Noradrenergic system is involved in impulsivity in the general population and is altered in Parkinson's disease (PD) in the early stages of the disease. Thus, targeting this system could be of interest in impulse control disorder (ICD). Acting on the noradrenergic system is possible using clonidine, an α2 adrenergic agonist largely used in hypertension treatment and that induces a decrease of NADR release. Thus, our aim is to conduct a proof of concept study evaluating the efficacy and safety of clonidine on ICD in PD. This study is a multicenter, randomized, double-blind, placebo-controlled in parallel group clinical trial.

Inclusion Criteria:

• Patients with PD according to MDS (movement disorders society) criteria for at least one year
• Patients with ICD with a QUIP-RS score ≥10 and/or at least one of the sub-scores in the following range: Pathological gambling between >6 and 12; Pathological gambling between >8 and 12; Hypersexuality between > 8 and 12; Eating between > 7 and 12. The use of "lower" margins will guarantee that patients will present behavioral disturbances severe enough to justify clonidine treatment. On the other hand, the use of "upper" margins will guarantee that the patients included in the trial will not suffer from ICD too severe to ethically participate to a placebo controlled study.
• Weight between 40 and 95kg
• Stable antiparkinsonian medication since at least 2 months before randomization and medication supposed to remain stable during the study
• ICD onset after Parkinson's disease onset and after initiation of dopaminergic drugs
• No signs of dementia (Montreal Cognitive Assessment, MOCA >20);
• No lactose intolerance which may compromise the tolerance of the placebo;
• Patients with health insurance
• Patients without judicial protection measure except directly linked to ICD
• For women of childbearing potential, an effective contraception method for at least 2 months before randomization (as implants or oral oestro-progestative contraceptives), condom use for men during the study. βHCG dosage in urine should be negative at randomization for women.

Exclusion Criteria:

Patients with major depression (BDI >19);

• Patients with another parkinsonian syndrome (Parkinson "plus" or vascular Parkinsonism)
• Orthostatic hypotension
• Patients with swallowing disorders that may prevent oral medication,
• Contraindication to clonidine: Hypersensibility; Severe bradyarythmia due to a cardiac disease
• Patients receiving a treatment potentially interacting with clonidine
• Patients with Raynaud's disease or obliterating thromboangiitis
• Patients With Heart failure or severe coronary artery disease
• Patients with a drug treatment having a potential interaction with clonidine (see list, appendix 2);
• Presence of renal failure (Cockcroft-Gault at inclusion visit<30 ml/min/1,73m2);
• Patients with a present or past history of addiction (apart ICD) or with a substance abuse (except Tabaco)
• Pregnant or lactating women
• Already participating in another biomedical research project