What is the recommended dose of Xifaxan (rifaximin) for hepatic encephalopathy and irritable bowel syndrome with diarrhea?

Recommended Dosing for Xifaxan (Rifaximin)

For hepatic encephalopathy, the recommended dose of Xifaxan is 550 mg taken orally twice daily, and for irritable bowel syndrome with diarrhea (IBS-D), the recommended dose is 550 mg taken orally three times daily for 14 days. 1, 2

Dosing for Hepatic Encephalopathy

• Dosage: 550 mg twice daily 2
• Duration: Long-term/continuous therapy 1
• Clinical context: Used as add-on therapy to lactulose for patients with recurrent hepatic encephalopathy episodes, or alone in patients who cannot tolerate lactulose 1
• Efficacy: Significantly reduces risk of breakthrough hepatic encephalopathy episodes (22.1% vs 45.9% with placebo) and hospitalizations involving hepatic encephalopathy (13.6% vs 22.6% with placebo) 3

Important considerations:

• Most patients in clinical trials (>90%) received concomitant lactulose therapy 3
• Patients with MELD scores >25 have not been extensively studied, and only 8.6% of patients in controlled trials had MELD scores over 19 1
• Alternative dosing: While some research has explored once-daily dosing 4, the FDA-approved and guideline-recommended dosage remains 550 mg twice daily 1, 2

Dosing for IBS-D

• Dosage: 550 mg three times daily 2
• Duration: 14 days 2
• Retreatment: Patients who experience symptom recurrence can be retreated up to two additional times with the same dosage regimen 1, 2
• Efficacy: Provides approximately 9% greater response rate compared to placebo (40.7% vs 31.7%) 5, 6

Important considerations:

• Positioned as a second-line treatment for IBS-D by both American Gastroenterological Association and British Society of Gastroenterology 1
• More effective for diarrhea symptoms than for abdominal pain 1
• Repeat treatment has been shown to be safe and effective in patients who initially respond but then relapse 6

Administration Guidelines

• Xifaxan can be taken with or without food 2
• Adverse events are generally comparable to placebo in clinical trials 7, 3, 6
• Common adverse events include ascites, dizziness, fatigue, peripheral edema, abdominal pain, diarrhea, headache, and upper respiratory tract infection 7

Clinical Pitfalls to Avoid

1. For hepatic encephalopathy: Don't use rifaximin as monotherapy in patients who can tolerate lactulose - the combination therapy is more effective 1, 3

2. For IBS-D: Don't exceed the 14-day treatment duration for initial therapy, and limit retreatment to no more than two additional courses 1, 2

3. For both indications: Be aware of increased systemic exposure in patients with severe hepatic dysfunction 1

4. For IBS-D: Set appropriate expectations with patients regarding the modest efficacy for abdominal pain relief compared to diarrhea symptoms 1