Rifaximin SSD in Dementia Trial

This study is testing whether rifaximin — an antibiotic that works mainly in the gut — can slow cognitive decline in people with Alzheimer's disease or vascular dementia. The theory is that changes in gut bacteria may contribute to brain inflammation and memory loss, and that an antibiotic targeting gut bacteria might help. **You may be eligible if...** - You are 65 years or older - You have a diagnosis of probable Alzheimer's disease or vascular dementia at a mild or moderate stage - You live in the community (not in a nursing home) and have a caregiver who can attend appointments with you - You (or your legal guardian) can give informed consent - You and your caregiver both speak and read English **You may NOT be eligible if...** - Your dementia is caused by something other than Alzheimer's or vascular disease - You have significant agitation, delusions, hallucinations, or severe depression - You have poorly controlled or severe medical conditions - You have a hearing or vision problem that prevents completing tests - You are allergic to rifaximin or related antibiotics - You have taken antibiotics in the last 6 months - You have a history of alcohol or drug abuse Talk to your doctor to see if this trial is right for you.