Brand Name: Xifaxan
Generic Name: rifaximin

Drug Class: Rifamycin-derivative antibiotic
Manufacturer: Salix Pharmaceuticals
FDA Approval Date: May 27, 2015

What is Xifaxan and its mechanism of action?

Xifaxan (rifaximin) is an antibiotic derived from rifamycin and is similar to rifampin. Xifaxan kills bacteria in the gut by preventing production of proteins that bacteria need to survive and replicate. It is effective against Escherichia coli. Reducing bacteria in the gut reduces symptoms of irritable bowel syndrome associated diarrhea (IBS-D). Xifaxan is effective at relieving IBS symptoms associated with bacterial overgrowth in the intestine. Antibiotic-based therapy is a novel approach for treating IBS.

What are the uses for Xifaxan?

Xifaxan is used to treat:

•    Irritable bowel syndrome with diarrhea (IBS-D) (discussed in this monograph)

•    Traveler’s diarrhea

•    Hepatic encephalopathy

Irritable bowel syndrome (IBS) is a common gastrointestinal disease that affects 10-15% of the US population. IBS causes diarrhea (IBS-D), constipation (IBS-C), or mixed diarrhea and constipation (IBS-M). Common symptoms of IBS include abdominal pain or discomfort, bloating, gas, and bowel movement changes.

IBS is a functional disorder, meaning it has no known structural, infectious, or metabolic cause. IBS is associated with many factors including small intestine bacterial overgrowth (SIBO). Bacterial overgrowth may be responsible for excessive gas production and dietary malabsorption which results in bloating, abdominal pain, and diarrhea or constipation.

How effective is Xifaxan in controlling IBS-D?

In two studies 1260 patients with IBS without constipation were followed for 12 weeks and were assessed by relief of global IBS symptoms and relief of IBS-related bloating. Patients were treated for 14 days then observed for another 10 weeks. More patients (40.7%) in the Xifaxan group reported symptomatic relief than patients who received placebo (31.7%). In addition, 40.2% of patients experienced greater relief of bloating from treatment compared to 30.3% of placebo treated patients. 

Interesting facts about Xifaxan

Xifaxan is only taken for 2 weeks. If patients experience a recurrence of symptoms, they may be retreated up to two times with the same dosing regimen.

Xifaxan is an antibacterial agent, therefore, skipping doses or not completing the full course of therapy may decrease its efficacy and increase the risk of the bacteria developing resistance to the drug.

Xifaxan is also used for  treating traveler's diarrhea and hepatic encephalopathy.

What is the dosage of Xifaxan?

Xifaxan is available as 200 mg or 550 mg tablets.

The recommended dosing for IBS-D treatment is one 550 mg tablet by mouth three times a day for 14 days. Xifaxan may be taken with or without food. Patients with recurrence of symptoms may be retreated up to two times with the same regimen.

Store Xifaxan at room temperature between 68°F to 77°F.

What are side effects of Xifaxan?

Side effects of Xifaxan include: 

Peripheral edema

Nausea

Dizziness

Fatigue

Ascites

Muscle spasms

Abdominal pain

Elevated levels of liver enzymes

What are warnings and precautions for Xifaxan?

There are reports of Clostridium difficile-associated diarrhea (CDAD) from Xifaxan treatment. CDAD is associated with many antibiotic treatments due to changes in the intestinal flora. CDAD varies in severity from mild diarrhea to fatal colitis. CDAD is a medical emergency and requires discontinuation of the antibiotic therapy and hospitalization.

Inappropriate prescribing and poor adherence to Xifaxan therapy increase the risk of the development of drug-resistant bacteria.

Xifaxan has poor systemic bioavailability, however, there is increased systemic exposure in patients with severe hepatic impairment (Child-Pugh C).

Xifaxan is contraindicated in patients with hypersensitivity to rifaximin or rifamycin antibacterial agents. Hypersensitivity reactions include dermatitis, angioneurotic edema, and anaphylaxis.

What are Xifaxan drug interactions?

Cyclosporine, gemfibrozil, ketoconazole, and antiretrovirals may increase Xifaxan levels and the risk of adverse effects.

Can pregnant or breastfeeding women take Xifaxan?

Xifaxan has not been studied in pregnant women. Animal reproduction studies show that Xifaxan may cause fetal harm. Xifaxan should not be used during pregnancy.

Xifaxan has not been studied in women who are breastfeeding.

What is the cost of Xifaxan?

The average wholesale price for Xifaxan 550 mg is $33.62 per tablet. The manufacturer of Xifaxan, Salix Pharmaceuticals, offers a Xifaxan savings card for patients who need financial assistance.

Also Read

Description Of Irritable Bowel Syndrome (IBS) Symptoms

Viberzi (eluxadoline) Side Effects, Costs, Dosing, And Prescribing Information For Irritable Bowel Syndrome With Diarrhea (IBS-D)

Review of Medications for Ulcer Treatment and Prevention

Entyvio (vedolizumab) Cost, Dosing, Side Effects and Prescribing Information for Ulcerative Colitis and Crohn's Disease 

References

FDA approves two therapies to treat IBS-D. FDA. 27 May 2015. 

Irritable bowel syndrome: a global perspective. World Gastroenterology Organization. Apr 2009. 

Rifaximin in irritable bowel syndrome: rationale, evidence and clinical use. Therapeutic Advances in Chronic Diseases.

Rifaximin Therapy for Patients with Irritable Bowel Syndrome without Constipation. New England Journal of Medicine. 2011. 

XIFAXAN Prescribing Information (PI). Salix Pharmaceuticals. 

Rifaximin treatment for irritable bowel syndrome with a positive lactulose hydrogen breath test improves symptoms for at least 3 months. Alimentary Pharmacology & Therapeutics. Dec 2012. 

Drug Development and Drug Interactions.

REDBOOK Online.