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rifaximin (Xifaxan, Fatroximin, Normix)

Tradename: Xifaxam Indications: 1) traveler's diarrhea (noninvasive Escherichia coli) 2) irritable bowel syndrome (IBS) [3,6], FDA-approved [7] 3) reduces recurrence of overt hepatic encephalopathy in patients with advanced liver disease [4] 4) small intestinal bacterial overgrowth Dosage: 1) 200 mg TID for 3 days (with or without food) [1] 2) 200 mg QD-TID for 2 weeks [2] 3) 550 mg TID for 2 weeks (IBS) [6] 4) hepatic encephalopathy: 550 mg BID [9] Tabs: 200 mg, 550 mg Pharmacokinetics: 1) not absorbed systemically (< 0.4%) 2) induces cyt P450 3A4, but drug is absorbed Adverse effects: - headache - peripheral edema - nausea, constipation - dizziness, fatigue, insomnia - urinary tract infection - anemia - pruritus - ascites - elevated serum ALT [9] Drug interactions: - warfarin (dosage adjustment may be needed to maintain target INR) [9] Mechanism of action: - inhibits bacterial RNA synthesis by binding to beta-subunit of bacterial DNA-dependent RNA polymerase Notes: - cost (2010) for prevention of hepatic encephalopathy about $1200/month [5]

Interactions

drug interactions

General

antiprotozoal agent rifamycin (rifamycin SV, Rifocin, Aemcolo)

Properties

MISC-INFO: pregnancy-category C

Database Correlations

PUBCHEM cid=72111

References

  1. Prescriber's Letter 11(7):38 2004 Detail-Document#: 200706 (subscription needed) http://www.prescribersletter.com
  2. Journal Watch 25(13):103, 2005 DuPont HL, Jiang ZD, Okhuysen PC, Ericsson CD, de la Cabada FJ, Ke S, DuPont MW, Martinez-Sandoval F. A randomized, double-blind, placebo-controlled trial of rifaximin to prevent travelers' diarrhea. Ann Intern Med. 2005 May 17;142(10):805-12. Summary for patients in: Ann Intern Med. 2005 May 17;142(10):I30. PMID: 15897530
  3. Pimentel M, Park S, Mirocha J, Kane SV, Kong Y. The effect of a nonabsorbed oral antibiotic (rifaximin) on the symptoms of the irritable bowel syndrome: a randomized trial. Ann Intern Med. 2006 Oct 17;145(8):557-63. Summary for patients in: Ann Intern Med. 2006,145(8):I24. PMID: 17043337 - Drossman DA. Treatment for bacterial overgrowth in the irritable bowel syndrome. Ann Intern Med. 2006 Oct 17;145(8):626-8. (No abstract) PMID: 17043344
  4. FDA NEWS RELEASE, March 24, 2010 FDA Approves New Use of Xifaxan for Patients with Liver Disease http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm206104.htm - Bass NM, Mullen KD, Sanyal A et al Rifaximin treatment in hepatic encephalopathy. N Engl J Med. 2010 Mar 25;362(12):1071-81 PMID: 20335583
  5. Prescriber's Letter 17(6): 2010 Rifaximin (Xifaxan) for Hepatic Encephalopathy Detail-Document#: 260608 (subscription needed) http://www.prescribersletter.com - Sidhu SS et al. Rifaximin improves psychometric performance and health-related quality of life in patients with minimal hepatic encephalopathy (The RIME Trial). Am J Gastroenterol 2011 Feb; 106:307. PMID: 21157444 - Bajaj JS et al. Rifaximin improves driving simulator performance in a randomized trial of patients with minimal hepatic encephalopathy. Gastroenterology 2011 Feb; 140:478. PMID: 20849805
  6. Pimentel M et al Rifaximin Therapy for Patients with Irritable Bowel Syndrome without Constipation N Engl J Med. 2011 Jan 6;364(1):22-32. PMID: 21208106 http://www.nejm.org/doi/full/10.1056/NEJMoa1004409 - Tack J Antibiotic Therapy for the Irritable Bowel Syndrome N Engl J Med. 2011 Jan 6;364(1):81-2. PMID: 21208112 http://www.nejm.org/doi/full/10.1056/NEJMe1011211
  7. FDA News Release. May 27, 2015 FDA approves two therapies to treat IBS-D http://www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm448328.htm
  8. NEJM Knowledge+ Gastroenterology
  9. HIGHLIGHTS OF PRESCRIBING INFORMATION XIFAXAN (rifaximin) tablets, for oral use https://shared.salix.com/globalassets/pi/xifaxan550-pi.pdf