A Double-blind, Double-dummy, Randomized, Parallel Groups Study to Assess the Efficacy, Safety and Tolerability of Switching Patients With Early Parkinson's Disease (PD) From Pramipexole IR to Pramipexole ER or Pramipexole IR

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.