A study published on the JAMA Network focused on the long-term effect of initiating pramipexole vs levodopa in early PD. The subjects were followed for up to two years and after six years. Disability was assessed using the modified Shwab and England Activities of Daily Living Scale. Other factors that were assessed included daytime sleepiness; disease severity; dopaminergic events; edema; depression; cognitive impairment and quality of life. Self-reported results were similar. Dopaminergic motor complications were more common in the initial levodopa group (68.4%) although disabling dyskinesias were uncommon in both groups. The mean (SD) Epworth Sleepiness Scale score was significantly higher in the initial pramipexole group. Mean (SD) changes from baseline in the total Unified Parkinson’s Disease Rating Scale score did not significantly differ. The study concluded that persistent differences favoring initial pramipexole were seen in the rates of dopaminergic motor complications, with less severe somnolence favoring initial levodopa.

Source: Long-term Effect of Initiating Pramipexole vs Levodopa in Early Parkinson Disease | Movement Disorders | JAMA Neurology | JAMA Network

A 2003 study published on Springer.com looked at pramipexole in comparison with I-dopa. The study subjects were twenty right-handed patients with early or mild PD. They were evaluated using neuropsychological and clinical assessments during three treatment modalities. 1. When in the off treatment condition; 2. When on pramipexole and 3. When on i-dopa. In comparison to the off treatment condition, the DA-agonist pramipexole produced a significant impairment of short term verbal memory, attentional-executive functions, and verbal fluency, while l-dopa did not. Pramipexole opposite to l-dopa, failed to improve FAS and Stroop tests. Pramipexole may worsen cognitive functions although not exceeding normative values.

Source: Pramipexole in comparison to l-dopa: a neuropsychological study | SpringerLink