This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: C.N.S, Subject name: Pharmacology
Antiviral drug amantadine is approved for: 
Select and explain. 
A. Achizophrenia, B. Depression, C. Alzheimer's disease, D. Parkinsonism
D: Parkinsonism
Answer: D: Parkinsonism 
Explanation: (Ref: Katzung, 14th ed. pg. 501)* Amantadine is an antiviral for Influenza A. It has been approved for treatment for Parkinson disease as well.* Best for early stage PD or if patient not responding to L-Dopa* Mechanism of action* Facilitate DA release from presynaptic dopaminergic neuron and also Prevents DA uptake* Side effect: Confusion, Hallucination, Ankle edema, Livido reticularis