This project aims to develop a minimally invasive sensor device to monitor levodopa levels in real time. We will test the accuracy, tolerability, and safety of this device in people with Parkinson disease.

People with Parkinson disease (PD) lack the chemical dopamine, which is important for movement. Levodopa replaces dopamine and restores normal motor function in PD. Early in the disease stages, people with PD benefit significantly from levodopa. However, as PD progresses, the brain loses more dopamine-producing cells, which causes motor complications and unpredictable responses to levodopa. To maintain control of symptoms over time, levodopa doses must be increased and given at increasingly shorter intervals. The optimal levodopa regimen is different for each person and may vary from day-to-day, depending on a variety of internal and external factors including meal consumption, activity level, and other lifestyle variances. Currently, clinicians assess levodopa's benefit by the patient's testimony and by clinical exam. However, these methods may not adequately represent the severity or range of complications experienced by the PD patient. Thus, it can be difficult to determine the optimal levodopa treatment regimen, which can cause suboptimal disease management and side effects.

This project aims to develop a continuous, minimally invasive sensor (the "Levodopameter") designed to measure levodopa levels in real time from body fluids (capillary blood, sweat, and interstitial fluid), with the future goals of identifying an individualized treatment regimen for people with PD to improve disease management.

We will compare levodopa levels measured by the Levodopameter to the impractical and expensive "gold standard" high-performance liquid chromatography (HPLC) analysis of plasma levodopa levels. We will first test the device after administering oral carbidopa/levodopa in 10 participants with PD. After that portion of the study is completed and safety confirmed, we will test the device in 10 participants with PD after administering carbidopa and intravenous levodopa. We will also evaluate the device's safety and tolerability.

The long-term goal of this device is to allow PD patients to take proactive measures to assess and maintain an optimal, personalized levodopa regimen, similar to diabetes care in which diabetic patients periodically self-monitor their glucose and adjust their insulin regimen accordingly.

Inclusion Criteria:

1. Participants must meet the Movement Disorders Society (MDS) diagnostic criteria for clinically established Parkinson disease.
2. Able to provide signed informed consent (in English or Spanish)
3. Mild, moderate, or severe Parkinson disease, able to ambulate (Hoehn and Yahr stages I-IV)
4. Taking instant release oral carbidopa/levodopa therapy
5. Either not taking, or on stable doses of any of the following antiparkinsonian medications: dopamine agonists, monoamine oxidase B (MAO-B) inhibitors or catecholamine O-methyl transferase (COMT) inhibitors

Exclusion Criteria:

1. Other neurological conditions including but not limited to stroke, dementia (including Parkinson disease dementia), or traumatic brain injury
2. Co-existent major psychiatric disease
3. Uncontrolled, active medical conditions (e.g., heart, kidney, or liver failure, diabetes, etc.)
4. Status post deep brain stimulation (DBS) device placement
5. Any other condition, that in the opinion of the investigators, would place the participant at risk.