Rifaximin

# Rifaximin ## Overview - **Classification**: Gut-selective antibiotic, rifamycin derivative - **Mechanism**: Inhibits bacterial RNA synthesis by binding to bacterial DNA-dependent RNA polymerase. Its action is primarily localized to the gastrointestinal tract due to minimal systemic absorption. ## Primary Indications 1. **Hepatic Encephalopathy (HE)**: Reduction in risk of overt HE recurrence in adults. 2. **Irritable Bowel Syndrome with Diarrhea (IBS-D)**: Treatment of IBS-D in adults. 3. **Traveler's Diarrhea (TD)**: Caused by non-invasive strains of *Escherichia coli* in adults and adolescents aged ≥12 years. ## Adult Dosing ### Standard Dosing **Hepatic Encephalopathy (HE) Reduction of Recurrence** - **Dose**: **550 mg** - **Frequency**: Twice daily (BID) - **Route**: Oral - **Duration**: Long-term **Irritable Bowel Syndrome with Diarrhea (IBS-D)** - **Dose**: **550 mg** - **Frequency**: Three times daily (TID) - **Route**: Oral - **Duration**: 14 days - **Special Consideration**: May repeat up to 2 courses if symptoms recur. **Traveler's Diarrhea (TD)** - **Dose**: **200 mg** - **Frequency**: Three times daily (TID) - **Route**: Oral - **Duration**: 3 days ### Dose Adjustments - **Renal Impairment**: No dose adjustment needed due to minimal systemic absorption. - **Hepatic Impairment**: No dose adjustment needed. - **Elderly Patients**: No specific dose adjustment needed. ## Pediatric Dosing ### Neonates (0-28 days) - **Special Notes**: Not recommended. Safety and efficacy not established. ### Infants (1-12 months) - **Special Notes**: Not recommended. Safety and efficacy not established. ### Children (1-12 years) - **Special Notes**: Not recommended for HE or IBS-D. For TD, not approved below 12 years. ### Adolescents (13-18 years) **Traveler's Diarrhea (TD)** - **Dose**: **200 mg** - **Frequency**: Three times daily (TID) - **Route**: Oral - **Duration**: 3 days - **Maximum**: **600 mg/day** (same as adult) - **Special Notes**: For HE and IBS-D, rifaximin is not FDA-approved in this age group. ## Safety Information ### Contraindications - **Absolute**: Hypersensitivity to rifaximin, rifamycins, or any component. - **Absolute**: Diarrhea complicated by fever and/or bloody stools (suggests invasive pathogens). ### Common Adverse Effects - **Very Common (>10%)**: Peripheral edema, nausea, dizziness, fatigue (especially in HE studies). - **Common (1-10%)**: Flatulence, abdominal pain, constipation, headache, increased ALT/AST. - **Serious but Rare**: *Clostridioides difficile*-associated diarrhea (CDAD), angioedema. ### Key Drug Interactions - **P-gp inhibitors (e.g., cyclosporine)**: May increase systemic exposure of rifaximin. Monitor for adverse effects. - **Warfarin**: Though minimally absorbed, monitor INR closely if co-administered due to potential gut flora alteration affecting vitamin K. ## Monitoring & Follow-up - **Before Treatment**: Assess for fever or bloody stools in diarrhea. Baseline LFTs for HE. - **During Treatment**: Monitor for symptom improvement. Watch for new or worsening diarrhea. - **Clinical Signs**: Resolution of symptoms for TD/IBS-D. Reduced HE episodes. ## Clinical Pearls - 💡 **Tip 1**: Rifaximin's minimal systemic absorption targets GI issues, reducing systemic side effects. - 💡 **Tip 2**: For IBS-D, patients may receive up to two 14-day courses for symptom recurrence. - 💡 **Tip 3**: Not effective for invasive bacterial diarrhea (e.g., fever, bloody stools) or *C. difficile* infection. - 💡 **Tip 4**: Advise patients to complete the entire prescribed course, even if symptoms improve. > **⚠️ Important**: This information is for educational purposes only. Always consult current prescribing information, local guidelines, and clinical judgment before prescribing.