Overnight Switch Trial From Pramipexole IR to Pramipexole ER in Patients With Early Parkinson Disease

The objectives of this trial conducted in early Parkinson's disease (PD) patients are: * To assess if patients with early Parkinson's disease (PD) can be successfully switched (overnight switching) from Pramipexole (PPX) Immediate Release (IR) to Pramipexole Extended Release (ER). A successful switch at a specific visit is defined as no worsening of the Unified Parkinsons Disease Rating Scale (UPDRS) parts II+III score by more than 15% from baseline and no drug-related adverse events leading to withdrawal; * To establish if this successful switch can be obtained with or without dose-adaptation; * To provide information about the conversion ratio (mg:mg) from Pramipexole IR to Pramipexole ER.