Influence of the Nonergot Dopamine Agonist Piribedil on Vigilance in Patients With Parkinson Disease and Excessive Daytime Sleepiness (PiViCog-PD): An 11-Week Randomized Comparison Trial Against Pramipexole and Ropinirole

Objectives: The aim of this study was to investigate the effects of piribedil on vigilance and cognitive performance in patients with Parkinson disease experiencing excessive daytime sleepiness on pramipexole or ropinirole. Methods: In this 11-week randomized, active-controlled, rater-blinded phase III study, eligible patients were randomly assigned to either receive piribedil or to continue on pramipexole or ropinirole. The primary outcome was the median reaction times during the second 15 minutes of the subtest vigilance of the Test battery for Attention Performances (TAP). Secondary outcomes included the Epworth Sleepiness Scale, Unified Parkinson's Disease Rating Scale, neuropsychological testing, and items of the Clinical Global Impression. Results: Forty-four patients received piribedil; 36 continued on either pramipexole or ropinirole. There was no difference in the primary end point reaction time of the TAP subtest vigilance between piribedil and the comparator (996 vs 954 milliseconds, P = 0.68). Piribedil reduced daytime sleepiness with lower Epworth Sleepiness Scale scores at the end of treatment compared with the comparator (-4 vs -2 points; P = 0.01). The median Unified Parkinson's Disease Rating Scale III score at the end of treatment was comparable between the 2 groups. Neuropsychological tests revealed no significant between-treatment differences. A higher therapeutic effect and global improvement were shown by the Clinical Global Impression of piribedil-treated patients. Conclusions: This study shows that switching from pramipexole or ropinirole to piribedil has no effect on the reaction time of the TAP subtest vigilance but upholds the same therapeutic motor effect and reduces daytime sleepiness to a clinically relevant degree in patients with excessive daytime sleepiness.