Buspirone Treatment of Iatrogenic Dyskinesias in Advanced Parkinson' Disease

Inclusion Criteria * The subject is an out-patient between 35 year and 80 years of age * Diagnosis of idiopathic Parkinson's disease according to the UK Parkinson's Disease Society Brain Bank Clinical Diagnosis Criteria * Dyskinesias are present more than 25% of the waking day according to item 4-1 of MDS-UPDRS * Dyskinesias are at least moderately disabling item 4-2 of MDS-UPDRS replaced by Dyskinesias are at least slightly disabling item 4-2 of MDS-UPDRS (amendment n°2) * The subject is able to identify dyskinesia, ON and OFF, and apply to his/her own state * Stable dose of anti-Parkinsonian drugs for at least 4 weeks up to the screening * The subject is considered as being optimally treated at the time of inclusion * Written and signed informed consent to participate in the study * Maximal Hoehn and Yahr staging : III in "ON" phases, IV in "OFF" * Active affiliation to social security * Menopausal or under contraception for woman Exclusion Criteria * Female subjects : pregnant or lactating * Atypical parkinsonian syndrome * Weight less than 40 Kgs * Mini-Mental State Examination (MMSE) less than 24 * The subject is participating in another clinical study within the past 12 weeks * Planned participation in another therapeutic clinical study * Previous treatment with buspirone, less than 6 months before Week 0 * Known allergy to buspirone * Known lactose intolerance * Clinically significant illness that might interfere with the study * Dementia or other psychiatric illness * Drug or alcohol abuse replaced by Substance use disorder (alcohol i.e. \> 3 drinks per day for men and \> 2 drinks per day for women,drug, medicinal product) (amendment n°1) * Legal incapacity or limited legal capacity * Deep brain stimulation performed less than 12 months before protocol initiation, or unstable parameters of stimulation 4 weeks before week 0 * Severe renal and / or hepatic impairment * History of seizures or epilepsy