rifaximin
Brand: Xifaxan
Prototype Drug
Drug Class: antibiotic (GI-specific)
Drug Family: antibiotic
Subclass: non-absorbed rifamycin antibiotic
Organ Systems: gastrointestinalinfectious-disease
Mechanism of Action
Rifamycin-class antibiotic with >99% local GI activity (minimal systemic absorption); inhibits bacterial RNA polymerase; primarily active against gram-positive and gram-negative enteric organisms.
bacterial RNA polymerase (beta subunit)
Indications
- traveler's diarrhea (non-invasive E. coli)
- hepatic encephalopathy prevention (secondary)
- IBS-diarrhea predominant (IBS-D)
Contraindications
- traveler's diarrhea with fever/bloody diarrhea (invasive pathogens)
- severe hepatic impairment
Adverse Effects
Common
- flatulence
- headache
- nausea
Serious
- peripheral edema (rare in HE use)
- Clostridium difficile (rare — low risk given non-systemic)
Pharmacokinetics (ADME)
| Absorption | <1% systemic absorption |
| Distribution | GI lumen |
| Metabolism | GI local, minimal systemic CYP3A4 |
| Excretion | fecal |
| Half-life | not applicable — GI local |
| Onset | 1-4 hours (luminal) |
| Peak | 1-4 hours |
| Duration | 8-12 hours |
| Protein Binding | minimally |
| Vd | minimal |
Nursing Considerations
- For HE prevention: 550 mg BID ongoing after first HE episode
- No systemic drug interactions (negligible absorption)
- Take with or without food
- RIFAXIMIN-alpha for IBS-D: 550 mg TID x14 days
Clinical Pearls
- PREVENT trial: rifaximin reduces overt hepatic encephalopathy recurrence by 58% vs placebo
- Minimal systemic absorption: safe profile, no significant drug interactions
Safety Profile
Pregnancy use-with-caution
Lactation use-with-caution
Renal Adjustment Not required
Hepatic Adjustment Required
TDM Not required
Guideline Update pending
Concordance Terms
Cross-referenced clinical concepts — click any term to see all content where it appears.