Rifaximin for Opioid use disorder | Substance use disorder

Inclusion criteria

• {"criterion_text":"- Diagnosis of OUD according to DSM‑5 criteria\n- patients in the early phase of withdrawal or in treatment with the intention to discontinue opioid use\n- age between 18 and 60 years\n- for female participants, not pregnant and not breastfeeding\n- ability to understand and sign informed consent\n- Patients with recent abstinence (e.g., within 1–4 weeks from last opioid use) will be preferentially included to capture the early adaptation phase, but not those in uncontrolled acute withdrawal\n- Patients receiving methadone maintenance treatment are eligible, provided they are on a stable dose and willing not to modify it for at least the first month of the study."}

Exclusion criteria

• {"criterion_text":"- Presence of known organic gastrointestinal diseases (e.g., Crohn’s disease, ulcerative colitis, untreated celiac disease, advanced-stage liver cirrhosis, GI malignancies) that may significantly alter intestinal permeability or contraindicate biopsy\n- diagnosis of active chronic infection\n- severe uncontrolled medical conditions\n- active psychiatric disorders that impair cooperation\n- current use of antibiotics or probiotics that significantly alter the microbiota (requiring at least a 4‑week washout before the study)\n- HIV/AIDS or immunocompromised status\n- known allergy or severe adverse reaction to rifaximin or to antibiotics of the rifamycin class\n- for women, confirmed or planned pregnancy during the study period.\n- Concurrent participation in other interventional clinical trials\n- inability to comply with study procedures"}

Primary endpoints

• {"endpoint_text":"- Intensity of opioid craving","definition_or_measurement_approach":""}
• {"endpoint_text":"- Indicators of social isolation/disconnection","definition_or_measurement_approach":""}
• {"endpoint_text":"- Tapering of methadone therapy","definition_or_measurement_approach":""}

Secondary endpoints

• {"endpoint_text":"- Intestinal permeability measures","definition_or_measurement_approach":""}
• {"endpoint_text":"- Fecal microbiota characteristics","definition_or_measurement_approach":""}
• {"endpoint_text":"- Adverse events and infections","definition_or_measurement_approach":""}

Italy

Earliest CTIS Part Ii Submission Date

16-04-2026

Latest Decision Or Authorization Date

29-04-2026

Processing Time Days

13

Number Of Sites

2

Number Of Participants

50

Primary sponsor

Full Name

Fondazione Santa Lucia

Organisation Type

Hospital/Clinic/Other health care facility

Country Of Registered Address

Italy