Objective: To evaluate the efficacy of rifaximin as an adjunct treatment for LID (levodopa induced dyskinesia) in patients with PD through a randomized, double-blind, placebo-controlled crossover trial, using the MDS-UPDRS IV and UDysRS scales to assess motor improvement.

Background: LID affects 55.7% of PD patients after 10 years of levodopa use, involving neuroadaptation and gut-brain dysfunction. Current treatments focus on dopamine modulation but have limited efficacy and notable side effects. Rifaximin, a non-absorbable antibiotic, has eubiotic, anti-inflammatory, and neuroprotective effects, making it a potential alternative. Preliminary studies suggest benefits, but no RCTs have assessed its efficacy using standardized motor scales in PD. (1,2)

Method: We conducted the first RCT with rifaximin for LID, a phase II, randomized, double-blind, placebo-controlled crossover study. Patients with PD and LID at HGMEL received rifaximin (200 mg TID for 7 days) or placebo, randomized into two balanced sequences. Motor assessments (MDS-UPDRS IV and UDysRS) were performed at baseline and days 8, 15, and 30. This preliminary analysis includes only baseline and day 8. Paired t-tests (within-group) and independent t-tests (between-sequence) were used for statistical analysis.

Results: Demographics: Sixteen patients (56.2% female, mean age 62.2 ± 9.3 years, disease duration 10.6 ± 2.8 years). All received levodopa/carbidopa (100%), with adjunct therapies: rotigotine (43.8%), rasagiline (43%), pramipexole (18%). Patients were evenly distributed (Sequence A: n=8, Sequence B: n=8). Paired t-tests (pre-post comparison): • UDysRS: No significant change (Baseline M = 35.83, SD = 14.15; Day 8 M = 33.33, SD = 12.45); t(5) = 1.48, p = .199. • MDS-UPDRS IV: No change (M = 7.67, SD = 4.46 → 7.67, SD = 3.98); t(5) = 0.00, p = 1.00. Independent t-test (baseline comparison): • UDysRS: No difference (Sequence A: M = 41.88, SD = 14.32; Sequence B: M = 36.12, SD = 8.79); t(14) = 0.97, p = 0.349.

Conclusion: At this stage, no significant efficacy of rifaximin in LID has been observed based on MDS-UPDRS IV and UDysRS scores at day 8. These preliminary findings contrast with previous uncontrolled studies, where rifaximin showed improvements in LID. Further analysis at days 15 and 30, along with a full crossover evaluation, is necessary to determine the long-term impact of rifaximin on LID in PD.

References: 1. Fasano A, Bove F, Gabrielli M, Petracca M, Zocco MA, Ragazzoni E, et al. The role of small intestinal bacterial overgrowth in Parkinson’s disease. Mov Disord. 2013
Aug;28(9):1241–9.
2. Baizabal-Carvallo JF, Alonso-Juarez M, Fekete R. Intestinal Decontamination Therapy for Dyskinesia and Motor Fluctuations in Parkinson’s Disease. Front Neurol. 2021;12:729961.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/efficacy-of-rifaximin-as-an-adjunct-treatment-for-levodopa-induced-dyskinesia-preliminary-results/