This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: ANS, Subject name: Pharmacology
A patient was treated with haloperidol, later he develops symptoms of Parkinsonism. What is the best treatment: 
Select and explain. 
A. Cholinesterase inhibitors, B. Beta receptor antagonist, C. M1 muscarinic antagonist, D. Alpha 1 adrenergic antagonist
C: M1 muscarinic antagonist
Answer: C: M1 muscarinic antagonist 
Explanation: - Extrapyramidal disturbances are the major dose-limiting side effects with high potency antipsychotics like fluphenazine, haloperidol, pimozide, etc. - The extrapyramidal effects may be categorized into: Parkinsonism Acute muscular dystonias Akathisia Malignant neuroleptic syndrome Tardive dyskinesia - Parkinsonism usually appears between 1-4 weeks of therapy and it persists untill dose is reduced. If that is not possible, one of the anticholinergic anti-parkinsonian drugs may be given concurrently. - The M1 antagonists are drug of choice for drug induced parkinsonism. (Benzhexol).