|Trade names||Xifaxan, Xifaxanta, Normix, Rifagut|
|ATC code||A07AA11 (WHO) D06AX11 (WHO) QG51AA06 (WHO) QJ51XX01 (WHO)|
|Biological half-life||6 hours|
|Chemical and physical data|
|Molar mass||785.879 g/mol|
|3D model (Jmol)||Interactive image|
|(what is this?)|
Rifaximin (trade names:RCIFAX, Rifagut, Xifaxan, Zaxine) is a semisynthetic antibiotic based on rifamycin. It has poor oral bioavailability, meaning that very little of the drug will be absorbed into the blood stream when it is taken orally. Rifaximin is used in the treatment of traveler's diarrhea, irritable bowel syndrome, and hepatic encephalopathy, for which it received orphan drug status from the U.S. Food and Drug Administration in 1998.
Rifaximin is licensed by the U.S. Food and Drug Administration to treat traveler's diarrhea caused by E. coli. Clinical trials have shown that rifaximin is highly effective at preventing and treating traveler's diarrhea among travelers to Mexico, with few side effects and low risk of developing antibiotic resistance. It is not effective against Campylobacter jejuni, and there is no evidence of efficacy against Shigella or Salmonella species.
Rifaximin may also be a useful addition to vancomycin when treating patients with relapsing C. difficile infections. Although exposure to rifamycins in the past may increase risk for resistance, so rifaximin should be avoided in such cases.
There was recently[when?] a pilot-study done on the efficacy of rifaximin as a means of treatment for rosacea, according to the study, induced by the co-presence of small intestinal bacterial overgrowth.
In the United States, rifaximin has orphan drug status for the treatment of hepatic encephalopathy. Although high-quality evidence is still lacking, rifaximin appears to be as effective as or more effective than other available treatments for hepatic encephalopathy (such as lactulose), is better tolerated, and may work faster. Hepatic encephalopathy is a debilitating condition for those with liver disease. Rifaximin is an oral medication taken three times daily that helps patients to avoid reoccurring hepatic encephalopathy. It has minimal side effects, prevents reoccurring encephalopathy and high patient satisfaction. Patients are more compliant and satisfied to take this medication than any other due to minimal side effects, prolong remission, and overall cost. Rifaximin helps patients avoid multiple readmissions from hospitals along with less time missed from work as well. Rifaximin should be considered a standard prescribed medication for those whom have episodes of hepatic encephalopathy.
The drawbacks to rifaximin are increased cost and lack of robust clinical trials for HE without combination lactulose therapy.
Mechanism of action
Rifaximin interferes with transcription by binding to the β-subunit of bacterial RNA polymerase. This results in the blockage of the translocation step that normally follows the formation of the first phosphodiester bond, which occurs in the transcription process.
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A 2011 study in patients with IBS (without constipation) indicated 11% showed benefits over a placebo. The study was supported by Salix Pharmaceuticals, the patent holder. A 2010 study in patients treated for hepatic cirrhosis with hospitalization involving hepatic encephalopathy resulted in 22% of the rifaxmin treated group experiencing a breakthrough episode of hepatic encephalopathy as compared to 46% of the placebo group. The majority patients were also receiving Lactulose therapy for prevention of hepatic encephalopathy in addition to Rifaximin. Rifaximin shows promising results, causing remission in up to 59% of people with Crohn’s disease and up to 76% of people with ulcerative colitis.
In the United States, Salix Pharmaceuticals holds a US Patent for rifaximin and markets the drug under the name Xifaxan, available in tablets of 200 mg and 550 mg. In addition to receiving FDA approval for traveler’s diarrhea and (marketing approved for) hepatic encephalopathy, Xifaxan received FDA approval for IBS in May 2015. No generic formulation is available in the US and none has appeared due to the fact that the FDA approval process was ongoing. If Xifaxan receives full FDA approval for hepatic encephalopathy it is likely that Salix will maintain marketing exclusivity and be protected from generic formulations until March 24, 2017. Price quotes received on February 21, 2013 for Xifaxan 550 mg in the Denver Metro area were between $23.57 and $26.72 per tablet. A price quote received on June 24, 2016 for Xifaxan 550 mg was $31.37 per tablet.
Rifaximin is approved in 33 countries for GI disorders. On August 13, 2013, Health Canada issued a Notice of Compliance to Salix Pharmaceuticals Inc. for the drug product Zaxine. In India it is available under the brand names Ciboz and Xifapill.
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