From the Guidelines
Rifaximin is recommended to be dosed at 550 mg taken orally three times daily for 14 days for the treatment of irritable bowel syndrome with diarrhea (IBS-D), with potential retreatment cycles for recurrent symptoms. This dosing regimen is based on the most recent and highest quality study, which is the 2022 AGA clinical practice guideline on the pharmacological management of IBS-D 1. The guideline suggests that patients who experience a recurrence of symptoms can be retreated up to 2 times with the same dosage regimen.
- Key points to consider when prescribing rifaximin include:
- The medication is a nonabsorbable, oral antibiotic with a broad spectrum of activity against both gram-negative and gram-positive anaerobic and aerobic bacteria.
- It is FDA-approved for the treatment of IBS-D at the specified dosage.
- Patients should complete the full prescribed course even if symptoms improve before completion.
- Common side effects include nausea, bloating, and headache, as noted in the study 1.
- It is essential to note that rifaximin works by inhibiting bacterial RNA synthesis and is minimally absorbed systemically, allowing it to act primarily in the gastrointestinal tract with few systemic side effects, as described in the guideline 1.
From the FDA Drug Label
The efficacy of XIFAXAN given as 200 mg orally taken three times a day for 3 days was evaluated in 2 randomized, multi‑center, double-blind, placebo-controlled studies in adult subjects with travelers’ diarrhea.
In addition, this study provided evidence that subjects treated with XIFAXAN with fever and/or blood in the stool at baseline had prolonged TLUS
The recommended dosing for Rifaximin is:
- 200 mg orally taken three times a day for 3 days for travelers’ diarrhea
- 550 mg orally administered three times a day for 7 days or 550 mg twice daily for other indications, as mentioned in the label 2, 2.
From the Research
Rifaximin Dosing
- The recommended dosing for Rifaximin varies depending on the condition being treated 3, 4, 5.
- For the prevention of hepatic encephalopathy, a dose of 550 mg twice daily for 6 months has been shown to be effective 3.
- For irritable bowel syndrome, a dose of 1650 mg per day for 2 weeks has been used in clinical trials 4.
- For travelers' diarrhea, doses of 200 mg per day, 200 mg twice daily, or 200 mg three times daily have been studied 6.
- The daily dose of Rifaximin can range from 600 mg (1 tablet 3 times a day) to 800 mg (2 tablets twice a day) 5.
Dosing Comparison
- A study compared once a day rifaximin to twice a day dosage in the prevention of recurrence of hepatic encephalopathy in patients with chronic liver disease, and found no significant difference between the two dosing regimens 7.
- The use of Rifaximin 1100 mg per day for 6 months has been reported to prevent 1 episode of hepatic encephalopathy for every 4 patients treated 4.
Dosage Forms and Solubility
- Rifaximin belongs to class IV according to the Biopharmaceutic Classification System (BCS), meaning that it is both poorly soluble and poorly permeable 5.
- Solubility of rifaximin can be improved by complexation to β-cyclodextrin, which can provide lower doses and facilitate compliance with pharmacotherapy 5.