# Rifaximin: veterinary dose and monograph

> Rifaximin is a veterinary antibiotic. A poorly-absorbed (gut-/locally-acting) rifamycin antibiotic with broad activity against Gram-positive, Gram-negative and anaerobic bacteria. Indications include bovine mastitis (intramammary) — broad local antibacterial cover; endometritis / metritis / retained-placenta-associated infection (intrauterine) in cattle/mares; hepatic encephalopathy — reduce gut ammoniagenic flora (oral, gut-local). This monograph lists 2 reference doses for dogs and cattle, each with route, frequency and source, plus meat and milk withdrawal periods for food animals.

Source: https://vetmasterji.com/drugs/rifaximin · Last reviewed: 2026-10-01

## At a glance

- **Drug class:** Antibiotic
- **Also known as:** Rifaximin, Sebozin (intramammary), Xifaxan
- **Species with doses:** Dogs and Cattle
- **Routes:** Intramammary, PO
- **Last reviewed:** 1 October 2026

## Indications

- Bovine mastitis (intramammary) — broad local antibacterial cover
- Endometritis / metritis / retained-placenta-associated infection (intrauterine) in cattle/mares
- Hepatic encephalopathy — reduce gut ammoniagenic flora (oral, gut-local)
- Topical wound/uterine infection management

## Rifaximin dose by species

Doses are per administration unless stated. mg/kg doses scale with body weight; per-animal, per-quarter and infusion-rate doses are shown as the reference writes them.

### Dogs

*Rifaximin doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Chronic enteropathy | 25 mg/kg | PO | q12h | 21 days |

- Chronic enteropathy: Plumb’s 10e p.1121 (extra-label): 25 mg/kg PO every 12 hours for 21 days was as effective as metronidazole. All dogs also received metoclopramide and ranitidine for 15 days, weekly cyanocobalamin and a limited diet, and the study had no control group. This is the only rifaximin dose in Plumb’s 10e; Papich 5e has no monograph.

### Cattle

*Rifaximin doses for cattle*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Mastitis (intramammary) | One intramammary tube per affected quarter, per label | Intramammary | per label (one tube/quarter, repeat) | — | Withdrawal NOT established — treat as extra-label |

- Mastitis (intramammary): Label-sourced — Papich 5e has no rifaximin monograph and Plumb’s 10e (pp.1121–1122) doses dogs only, with no intramammary regimen. Intramammary products differ (lactating vs dry-cow tubes); follow the local label for the regimen and milk/meat withdrawals.

### Horses

*Rifaximin doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| No reference dose for this species | Not established in Papich 5e or Plumb’s 10e — do not extrapolate from another species | — | — | — |

- No reference dose for this species: Papich 5e has no rifaximin monograph and Plumb’s 10e (pp.1121–1122) doses dogs only; no equine intrauterine product or dose is referenced.

### Buffalo

No buffalo-specific doses are on file, so buffalo are dosed as cattle.

*Rifaximin doses for buffalo*

| Indication | Dose | Route | Frequency | Duration | Withdrawal |
| --- | --- | --- | --- | --- | --- |
| Mastitis (intramammary) | One intramammary tube per affected quarter, per label | Intramammary | per label (one tube/quarter, repeat) | — | Withdrawal NOT established — treat as extra-label |

- Mastitis (intramammary): Label-sourced — Papich 5e has no rifaximin monograph and Plumb’s 10e (pp.1121–1122) doses dogs only, with no intramammary regimen. Intramammary products differ (lactating vs dry-cow tubes); follow the local label for the regimen and milk/meat withdrawals.

## Contraindications

Rifamycin hypersensitivity. Systemic infection requiring systemic therapy (it is not systemically absorbed). Observe food-animal withdrawal for intramammary/intrauterine use. Known hypersensitivity. (As a rifamycin, mind resistance — avoid monotherapy for systemic pathogens.)

## Species-specific warnings

> **Caution:** Cattle: Observe milk/meat withdrawal for intramammary use; insert tubes aseptically to avoid introducing environmental mastitis.

## Adverse effects

- Generally minimal (negligible systemic absorption)
- Local irritation (intramammary/intrauterine)
- Reddish discolouration of secretions (rifamycin colour)
- GI flora disturbance (oral)

## Drug interactions

- Negligible systemic interactions (not absorbed)
- Oral: reduces gut flora (theoretical effect on vitamin-K/other gut-flora-dependent processes)
- As a rifamycin, potential cross-resistance with rifampin

## Pregnancy and lactation

Local/gut use gives minimal systemic exposure (low risk); intrauterine use is part of reproductive management. Follow product label.

## Monitoring

- Local response (mastitis cure — SCC/culture; uterine clearance)
- Hepatic encephalopathy: neurologic status / blood ammonia (oral use)
- Milk/meat withdrawal compliance
- Aseptic technique for intramammary/intrauterine infusion

## Toxicity and overdose

Very low systemic toxicity owing to negligible absorption — effects are essentially local (irritation) plus harmless reddish discolouration of secretions/urine. The main caveats are resistance stewardship (rifamycin class) and observing food-animal withdrawal.

Management: Supportive only; no specific antidote needed given the wide margin/poor absorption. Manage local irritation symptomatically.

## Clinical pearls

- A "stays-where-you-put-it" antibiotic — broad local cover for mastitis (intramammary) and metritis/endometritis (intrauterine) with negligible systemic absorption
- Oral rifaximin acts only in the gut — a useful, well-tolerated option for hepatic encephalopathy (reduce ammoniagenic flora) alongside lactulose
- Expect harmless reddish discolouration of secretions (rifamycin) and observe withdrawal periods
- Steward the rifamycin class (cross-resistance with rifampin) — don't use as systemic monotherapy

## Mechanism of action

A rifamycin that binds the beta-subunit of bacterial DNA-dependent RNA polymerase, inhibiting transcription (RNA synthesis) — bactericidal across a broad Gram-positive/Gram-negative/anaerobic spectrum. Its key pharmacologic feature is very poor absorption, so it concentrates and acts at the site of application (mammary gland, uterus, gut lumen) with negligible systemic levels — giving local efficacy and an excellent safety profile.

## Formulations and products

- Intramammary / intrauterine preparation (veterinary)
- Topical / uterine gel
- 200 / 400 / 550 mg tablet (human, gut-local)
- Rifaximin intramammary/intrauterine (vet) (Various) — Rifaximin local preparation, Intramammary / intrauterine
- Xifaxan / Rifagut — 200 / 400 / 550 mg tablet, Tablet (gut-local) (human-label)

## Storage

Intramammary/intrauterine/oral products: 15–30 °C, protect from light; use intramammary tubes aseptically.

## Before you use this dose

> **Caution:** Reference doses for veterinary professionals. Confirm the dose against the product label, the patient’s condition, current guidance and local regulations before use; the attending veterinarian remains responsible for every clinical decision.

## Other antibiotics

- [Polymyxin B](https://vetmasterji.com/drugs/polymyxin-b)
- [Pradofloxacin](https://vetmasterji.com/drugs/pradofloxacin)
- [Procaine Penicillin G](https://vetmasterji.com/drugs/procaine-penicillin)
- [Rifampin](https://vetmasterji.com/drugs/rifampin)
- [Silver Sulfadiazine](https://vetmasterji.com/drugs/silver-sulfadiazine)
- [Spectinomycin](https://vetmasterji.com/drugs/spectinomycin)
- [Streptomycin (Dihydrostreptomycin)](https://vetmasterji.com/drugs/streptomycin)
- [Sulfadiazine](https://vetmasterji.com/drugs/sulfadiazine)

## Frequently asked questions

### What is the dose of Rifaximin for dogs?

Reference doses for Rifaximin in dogs: 25 mg/kg PO q12h for 21 days (Chronic enteropathy). Confirm against the label and the patient before use.

### What is the dose of Rifaximin for cattle?

Reference doses for Rifaximin in cattle: One intramammary tube per affected quarter, per label Intramammary per label (one tube/quarter, repeat) (Mastitis (intramammary)). Confirm against the label and the patient before use.

### Can Rifaximin be given to horses?

Not established in Papich 5e or Plumb’s 10e — do not extrapolate from another species (No reference dose for this species).

### What is the withdrawal period for Rifaximin?

Cattle, Intramammary (Mastitis (intramammary)): Withdrawal NOT established — treat as extra-label. Follow the product label and national regulations where they differ.

### When should Rifaximin not be used?

Rifamycin hypersensitivity. Systemic infection requiring systemic therapy (it is not systemically absorbed). Observe food-animal withdrawal for intramammary/intrauterine use. Known hypersensitivity. (As a rifamycin, mind resistance — avoid monotherapy for systemic pathogens.)

### What are the side effects of Rifaximin in animals?

Generally minimal (negligible systemic absorption); Local irritation (intramammary/intrauterine); Reddish discolouration of secretions (rifamycin colour); GI flora disturbance (oral).

## Sources

- Plumb's Veterinary Drug Handbook
- Merck Veterinary Manual, 11th edition
- Papich, Papich Handbook of Veterinary Drugs, 5th edition

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VetMasterJi is a clinical decision-support and education platform for veterinary professionals and students. It does not provide veterinary advice, diagnosis or treatment for specific animals. All drug doses, calculators and differentials are references that must be independently verified before clinical use; the attending registered veterinarian remains solely responsible for every clinical decision.