Recommended Rifaximin Dosing for Various Conditions
For irritable bowel syndrome with diarrhea (IBS-D), the FDA-approved dosage of rifaximin is 550 mg three times daily for 14 days, with up to two retreatments using the same dosage regimen for recurrent symptoms. 1
Dosing for IBS-D
- Initial treatment: Rifaximin 550 mg orally three times daily for 14 days 1
- For patients who experience recurrence of symptoms after initial response: Retreatment with rifaximin 550 mg three times daily for 14 days (up to 2 additional treatment courses) 1
- Clinical trials have shown significant improvement in IBS-D symptoms including abdominal pain, bloating, and stool consistency with this dosing regimen 2
- Some research suggests higher doses (1100 mg twice daily for 10 days) may be effective for moderate to severe IBS-D, but this is not the FDA-approved regimen 3
Dosing for Hepatic Encephalopathy
- For reduction in risk of recurrence of overt hepatic encephalopathy: Rifaximin 550 mg orally twice daily 4, 5
- Long-term maintenance therapy (≥24 months) with rifaximin 550 mg twice daily has been shown to be safe and effective in preventing hepatic encephalopathy-related hospitalizations 6
- When used for hepatic encephalopathy, rifaximin is typically administered in combination with lactulose for optimal outcomes 4
- Alternative dosing used in some clinical settings: 400 mg three times daily (maximum dose 1,200 mg/day) 4
Dosing for Traveler's Diarrhea
- FDA-approved dosage: Rifaximin 200 mg orally three times daily for 3 days 7
- Clinical trials have also shown efficacy with rifaximin 400 mg twice daily for 3 days for traveler's diarrhea 8
- Rifaximin is particularly effective against Escherichia coli, the predominant pathogen in traveler's diarrhea 7
Dosing for Clostridium difficile Infection
- For second or subsequent recurrence of C. difficile infection in children: Vancomycin for 10 days followed by rifaximin 400 mg three times daily for 20 days 1
- Not FDA-approved for use in children <12 years of age 1
Important Considerations
- Rifaximin is a non-absorbable antibiotic that acts locally in the gastrointestinal tract with minimal systemic adverse effects 5
- For hepatic encephalopathy, combination therapy with lactulose provides complementary effects in reducing ammonia levels and improving symptoms 4
- The safety profile of rifaximin in clinical trials has been comparable to placebo, with the most common adverse events including abdominal pain, diarrhea, headache, and upper respiratory tract infection (occurring in <10% of patients) 5
- Long-term rifaximin use has not been associated with increased risk of infections, including C. difficile, or development of bacterial antibiotic resistance 6
Pitfalls to Avoid
- Rifaximin should not be used as monotherapy for hepatic encephalopathy; combining with lactulose provides better outcomes 4
- For IBS-D, patients should be managed based on clinical response to therapy rather than microbiologic response 7
- When treating traveler's diarrhea, rifaximin is effective primarily against non-invasive bacterial pathogens and may not be appropriate for bloody diarrhea or fever 7
- For patients with hepatic encephalopathy who cannot take medications orally, rifaximin is not appropriate as it requires oral administration 4