Drug Monograph
Full clinical overview, indications, dosage references & safety notes.
Available forms1 form · 2 strengths documentedShow all ↓
Tablet 200 mg human-labelledTablet 550 mg human-labelled
Overview
Rifaximin (Xifaxan®) is a nonsystemic antimicrobial used in dogs to modify the intestinal microbiota and to manage selected gastrointestinal disorders. It has also been investigated for the management of hepatic encephalopathy.
In dogs with chronic enteropathy, rifaximin induced complete remission in 86% and partial remission in 14% of dogs, and was shown in one study to be as effective as metronidazole. Its clinical use remains limited because of its relatively high cost.
Mechanism of Action (MOA): Rifaximin inhibits bacterial protein synthesis by binding to the beta-subunit of bacterial DNA-dependent RNA polymerase.
Indications
Rifaximin is used in dogs for selected gastrointestinal disorders and for modulation of the intestinal microbiota.
- Chronic enteropathy: Management of chronic enteropathy and chronic diarrhea.
- Hepatic encephalopathy: May be used to help manage or reduce recurrence of hepatic encephalopathy.
- Gut microbiota modulation: Used orally to modify the intestinal microbial population.
- Bowel preparation before surgery: Used as part of bowel preparation before surgery in patients with extrahepatic bile duct obstruction, to acutely alter enteric flora and reduce translocation of opportunistic pathogens.
Dosage (Reference)
Dog
Rifaximin has been evaluated for the management of chronic enteropathy and was reported to be as effective as metronidazole in one clinical study.
| Clinical use | Route | Dose | Frequency | Notes |
|---|---|---|---|---|
| Chronic enteropathy | PO | 25 mg/kg | q12h | Administer for 21 days. |
| Hepatic encephalopathy | PO | 5 mg/kg | q12h or q24h | Veterinary utility data are lacking and optimal dosing has not been established. |
| Hepatic encephalopathy in acute hepatic failure | PR (rectal) | 5-10 mg/kg | q12h | Nonabsorbed antibiotic; alters enteric flora. |
| Bowel preparation before surgery (extrahepatic bile duct obstruction) | PO or high enema | 5-10 mg/kg | q12h | Given by mouth or by high enema. Experience with rifaximin in dogs and cats is limited. |
• In one study, rifaximin was reported to be as effective as metronidazole for chronic enteropathy.
• Dogs in the study also received metoclopramide and ranitidine during the first 15 days of treatment.
• Weekly cyanocobalamin injections were administered during the study period.
• Dogs were maintained on a limited diet consisting of boiled chicken and rice.
• The study did not include a control group to determine the contribution of these concurrent interventions to treatment outcome.
Warnings & Precautions
Rifaximin is generally well tolerated due to its limited systemic absorption, but certain patient populations may require additional caution.
- Hypersensitivity: Contraindicated in patients with known hypersensitivity to rifaximin or other rifamycin antimicrobials.
- Severe hepatic impairment: Systemic exposure may increase substantially in patients with severe hepatic impairment.
- P-glycoprotein inhibitors: Systemic exposure may be further increased when rifaximin is administered concurrently with P-glycoprotein inhibitors.
- Clostridium difficile infection: Use of rifaximin has been associated with the development of Clostridium difficile infection in humans.
- Bloody diarrhea or diarrhea with fever: Rifaximin is not appropriate for use in patients with bloody diarrhea or diarrhea accompanied by fever.
- Hypersensitivity reactions: Serious reactions including exfoliative dermatitis, rash, angioneurotic edema, urticaria, flushing, pruritus, and anaphylaxis have been reported, sometimes within 15 minutes of administration.
- Pregnancy and nursing: Safety has not been established in animals. Use only when maternal benefits outweigh potential risks to offspring.
Drug Interactions
Clinically significant drug interactions are considered unlikely because rifaximin has limited systemic absorption. However, the following interactions have been reported or are theoretically possible.
- Cyclosporine: May increase rifaximin exposure.
- CYP3A4 inhibitors (e.g., clarithromycin, fluoxetine, ketoconazole, verapamil): May increase rifaximin exposure.
- P-glycoprotein inhibitors (e.g., amiodarone, clarithromycin, itraconazole, verapamil): May increase rifaximin exposure.
- Live oral vaccines: Concurrent antibiotic administration may reduce the immunologic response to live oral vaccines.
- Warfarin: May reduce prothrombin time (PT) and anticoagulant effects.
Side Effects & Overdose
Side Effects
Rifaximin appears to be well tolerated, with reported adverse effects occurring infrequently.
- Peripheral edema: Reported in humans.
- Dizziness: Reported in humans.
- Fatigue: Reported in humans.
- Pruritus: Reported in humans.
- Anemia: Reported in humans.
- Nausea: Reported in humans.
Overdose
Because rifaximin is minimally absorbed after oral administration, clinically significant signs following overdose are considered unlikely.
- Clinical effects: Clinical signs following overdose are unlikely due to limited systemic absorption.
- Management: Gut decontamination is generally not considered necessary.
- Supportive care: Monitor the patient closely and provide symptomatic and supportive treatment as needed.
Key Notes
Practical clinical points for the use of rifaximin in dogs:
- Minimal systemic absorption: Serum rifaximin concentrations were undetectable in dogs following oral administration in a pharmacokinetic study.
- Local gastrointestinal activity: More than 95% of the administered drug is excreted unchanged in the feces.
- Comparable efficacy: In one study, rifaximin produced remission rates comparable to metronidazole in dogs with chronic enteropathy.
- Cost considerations: Clinical use may be limited because rifaximin is substantially more expensive than commonly used alternatives such as metronidazole or lactulose.
