Inclusion Criteria:

• 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.
• Patients must be in good general health as determined by medical history, physical examination, ECG, vital signs, serum biochemistry and haematology.
• Patients must have signed an informed consent form .

Exclusion Criteria:

• 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.
• History of epilepsy and seizures.
• Any history of significant drug allergy.
• A history of unilateral or bilateral intracranial surgical procedures for Parkinson's Disease or any cerebral neurosurgery (except if occurred before the age of 18).
• History of severe pathology likely to recur during or immediately after the study.
• An inability to satisfactorily discontinue any study-forbidden medication.