1. Clinical Overview
Rifaximin is a semi-synthetic, non-systemic antibiotic derived from rifamycin SV. It acts locally in the gastrointestinal tract with minimal systemic absorption (<1%). It is a first-line therapy for traveler's diarrhea and hepatic encephalopathy in India, valued for its targeted action, low resistance development, and favorable safety profile.
| Onset | Duration | Bioavailability |
|---|---|---|
| Clinical improvement in diarrhea symptoms is typically observed within 24-48 hours of starting therapy. | The local antibacterial effect persists for the duration of the dosing interval (typically 8-12 hours). Systemic effects are negligible. | < 0.4% (orally, due to poor absorption). |
2. Mechanism of Action
Rifaximin binds to the beta-subunit of bacterial DNA-dependent RNA polymerase, resulting in inhibition of bacterial RNA synthesis. This bactericidal action is specific to prokaryotic cells, sparing human RNA polymerase.
3. Indications & Uses
- Traveler's Diarrhea caused by non-invasive strains of Escherichia coli
- Reduction in risk of overt Hepatic Encephalopathy recurrence in adults
4. Dosage & Administration
Adult Dosage: Traveler's Diarrhea: 400 mg orally three times a day for 3 days. Hepatic Encephalopathy: 400 mg orally three times a day. IBS-D: 400 mg orally three times a day for 14 days, may be repeated.
Administration: Tablet to be taken with or without food. Swallow whole with a glass of water. For traveler's diarrhea, it may be taken with loperamide for symptom relief if no fever or bloody stools.
5. Side Effects
Common side effects may include:
- Peripheral edema
- Flatulence
- Headache
- Dizziness
- Nausea
- Abdominal pain
- Ascites (in cirrhosis patients)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Cyclosporine | Rifaximin may decrease cyclosporine levels; monitor levels closely. | Moderate |
| Warfarin | Theoretical potential for altered INR due to gut flora changes; monitor INR. | Moderate |
| Oral Contraceptives | No direct interaction, but if severe diarrhea/vomiting occurs, efficacy may be reduced. | Moderate |
7. Patient Counselling
- Complete the full prescribed course even if you feel better.
- Inform your doctor if diarrhea worsens or persists beyond 24-48 hours of treatment.
- Do not use to treat diarrhea with fever or blood/mucus in stools.
- Take with or without food as directed.
8. Toxicology & Storage
Overdose: Unlikely to cause systemic toxicity due to poor absorption. Potential symptoms may include nausea, vomiting, abdominal pain, and diarrhea.
Storage: Store below 30°C. Protect from moisture. Keep in the original blister pack until use. Keep out of reach of children.