophrenia
A: Its potential to cause agranulocytosis
Answer: A: Its potential to cause agranulocytosis 
Explanation: Clozapine:- It is the first atypical anti- psychotic. It has only weak D2 blocking action, produces few/no extrapyramidal symptoms; tardive dyskinesia is rare and prolactin level does not rise. Both positive and negative symptoms of schizophrenia are improved and clozapine is the most effective drug in refractory schizophrenia, i.e. patients not responding to typical neuroleptics may respond to it. Pharmacokinetics:- Clozapine is metabolized by CYP1A2, CYP2C19 & CYP3A4 into active and inactive metabolites with an average t 1/2 of 12 hours. Adverse effects:- It's major limitation is higher incidence of agranulocytosis (0.8%) and other blood dyscrasias: weekly monitoring of leucocyte count is required. Metabolic complication like weight gain, hyperlipidemia and precipitation of diabetes is another major limilation. Ref:- kd tripathi; pg num:-441