Rifaxin550 mg

Rifaxin is a gut-selective (minimally absorbed) antibiotic with evidence-based indications that vary in strength:

Established / Approved Uses

• Traveler's diarrhea caused by noninvasive strains of Escherichia coli, in adults and children 12 years of age and older.
• Reduction in risk of recurrence of overt hepatic encephalopathy (HE) in adults, generally used together with lactulose rather than as monotherapy.
• Irritable bowel syndrome with diarrhea (IBS-D) in adults; repeat treatment courses may be given if symptoms recur.

Additional / Locally Recognized Use

• Small intestinal bacterial overgrowth (SIBO)-associated symptoms - commonly used in this setting in South Asian clinical practice, though this is not a core FDA-approved indication.

Rifaxin is not effective for diarrhea complicated by fever or blood in the stool, or diarrhea caused by pathogens other than E. coli; a physician should confirm the diagnosis before use.

Each film-coated tablet of Rifaximin generally contains Rifaximin INN 200 mg or 550 mg. An oral suspension formulation may also be available in some markets. Strengths and available dosage forms should be confirmed against the specific product label.

Rifaxin is a semi-synthetic, non-systemic antibiotic derived from rifamycin. It acts almost exclusively within the gastrointestinal lumen because less than 1% of an oral dose is absorbed into the bloodstream, which limits systemic side effects and drug interactions compared with absorbed antibiotics.

Rifaxin is used to treat traveler's diarrhea caused by certain strains of E. coli, to reduce the risk of recurrent episodes of hepatic encephalopathy, and to manage diarrhea-predominant irritable bowel syndrome.

Antibiotic - non-systemic (gut-selective) rifamycin derivative

Rifaximin inhibits bacterial DNA-dependent RNA synthesis by binding to the beta-subunit of bacterial RNA polymerase, thereby blocking transcription and protein synthesis. This gives it broad-spectrum activity against many gram-positive and gram-negative aerobic and anaerobic enteric bacteria.

Because Rifaximin is structurally modified to minimize absorption, more than 99% of an oral dose remains within the gastrointestinal tract and is excreted largely unchanged in the feces, so its antibacterial action is essentially local rather than systemic.

Take Rifaxin tablets by mouth, with or without food, at evenly spaced intervals. Swallow the tablet whole with a glass of water. Complete the full prescribed course even if symptoms improve early, unless a physician advises otherwise.

Rifaxin has few clinically significant interactions because of its minimal systemic absorption, but the following are well documented:

• P-glycoprotein (P-gp) inhibitors (e.g., cyclosporine): can substantially increase systemic exposure to Rifaxin; use with caution and monitor for adverse effects.
• Warfarin: changes in INR (both increases and decreases) have been reported in patients taking Rifaxin concomitantly with warfarin; monitor INR closely and adjust warfarin dose as needed.
• Other rifamycin antibiotics (e.g., rifampin): concomitant use is not recommended due to potential for cross-effects and possible cross-resistance.

Clinically significant induction of CYP3A4 by Rifaxin is unlikely at recommended doses in patients with normal liver function, but exposure may be higher and interaction risk greater in patients with hepatic impairment.

Side effects of Rifaxin vary somewhat by indication.

Common

• Headache
• Nausea and abdominal pain
• Flatulence and constipation
• Peripheral edema, dizziness, and fatigue (more common in hepatic encephalopathy treatment)
• Mild elevation of liver enzymes (ALT)

Less Common / Serious

• Urinary tract infection (reported with long-term use in hepatic encephalopathy)
• Clostridioides difficile-associated diarrhea (CDAD) - as with other antibiotics, though the risk is lower given minimal systemic absorption
• Hypersensitivity reactions including anaphylaxis, angioedema, and exfoliative dermatitis (see Contraindications)

Seek prompt medical attention for signs of a severe allergic reaction, severe or persistent diarrhea, or unusual bruising/bleeding.

Pregnancy: Animal reproduction studies have shown teratogenic effects at certain dose levels; there are no adequate, well-controlled studies of Rifaxin in pregnant women. Rifaxin should be used during pregnancy only if clearly needed and the potential benefit justifies the potential risk to the fetus. Consult a physician before use in pregnancy.

Lactation: It is not known whether Rifaxin is excreted in human breast milk. Because of minimal systemic absorption, transfer into milk is expected to be limited, but caution is advised; a physician should weigh the benefits of treatment against any potential risk to the breastfeeding infant.

Rifaxin is not effective for diarrhea complicated by fever or blood in the stool, or diarrhea caused by pathogens other than E. coli; if symptoms of invasive disease appear, an alternative antibiotic should be considered.

If diarrhea worsens or persists beyond 24-48 hours despite treatment, contact a physician - this may indicate an alternative pathogen or the development of C. difficile-associated diarrhea, which requires discontinuation of Rifaxin and appropriate treatment.

Hepatic impairment: Systemic absorption of Rifaxin is increased in patients with hepatic impairment, most markedly in severe (Child-Pugh Class C) disease. Use with caution in patients with severe liver impairment and monitor for adverse effects.

Antibiotic stewardship: Take exactly as prescribed by your physician; do not stop, extend, skip doses, or share this medicine with others without medical advice, to reduce the risk of antibiotic resistance and treatment failure.

There is no specific antidote for Rifaxin overdose. In case of suspected overdose, seek immediate medical attention or contact a poison control center/emergency services. Treatment is symptomatic and supportive; discontinue Rifaxin and manage symptoms under medical supervision.

Store at room temperature (below 30°C), away from light and moisture. Keep out of reach of children.

Renal impairment: No dose adjustment is generally required, as Rifaxin is minimally absorbed and predominantly eliminated in the feces; however, use with caution and physician guidance in significant renal impairment.

Hepatic impairment: See Precautions and Warnings - systemic exposure increases substantially with worsening hepatic function, especially Child-Pugh Class C; use with caution.

Elderly: No overall differences in safety or effectiveness have been observed between elderly and younger adult patients, but age-related decreases in hepatic, renal, or cardiac function should be considered.

Pregnancy and lactation: See Pregnancy and Lactation section.

Pediatric use: See Pediatric Uses section.

Duration of Rifaxin treatment depends on the indication: 3 days for traveler's diarrhea; long-term, physician-directed use for reducing hepatic encephalopathy recurrence; and 14 days per course for IBS-D (with up to 2 repeat courses if symptoms recur). Always follow the prescribing physician's instructions on duration.

Antibiotics > Rifamycins > Non-systemic (gut-selective) antimicrobials

Rifaximin binds to the beta-subunit of bacterial DNA-dependent RNA polymerase, blocking bacterial transcription and protein synthesis. Its chemical structure limits absorption from the gut, so this antibacterial action occurs mainly within the gastrointestinal lumen rather than systemically.

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Rifaxin is approved for traveler's diarrhea in children 12 years of age and older, using the same 200 mg three times daily, 3-day regimen as adults.

Safety and efficacy for reduction of hepatic encephalopathy recurrence and for IBS-D have not been established in patients younger than 18 years; use in these indications in children and adolescents is not recommended outside specialist guidance.