Small intestinal bacterial overgrowth (SIBO) is a condition caused by the presence of excessive bacteria in the small intestine. It frequently causes chronic diarrhea and malabsorption of food. Rifaximin is the most widely prescribed antibiotic for SIBO, succeeding in roughly one-half of cases in one week. Doctors frequently prescribe Xifaxan in combination with another antibiotic, neomycin. Together, they have been shown to be effective in almost 85% of cases after ten days.