Rifaximin is a semi-synthetic, non-systemic antibiotic derived from rifamycin SV. It acts locally in the gastrointestinal tract with minimal systemic absorption (<1%). It is indicated for the management of travelers' diarrhea caused by non-invasive strains of Escherichia coli, reduction in risk of overt hepatic encephalopathy (HE) recurrence, and irritable bowel syndrome with diarrhea (IBS-D). Its unique property of minimal absorption makes it suitable for long-term use in certain conditions with a favorable safety profile.
Adult: Hepatic Encephalopathy (reduction of recurrence): 550 mg orally twice daily. Travelers' Diarrhea: 200 mg orally three times daily for 3 days (Note: 550mg strength is not typically used for this; 200mg tab is used). IBS-D: 550 mg orally three times daily for 14 days; may be repeated up to two times if symptoms recur.
Note: Tablet should be swallowed whole with a glass of water. Can be taken with or without food. For travelers' diarrhea, it should be taken at the first sign of illness.
Rifaximin binds to the beta-subunit of bacterial DNA-dependent RNA polymerase, resulting in inhibition of bacterial RNA synthesis. This bactericidal action is specific to bacteria and does not affect mammalian RNA polymerase.
Pregnancy: Category C: Animal studies have shown adverse effects. There are no adequate and well-controlled studies in pregnant women. Use only if the potential benefit justifies the potential risk to the fetus.
Driving: Patients should be cautioned about potential dizziness and fatigue, which may impair the ability to drive or operate machinery.
| Cyclosporine | Rifaximin may potentially decrease cyclosporine efficacy by altering gut flora and reducing its conversion to active metabolite. Monitor cyclosporine levels. | Moderate |
| Warfarin | Theoretical interaction due to alteration of vitamin K-producing gut flora, potentially affecting INR. Monitor INR closely when starting or stopping rifaximin. | Moderate |
| Oral Contraceptives | No significant interaction expected due to lack of systemic absorption. However, in cases of severe diarrhea/vomiting, contraceptive efficacy may be reduced. | Minor |
Same composition (Rifaximin (550mg)), different brands: