TABLE 1.
Clinical trials on gut–brain axis in PD.
| Study | Drugs | Phase | Status | NCT number |
| Investigate the digestive microbiota and bacterial translocation during IBD and PD | – | Not applicable | Recruiting | NCT04159727 |
| Treatment is able to restore the gut microbiota | Rifaximin | Phase 2 | Recruiting | NCT03958708 |
| Resistant maltodextrin for gut microbiome in Parkinson’s disease | Maltodextrin | Phase 2 | Recruiting | NCT03667404 |
| Brain–gut–microbiota axis and initiation of α-syn misfolding | – | Not applicable | Not yet recruiting | NCT03710668 |
| Gut-derived neuropeptides in cerebrospinal fluid of patients with Parkinson’s disease and healthy controls | Certain gut-derived peptides (ghrelin, GLP-1) | – | Completed | NCT01792193 |
| Effects of resistant starch on bowel habits, fecal short chain fatty acids and gut microbiota in Parkinson disease (RESISTA-PD) | Resistant starch | – | Completed | NCT02784145 |
| Study of the genome, gut metagenome and diet of patients with incident Parkinson’s disease (16S rRNA gene sequencing) | – | Recruiting | NCT04119596 | |
| Increased gut permeability to lipopolysaccharides (LPS) in Parkinson’s disease | – | – | Completed | NCT01155492 |
| Possible role of bacteria of the nose and gut in the pathogenesis of PD | – | – | Completed | NCT01536769 |
| Role of gut flora in Parkinson’s disease | – | – | Recruiting | NCT04148326 |
| Gut microbiota across early stages of synucleinopathy | – | – | Recruiting | NCT03645226 |
| Parkinson’s disease and digestive health (neuroenteric dysfunction) | – | Recruiting | NCT04032262 | |
| Probiotics-prebiotic fiber therapy in Parkinson’s disease patients with constipation | Probiotics with prebiotic | Phase 3 | Completed | NCT04451096 |
| Study of the fecal microbiome in patients with Parkinson’s disease | PRIM-DJ2727 | Phase 1 | Recruiting | NCT03671785 |
| Dietary intervention and gastrointestinal function in patients with Parkinson’s disease (MED) | Mediterranean diet | Not applicable | Active, not recruiting | NCT03851861 |
| Fecal microbiota transplantation for Parkinson’s disease | – | – | Recruiting | NCT03808389 |
| Study of the enteric nervous system using colonic biopsies in Parkinson patients with LRRK2 mutation (EnteroLarc) | – | – | Terminated (lack of patients) | NCT01618383 |