Gut bacteria tweak could boost Parkinson's drug response
NCT ID NCT03575195
First seen Jun 26, 2026 · Last updated Jun 26, 2026
Summary
This study explores whether altering gut bacteria with an antibiotic (rifaximin) can improve motor symptoms and medication response in people with Parkinson's disease. Researchers will first analyze how gut bacteria relate to symptoms, then give some participants rifaximin and others a placebo. The goal is to see if reducing certain bacteria can help levodopa work better and reduce 'OFF' time. The trial is currently suspended.
What this could mean
Our plain-language read of the trial. This is informational only, not medical advice or a prediction.
- Active substance
- Rifaximin (an antibiotic)
- What this could lead to
- If it works, this could point toward a way to improve Parkinson's symptoms and make standard medications work better by adjusting gut bacteria.
- What could go wrong
- This is an early, small trial that is currently suspended. The antibiotic approach may not change symptoms meaningfully, and gut bacteria changes might not last.
This is an AI summary of the original study and may miss details. Read our disclaimer.
Study facts
What this study's own registry entry says, in plain language.
- Phase
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Phase 1/2
Runs two stages together: safety and dose first, then whether the treatment works.
- Participants
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About 86 people
The number the study aims to enrol. It can still change while the study runs.
- Started
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Jul 2019
- Expected to finish
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Aug 2026
An estimate. End dates often move.
- Lead sponsor
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Other sponsor
The registry's catch-all category, for sponsors it does not file as a company, a government agency, or a research network.
Who can take part
This study's own entry requirements. Only the study team can say for certain whether you qualify.
- Ages
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30 years and older
- Sex
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Anyone
- Healthy volunteers
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Not accepted
This study is not open to healthy volunteers. The entry requirements below say who it is open to.
Show the full entry requirements Hide the full entry requirements
Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.
Inclusion Criteria: * Parkinson's disease * Stable on levodopa therapy with fluctuations Exclusion Criteria: * Chronic gastrointestinal disease * Recent antibiotic or probiotic therapy * Pregnant * Immunocompromised
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Conditions
The condition(s) this trial relates to.
As listed by the trial registrant
The condition terms exactly as the trial's registrant entered them.
How to take part
Only the study team decides who joins. These are the ways to reach them.
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The places running it
1 site. The list below names each one and where it is.
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The official record
The full official record for this study. This one lists no contact details, but it is the first place any would appear.
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A doctor treating you
A doctor who knows your case can contact a study site on your behalf, and can tell you whether this study is worth pursuing at all.
Contacts and locations
Locations
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University of California San Francisco
San Francisco, California, 94115, United States
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