Recommended Rifaximin Dosing for Various Conditions
The recommended dose of rifaximin varies by condition: for irritable bowel syndrome with diarrhea (IBS-D), use 550 mg three times daily for 14 days; for hepatic encephalopathy, use 550 mg twice daily; and for traveler's diarrhea, use 200 mg three times daily for 3 days. 1, 2, 3
Dosing by Condition
Irritable Bowel Syndrome with Diarrhea (IBS-D)
- FDA-approved dosage is 550 mg three times daily for 14 days 1, 2
- For patients who experience recurrence of symptoms after initial response, up to two additional treatment courses using the same dosage regimen (550 mg three times daily for 14 days) are recommended 1, 2
- Clinical trials demonstrated significant improvement in IBS-D symptoms with this dosing regimen compared to placebo 1
Hepatic Encephalopathy
- For reduction in risk of recurrence of overt hepatic encephalopathy, the recommended dose is 550 mg orally twice daily 2, 4
- Alternative dosing used in some clinical settings is 400 mg three times daily (maximum 1,200 mg/day) 2, 5
- Rifaximin should be used in combination with lactulose for optimal management of hepatic encephalopathy 5
- In clinical trials, rifaximin 550 mg twice daily significantly reduced the risk of breakthrough episodes of hepatic encephalopathy compared to placebo (22.1% vs 45.9%) 4
Traveler's Diarrhea
- FDA-approved dosage is 200 mg orally three times daily for 3 days 3, 6
- Clinical studies demonstrated that rifaximin was as effective as ciprofloxacin for treating traveler's diarrhea 6
Special Considerations
Retreatment for IBS-D
- For patients with IBS-D who experience recurrence of symptoms after initial response, retreatment with rifaximin 550 mg three times daily for 14 days is recommended 1, 2
- Up to two additional treatment courses may be administered 1, 2
Combination Therapy for Hepatic Encephalopathy
- Rifaximin should not be used as monotherapy for hepatic encephalopathy 5
- Combination therapy with lactulose provides complementary effects in reducing ammonia levels and improving symptoms 5
- Clinical trials showed better recovery from hepatic encephalopathy with combination therapy compared to lactulose alone 5
Administration Considerations
- Rifaximin requires oral administration; it is not appropriate for patients who cannot take medications orally 5
- No dosage adjustment is specified for elderly patients, although greater sensitivity in some older individuals cannot be ruled out 3
Safety Profile and Monitoring
- Rifaximin has a favorable safety profile with minimal systemic absorption 7
- The most common adverse events in clinical trials for hepatic encephalopathy included ascites, dizziness, fatigue, and peripheral edema (10-15% of patients) 7
- For IBS-D, common adverse effects included abdominal pain, diarrhea, headache, and upper respiratory tract infection (<10% of patients) 7
- Monitor INR and prothrombin time in patients receiving concomitant warfarin, as changes in INR have been reported 3
- Exercise caution when using rifaximin concurrently with P-glycoprotein inhibitors such as cyclosporine, particularly in patients with hepatic impairment 3
Clinical Pearls
- Despite being an antibiotic, rifaximin has not been associated with Clostridium difficile infection in studies of patients treated for hepatic encephalopathy 8
- Rifaximin is a non-absorbable antibiotic that acts locally in the gastrointestinal tract, minimizing systemic adverse effects 7
- Higher doses of rifaximin (1100 mg twice daily for 10 days) have been studied for IBS-D with significant improvement in symptoms, though this is not the FDA-approved regimen 9