This study tests if the antibiotic, rifaximin, can help treat patients with monoclonal gammopathy. Monoclonal gammopathy is a condition where the body makes abnormal proteins. Rifaximin works by killing bacteria in the gut, which might help reduce these abnormal proteins.

Key Points:

• The study lasts for 2 weeks, with rifaximin taken three times a day.
• After treatment, participants are monitored for an additional 8 weeks.
• Participants must not have taken antibiotics in the last 3 weeks and should use contraception during the study.

To join, you must have monoclonal gammopathy as diagnosed by a doctor and be willing to sign a consent form. If you are pregnant, or taking other treatments for gammopathy, you cannot participate. If you have allergies to rifaximin, you should not join this study. The study aims to see how safe rifaximin is and if it affects gut bacteria and abnormal proteins in the body. If you meet the criteria and are interested, please talk to your doctor or the study team for more information.