Conjecture 17. Dopamine agonists increase the risk of somnolence as compared to levodopa.

Etminan et al. write [1]:

"Four trials were included in the analysis of patients taking pramipexole or ropinirole compared with those taking placebo. The pooled relative risk of somnolence in this analysis was 4.98 [95% confidence interval (CI) 1.79 to 13.89]. Seven trials were included in the analysis of patients taking levodopa and pramipexole or ropinirole compared with those taking levodopa alone. The pooled relative risk was 2.06 (95% CI 1.47 to 2.88)."

Salawu and Olokoba write [2]:

"The importance of addressing EDS [excessive daytime sleepiness] in PD was highlighted by a report of eight patients who suddenly fell asleep while driving a motor vehicle. ... These episodes were termed "sleep attacks" by the author because they seemed to have occurred without warning, and were attributed to dopamine agonists because they disappeared when the drugs were withdrawn."

References

[1] Abstract only.
Drug Saf. 2001;24(11):863-8.
"Increased risk of somnolence with the new dopamine agonists in patients with Parkinson's disease: a meta-analysis of randomised controlled trials."
Etminan M1, Samii A, Takkouche B, Rochon PA.
http://www.ncbi.nlm.nih.gov/pubmed/11665873

[2] "Excessive Daytime Sleepiness and Unintended Sleep Episodes Associated with Parkinson’s Disease"
Fatai Salawu1,* and Abdulfatai Olokoba
Oman Med J. 2015 Jan; 30(1): 3–10
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4371466/

John