Treating Bacterial Overgrowth in Parkinson's Disease

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.

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.