Patient description: The patient is a 55-year-old man who was recently diagnosed with Parkinson's disease. He is complaining of slowness of movement and tremors. His disease is ranked as mild, Hoehn-Yahr Stage I. His past medical history is significant for hypertension and hypercholesterolemia. He lives with his wife. They have three children. He used to be active with gardening before his diagnosis. He complains of shaking and slow movement. He had difficulty entering through a door, as he was frozen and needed guidance to step in. His handwriting is getting smaller. He is offered Levodopa and Trihexyphenidyl. He is an alert and cooperative man who does not have any signs of dementia. He does not smoke or use any illicit drugs.

Clinical trial eligibility criteria: eligible ages (years): 30.0-80.0,  Levodopa-induced Dyskinesia Male and female patients aged 30-80 years old (both ages included) Use of adequate and effective birth control measures (not including the rhythm method) during the study period and up to 3 months after the end of study in men and women of child-bearing potential or within two years of menopause (these women will perform a urine pregnancy test at the screening visit) Idiopathic Parkinson Disease (UK PD Society Brain Bank Clinical Diagnosis Criteria) diagnosed for at least 3 years Hoehn and Yahr "ON" time (good medication response) stage II-III Treatment with levodopa at an optimized dose alone or with dopamine agonists, MAO-B inhibitors or COMT inhibitors that are stable for at least 4 weeks prior to visit 1 Use of hypnotics, sedatives, beta-blockers, anxiolytics and antidepressant only if stable for at least 4 weeks prior to visit 1 A minimal baseline Levodopa induced dyskinesia score of 2 or more on question 32 (dyskinesias present during more than 25% of the waking day); a score of 2 or more on question 33 of UPDRS (severely disabling dyskinesias) Part IV (historical information) A minimal basal level of motor fluctuations of 25% or more cumulative hours of OFF time every day during waking hours on the UPDRS Part IV (a minimal score of 1 on question 39 of UPDRS, historical information) Patients have at least 33% motor improvement in response to their levodopa challenge dose based on UPDRS motor score (Part III) at visit 1 Patients experiencing peak-dose dyskinesia with a score of at least 2 on 2 or more (≥2) areas (a score of at least 4) on the modified AIMS scale in response to their levodopa challenge dose at visit 1  Patient has Non-idiopathic Parkinson's disease (e.g drug-induced or other form of secondary or atypical Parkinsonism) Neuropsychiatric exclusions: dementia (Mini Mental State Exam < 23, history or presence of psychosis (such as visual hallucinations while taking dopamine agonists), history of or current Axis I or Axis II mental disorders according to DSM-IV; severe depression (Hamilton scale > 17) Any clinically relevant acute or chronic diseases which could interfere with patients' safety during the trial, or expose them to undue risk, or which could interfere with the study objectives History or presence of gastrointestinal, hepatic, or renal disease or other condition known to interfere with the absorption, distribution, metabolism or excretion of drugs Pregnant or breast feeding women Drug abuse or history of drug abuse (including alcohol), known drug addiction Patients with severe postural hypotension (> 20 % variability between standing and supine) The following medications are forbidden for at least one month prior to visit 1 and during the course of the study: NMDA receptor antagonists (amantadine, memantine, budipine, dextromethorphan), medication with central dopaminergic antagonist activity (neuroleptics), CNS stimulants and sodium valproate (may exacerbate dyskinesias) Hoehn and Yahr score V when OFF (wheelchair-bound) The patient is participating in another study or has been participating in a study within the last 2 months