Gastrointestinal Dopamine Decarboxylase and Levodopa Pharmacokinetics

The main treatment for Parkinson's disease is a medication called levodopa. Levodopa has to be absorbed from the gut and travel to the brain to work, but a naturally occurring enzyme in the lining of the stomach, called dopamine decarboxylase (AADC), can break some of it down before it ever reaches the brain. We do not yet know whether people whose stomachs have more of this enzyme absorb less of their levodopa dose, have worsened gastrointestinal (GI) symptoms associated with levodopa intake, and whether that affects how well the medication controls their movement symptoms. This research may help doctors understand why levodopa works better in some people with Parkinson's disease than others, which could help improve treatment in future.

Inclusion Criteria: * Parkinson's disease * Gastric biopsies previously obtained during clinically-indicated EGD procedure * Taking dopamine replacement therapy currently Exclusion Criteria: * No history of Parkinson's disease