Dosing and uses of Xifaxan (rifaximin)
Adult dosage forms and strengths
tablet
- 200mg
- 550mg
Traveler's Diarrhea
200 mg PO q8hr for 3 days
Hepatic Encephalopathy
Maintenance of remission
550 mg PO q12hr
Irritable Bowel Syndrome
Indicated for irritable bowel syndrome with diarrhea (IBS-D) in adult men and women
550 mg PO q8hr for 14 days; recurrence of symptoms can be retreated with a 14 day treatment course, up to 2 times
Available in unit-dose package containing 42 tablets (ie, 2 week supply) for this indication
Pediatric dosage forms and strengths
tablet
- 200mg
- 550mg
Traveler's Diarrhea
<12 years: Safety and efficacy not established
≥12 years: 200 mg PO q8hr for 3 days, with or without food
Xifaxan (rifaximin) adverse (side) effects
>10%
Flatulence (11%)
1-10%
Headache (10%)
Rectal tenesmus (7%)
Abdominal pain (7%)
Defecation urgency (6%)
Nausea (5%)
Constipation (4%)
Pyrexia (3%)
Vomiting (2%)
Frequency not defined
Hypersensitivity reactions (including allergic dermatitis)
Pruritus
Rash
Warnings
Contraindications
Hypersensitivity to rifamycin antibiotics
Cautions
Not effective in diarrhea complicated by fever, hematochezia, or diarrhea due to pathogens other than Escherichia coli
Not effective against traveler's diarrhea due to Campylobacter jejuni
Clostridium difficile-associated diarrhea has been reported
Efficacy against traveler's diarrhea due to Shigella spp and Salmonella spp not proven
Discontinue if symptoms worsen or persist >24-48 hr
Possibility of pseudomembranous colitis
Monitor patients with severe hepatic impairment for increased systemic exposure
Coadministration with P-gp inhibitors substantially increases systemic exposure to rifaximin; coadministration of cyclosporine with rifaximin resulted in 83-fold and 124-fold increases in rifaximin mean Cmax and AUC in healthy subjects
Pregnancy and lactation
Pregnancy category: C
Lactation: Do not use if nursing or do not nurse
Pregnancy categories
A: Generally acceptable. Controlled studies in pregnant women show no evidence of fetal risk.
B: May be acceptable. Either animal studies show no risk but human studies not available or animal studies showed minor risks and human studies done and showed no risk.
C: Use with caution if benefits outweigh risks. Animal studies show risk and human studies not available or neither animal nor human studies done.
D: Use in LIFE-THREATENING emergencies when no safer drug available. Positive evidence of human fetal risk.
X: Do not use in pregnancy. Risks involved outweigh potential benefits. Safer alternatives exist.
NA: Information not available.
Pharmacology of Xifaxan (rifaximin)
Mechanism of action
Antimicrobial action is a result of binding to the beta-subunit of bacterial DNA-dependent RNA polymerase, resulting in inhibition of transcription
Hepatic encephalopathy: Inhibits growth of enteric ammonia-producing bacteria to indirectly reduce serum ammonia leveL
Irritable bowel syndrome with diarrhea: The exact mechanism of action for IBS-D is not known, but is thought to be related to changes in the bacterial content in the gastrointestinal tract and reduction of gas
Absorption
Bioavailability: <0.4%
Peak plasma time: 1 hr
Distribution
Gut: 80-90%
Metabolism
Induces CYP3A4 in hepatocytes in vitro
Elimination
Half-life: 2-5 hr
Excretion: Feces (>90%)
Administration
Instructions
May take with or without food
