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 a first-line therapy for traveler's diarrhea caused by non-invasive strains of E. coli and is a cornerstone in the management of hepatic encephalopathy (HE) in India. Its gut-selective action minimizes systemic side effects and drug interactions.
Adult: Traveler's Diarrhea: 200 mg orally three times a day for 3 days. Hepatic Encephalopathy: 550 mg twice daily (Note: 200mg tablet may require multiple tablets; 550mg strength is standard for this indication). IBS-D: 550 mg three times a day for 14 days, can be repeated.
Note: Administer with or without food. Tablet should be swallowed whole with a glass of water. For traveler's diarrhea, initiate at the first sign of diarrhea.
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 susceptible bacteria within the gastrointestinal lumen.
Pregnancy: Category C: Animal studies have shown adverse effects. No adequate and well-controlled studies in pregnant women. Use only if potential benefit justifies potential risk to the fetus.
Driving: May cause dizziness. Patients should be cautioned about operating machinery or driving until they know how the drug affects them.
| Cyclosporine | Rifaximin may potentially decrease cyclosporine efficacy by altering gut flora affecting its metabolism. Monitor cyclosporine levels. | Moderate |
| Warfarin | Theoretical interaction due to gut flora alteration affecting Vitamin K production. Monitor INR closely. | Moderate |
| Oral Contraceptives | No known pharmacokinetic interaction. However, in severe diarrhea, absorption may be impaired; advise backup contraception. | Low |