Treating Bacterial Overgrowth in Parkinson's Disease (SIBO-PD)

This study investigates the effect of treating Small Intestinal Bacterial Overgrowth (SIBO) in patients with Parkinson's Disease (PD). It will test the hypothesis that treating SIBO with the antibiotic rifaximin will improve motor complications in previously SIBO-positive PD patients.

Parkinson's Disease (PD) patients with motor fluctuations will be screened for the presence of Small Intestinal Bacterial Overgrowth (SIBO) using two hydrogen breath tests. SIBO-positive individuals will be eligible to enroll, and randomized to receive either rifaximin or placebo. This study includes two treatment regimens (including a placebo control), designed so that all patients will receive the active drug at some point during the trial. Motor outcomes will be followed for 3 or 6 months following enrollment, depending on the treatment arm to which the subject has been assigned. The primary endpoint is to assess the effect of rifaximin treatment to decrease "off" time in SIBO-positive PD patients. This pilot study will support the design of a larger, randomized controlled trial investigating the effect of SIBO eradication on reducing motor complications in PD patients with motor fluctuations. The current proposal is designed to demonstrate our ability to detect and treat SIBO in PD patients with motor fluctuations, to inform selection of the best SIBO detection method, to determine the optimal timeline for assessing motor endpoints, and to estimate the duration of benefits after treatment.

Rifaximin is an antibiotic used to treat SIBO. It is a 7-day course of treatment followed by three or six months of follow-up. This is a placebo-controlled study designed so that all participants will receive the active drug at least once during the study.

Inclusion Criteria: Diagnosis of idiopathic PD Daily "off" time ≥ 4 hours No changes in levodopa or any other dopaminergic medications expected during the course of the study Will be screened for cognitive ability (Montreal Cognitive Assessment score of ≥ 24) prior to enrollment Will be screened for presence of SIBO prior to enrollment Exclusion Criteria: Any comorbid non-PD-associated gastrointestinal (e.g., achlorhydria) or systemic diseases that may alter absorption or confound the study results Exposure to proton pump inhibitors, immunosuppressive drugs, medications that affect GI motility (such as prokinetics, anticholinergics, and tricyclic antidepressants), antibiotics or any other drugs that affect the intestinal flora (such as laxatives) within a month prior to enrollment. Prior deep brain stimulation or ablative functional neurosurgery. Prior allergy to rifaximin Women who are pregnant, lactating, or plan to become pregnant.