The investigators are interested in evaluating the use of oral N-acetylcysteine (NAC) as therapy for Parkinson's Disease (PD) and measuring changes in brain and blood chemistry.

The investigators are interested in evaluating the use of oral N-acetylcysteine (NAC) as therapy for Parkinson's Disease (PD) and measuring changes in brain and blood chemistry. The investigators' hypothesis is that repeated oral dosing of NAC will result in increased brain and red blood cell GSH concentrations in individuals with Parkinson's disease (PD) and healthy controls. The specific aims are to 1.) measure plasma and blood (red blood cell) glutathione (GSH) and ratio of reduced GSH to oxidized glutathione (GSSG) in individuals with PD and healthy controls at baseline and after four weeks of repeated high doses of oral NAC (6000 mg/day) and 2) measure cortical GSH levels (as ascertained through MRS) in those with PD and healthy controls at baseline and four weeks during repeated high doses of oral NAC (6000 mg/day) simultaneously with Aim 1. This study will combine information from a medical history, a physical examination, and disease rating scales with results obtained using Magnetic Resonance Spectroscopy (MRS) brain scans and pharmacokinetic studies from blood samples. This research will require 2 visits, one at baseline and one after approximately 28 days of therapy. Participants will provide their medical history during the first visit, and undergo a physical examination and rating scale each visit (duration: 1 hour). The first visit including the brain scans and blood collection will require approximately 3 hours of time. The brain scan and pharmacokinetic studies for the second visit will require approximately 8 hours of time. In total the second visit will take roughly 9 hours.

Inclusion Criteria:

1. All participants must be 18 years or older
2. All enrollees must understand and cooperate with requirements of the study in the opinion of the investigators and must be able to provide written informed consent
3. Individuals with medically stable Parkinson's disease (in the opinion of the investigator)
4. All participants must not have taken antioxidants NAC, glutathione, coenzyme Q-10, vitamin C, or vitamin E for 3 weeks prior to the study
5. Absence of dementia in all subjects

Exclusion Criteria:

1. Inability to undergo MRI scanning without sedation and other MRI counterindications, such as metal in the body (see section 7.3)
2. Medically unstable conditions as determined by the investigators
3. Pregnant or lactating or those women of child-bearing age that are not using acceptable forms of contraception
4. Diagnosis of asthma that is presently being treated with any medication, or past history of asthma/bronchospasm resulting in an emergency room visit, hospitalization or treatment
5. Unable to adhere to study protocol for whatever reason

6 weeks