Treating H. Pylori in Parkinson's Patients With Motor Fluctuations

Inclusion criteria: * Adults diagnosed with idiopathic Parkinson's disease, Hoehn \& Yahr stage 2-4 in the "off" state, with no other concomitant neurologic diseases. * Stable (≥30 days) Parkinson's disease therapy, with demonstrable medication efficacy, but with wearing off phenomenon present between levodopa doses (average off time ≥3 hours off time/day). * Levodopa therapy required; Any formulation (e.g. Sinemet, Sinemet CR, Stalevo) is acceptable. Parkinson's disease treatment may also include any of the following medications or classes: non-ergot dopamine agonists, COMT inhibitors, MAO-B inhibitors, amantadine, anticholinergics. * Positive for H. pylori IgG Ab by serum ELISA (before inclusion in randomized treatment arms). Exclusion criteria: * Current abdominal pain, unexplained nausea/vomiting, or gastrointestinal bleeding. * History of gastric cancer, peptic ulcer, duodenal ulcer, or other gastric or duodenal lesions. * History of previous gastric surgery. * History of previous brain surgery for Parkinson's disease. * Family history of gastric cancer. * Prior treatment for H. pylori+ status. * Recent use (previous 4 weeks) of proton-pump inhibitor, amoxicillin, or clarithromycin. * Allergy or sensitivity to penicillin, amoxicillin, clarithromycin, or omeprazole. * Use of drugs affecting gastric motility (e.g. domperidone, metoclopramide). * Inability to tolerate or participate in testing in the morning in an "off" state. * Inability to communicate effectively with study personnel in English. * Pregnancy.