Clinical trial investigates solriamfetol for excessive daytime sleepiness in Parkinson's disease with promising results
For individuals living with Parkinson's disease, the challenges extend far beyond the characteristic motor symptoms most people associate with the condition. Among the most debilitating and often overlooked aspects is excessive daytime sleepiness (EDS) - an overwhelming, uncontrollable need to sleep during waking hours that significantly impacts quality of life 1 . This sleepiness isn't simply feeling tired; it's a pervasive symptom that can make everyday activities like driving, working, or socializing difficult or even dangerous.
Excessive daytime sleepiness affects approximately one-third of Parkinson's patients, though some estimates suggest even higher rates 2 .
Traditional approaches to managing Parkinson's symptoms often leave EDS unaddressed, creating a critical treatment gap that researchers have been working to fill. In a promising development, a recent clinical trial has investigated whether solriamfetol - a medication already approved for sleepiness in other conditions - might offer relief 3 . This research represents an important step toward improving daily life for the millions worldwide navigating the complex landscape of Parkinson's disease.
Parkinson's disease is primarily recognized as a movement disorder, characterized by tremors, stiffness, and balance problems resulting from the progressive loss of dopamine-producing neurons in the brain. However, the impact of Parkinson's extends throughout the nervous system, disrupting multiple aspects of daily functioning.
Research indicates that EDS affects approximately one-third of Parkinson's patients, though some estimates suggest even higher rates 2 .
EDS has been identified as an independent risk factor for reduced survival in Parkinson's disease 4 .
The consequences of EDS extend far beyond simple inconvenience. Daytime sleepiness increases fall risk, impairs cognitive function, reduces quality of life, and creates substantial caregiver burden. This sleepiness stems from multiple factors: the underlying disease process affecting brain regions regulating sleep-wake cycles; poor nighttime sleep quality due to symptoms; and sometimes, side effects of Parkinson's medications themselves 5 .
Solriamfetol (marketed under the brand name Sunosi™) represents a novel approach to promoting wakefulness. Understanding its mechanism requires a quick look at how the brain regulates alertness.
Selective Dopamine and Norepinephrine Reuptake Inhibitor (DNRI)
Dopamine
Norepinephrine
This targeted mechanism allows solriamfetol to promote wakefulness without some of the more dramatic peaks and crashes associated with traditional stimulants. The medication is taken once daily, reaching peak concentration in about two hours, with effects lasting throughout the day 6 .
To evaluate whether solriamfetol could help with EDS in Parkinson's specifically, researchers designed a rigorous Phase 2 proof-of-concept trial published in 2021 3 . This study represents one of the first dedicated investigations of solriamfetol for this particular application.
The trial employed a double-blind, placebo-controlled, crossover design - considered the gold standard for clinical research because it provides the most reliable evidence about a treatment's true effects.
The study included 66 adults with Parkinson's disease and clinically significant excessive daytime sleepiness (defined by Epworth Sleepiness Scale scores ≥10). Participants were recruited across 33 sites in the United States between 2017 and 2018.
The research design featured three treatment sequences with different dose progressions and placebo controls, allowing for comprehensive comparison of effects across different dosage levels.
Each treatment period lasted one week, with assessments conducted weekly to evaluate safety, tolerability, and efficacy.
The results of this careful investigation provided important insights into both the potential benefits and limitations of solriamfetol for Parkinson's-related EDS.
The trial yielded interesting, though mixed, results on solriamfetol's effectiveness:
Greater negative values indicate greater improvement in sleepiness
Positive values indicate improvement in ability to stay awake
"The 300 mg dose produced a statistically significant benefit compared to placebo in objective measures of wakefulness."
The trial provided reassuring data about solriamfetol's safety in the Parkinson's population:
| Adverse Event | Percentage of Participants |
|---|---|
| Nausea | 10.7% |
| Dizziness | 7.1% |
| Dry Mouth | 7.1% |
| Headache | 7.1% |
| Anxiety | 5.4% |
| Constipation | 5.4% |
The mixed results from this trial - significant objective improvement in wakefulness without corresponding subjective benefits - raise interesting questions for future research. The disconnect between how alert patients objectively were versus how alert they felt subjectively warrants further investigation.
"The safety profile observed was consistent with solriamfetol's known effects, with no unexpected safety concerns emerging in the Parkinson's population."
The investigation of solriamfetol for Parkinson's-related excessive daytime sleepiness exemplifies how repurposing existing medications can efficiently address troublesome symptoms that diminish quality of life. While questions remain, the objective improvement in wakefulness - particularly at the 300 mg dose - offers hope that better management of this debilitating symptom may be on the horizon.
For the millions living with Parkinson's worldwide, research like this represents more than just scientific progress - it represents the possibility of more alert, engaged, and fulfilling days despite their diagnosis. As research continues, the goal remains clear: not just adding years to life, but life to years, one wakeful day at a time.