The primary purpose of this study is to demonstrate that early introduction of treatment with amantadine (200 mg / d) in the early years of therapeutic care, that is to say during the "honeymoon" of levodopa (early phase of disease <3 years of diagnosis <1 year of L-dopa and lack of complications of levodopa therapy) decreases the rate of subjects with abnormal involuntary dyskinetic movements after 18 months of follow-up.