This clinical trial focuses on Parkinson’s disease, a progressive nervous system disorder that affects movement. The study aims to improve symptom management in patients whose bodies break down levodopa (a standard medication for Parkinson’s disease) too quickly. The research will test different treatment approaches using several medications: apomorphine (a medication that directly stimulates dopamine receptors in the brain), rifaximin (an antibiotic), and a placebo.

The study will compare how well these different treatments work in patients who have difficulty with their regular Parkinson’s medication. Participants will receive either Dacepton (which contains apomorphine) as an injection under the skin, Xifaxan (which contains rifaximin) as tablets taken by mouth, or placebo capsules. Some participants will also continue taking their regular Madopar medication, which contains a combination of levodopa and benserazide.

During the study, patients will take different combinations of these medications. Domperidone tablets may be given to some participants to prevent possible side effects. The treatment period will last for several weeks, during which the effectiveness of these different approaches will be evaluated to determine which method works best for managing Parkinson’s disease symptoms in patients who have this specific problem with levodopa treatment.