AADC/TDC in Advanced Parkinson's Disease

Inclusion criteria

• Participant has Parkinson's disease of at least 5 years duration, defined as time since diagnosis made by a neurologist;
• Participant is an adult, at least 25 years of age;
• Participant can read and understand Dutch;
• Participant has completed the Ethics Committee-approved Informed Consent;
• Participant is willing, competent, and able to comply with all aspects of the protocol, including not taking their PD medication during a 12-hour period, and biospecimen collection.

Exclusion criteria

• Co-morbidities that would hamper interpretation of parkinsonian disability, such as coincident musculoskeletal abnormalities, as judged by the investigators;
• Significant doubt over the correctness of the diagnosis PD, as judged by the investigators;
• Not able to stand or walk without the assistance of another person (walking aids are not an exclusion criterion);
• Never having used levodopa;
• No current use of levodopa due to lack of effect, despite never having used at least 600mg/day during at least 1 month;
• Documented allergic reaction or severe side effect to levodopa or benserazide;
• History of narrow-angle glaucoma (unless specific permission by the treating ophthalmologist for use of levodopa/benserazide);
• History of malignant melanoma (unless specific permission by the treating dermatologist for use of levodopa/benserazide);
• History of psychiatric disease with a psychotic component (unless specific permission by the treating psychiatrist for use of levodopa/benserazide);
• Known current uncompensated cardiovascular, endocrine, renal, hepatic, hematologic, or pulmonary disease (unless specific permission by the treating physician for use of levodopa/benserazide);
• Documented severe and debilitating dyskinesias on levodopa, to such an extent that levodopa treatment was terminated;
• Current pregnancy or breastfeeding;
• Co-morbidity with primary gastrointestinal pathology associated with altered gut microbiota and/or altered absorption (such as inflammatory bowel disease, celiac disease, colorectal carcinoma);
• Antibiotic use at any time during the 12 months leading up to the clinic visit;
• Current or recent (less than 1 month before clinic visit) use of (non-parkinson) drugs known or suspected to influence AADC activity, including amphetamine, dexamethasone, dopamine receptor antagonists, monoamine oxidase (MAO) inhibitors (including MAO-B inhibitors which are infrequently used as antiparkinsonian drugs), prostaglandin E2, and vigabatrin.