# Tinidazole: veterinary dose and monograph

> Tinidazole is a veterinary antibiotic. Second-generation nitroimidazole closely related to metronidazole, with a longer half-life (allowing less-frequent dosing) and often better GI tolerance. Indications include giardiasis (dogs and cats); anaerobic bacterial infections (with appropriate companion drugs); tritrichomonas foetus enteritis (cats — specialist use). This monograph lists 4 reference doses for dogs, cats and horses, each with route, frequency and source.

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

## At a glance

- **Drug class:** Antibiotic
- **Also known as:** Tiniba, Fasigyn, Tinvista
- **Species with doses:** Dogs, Cats and Horses
- **General dose range:** 15–30 mg/kg PO q12–24h — check the species tables for the indication
- **Routes:** PO
- **Last reviewed:** 1 October 2026

## Indications

- Giardiasis (dogs and cats)
- Anaerobic bacterial infections (with appropriate companion drugs)
- Tritrichomonas foetus enteritis (cats — specialist use)
- Amoebic / other protozoal infections

## Tinidazole 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

*Tinidazole doses for dogs*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Anaerobic infection / stomatitis | 15–25 mg/kg | PO | q12h | 7 days |
| Giardiasis | 15–44 mg/kg | PO | q12h (15 mg/kg) or q24h (44 mg/kg) | 5–6 days |

- Anaerobic infection / stomatitis: Papich 5e: 15 mg/kg q12h PO. Plumb’s p.1125 (Greene 2006): stomatitis and anaerobic infections 15–25 mg/kg PO q12h for 7 days.
- Giardiasis: Papich 5e: 15 mg/kg q12h PO — 5 days or less treats Giardia. Plumb’s p.1125 (Barr 2006): 44 mg/kg PO q24h for 6 days.

### Cats

*Tinidazole doses for cats*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Giardiasis / anaerobic infection | 15 mg/kg | PO | q24h | 5 days (Giardia) / 7+ days (anaerobes) |

- Giardiasis / anaerobic infection: Papich 5e: 15 mg/kg q24h PO — 5 days for Giardia, longer for anaerobic infections. Plumb’s p.1125 (Greene 2006): stomatitis/anaerobes 15 mg/kg PO q24h for 7 days.

### Horses

*Tinidazole doses for horses*

| Indication | Dose | Route | Frequency | Duration |
| --- | --- | --- | --- | --- |
| Anaerobic infection | 10–15 mg/kg | PO | q12h | — |

- Anaerobic infection: Papich 5e and Plumb’s p.1125 (Pyorala 1990): 10–15 mg/kg PO q12h.

## Contraindications

Significant hepatic impairment (hepatic metabolism). Pregnancy (especially first trimester — mutagenicity concerns of nitroimidazoles). Known nitroimidazole hypersensitivity / neurologic disease (high-dose neurotoxicity). Concurrent alcohol-containing products (disulfiram-like reaction in some species).

## Species-specific warnings

> **Caution:** Cats: Cats are sensitive to nitroimidazole neurotoxicity — keep doses/durations conservative and stop at the first neurologic sign.

## Adverse effects

- GI upset (less than metronidazole), metallic taste/hypersalivation
- Neurotoxicity (ataxia, nystagmus, seizures) at high dose / prolonged use
- Lethargy, anorexia
- Rare hepatotoxicity, neutropenia

## Drug interactions

- Alcohol / alcohol-containing vehicles: disulfiram-like reaction (some species)
- Warfarin: potentiated anticoagulation
- CYP inducers (phenobarbital): reduce levels; inhibitors raise them
- Other neurotoxic drugs: additive CNS risk

## Pregnancy and lactation

Avoid in pregnancy (nitroimidazole mutagenicity concerns), particularly early gestation.

## Monitoring

- Neurological status on higher doses / longer courses (vestibular signs = stop)
- GI tolerance and clinical/parasitological response
- Liver values on prolonged therapy
- Faecal recheck for Giardia/Tritrichomonas cure

## Toxicity and overdose

Like metronidazole, the dose-limiting toxicity is NEUROTOXICITY — cumulative high doses or prolonged courses cause central vestibular signs (ataxia, nystagmus, head tilt) and seizures. Generally better GI tolerated than metronidazole. Hepatic and rare haematologic effects with chronic use.

Management: Stop the drug for any neurologic signs — nitroimidazole neurotoxicity is often slow to resolve; supportive care and time are the mainstays, and diazepam has been reported to speed recovery of metronidazole-class neurotoxicity. Decontaminate large acute ingestions; supportive care, monitor liver values.

## Clinical pearls

- A once-daily, often better-tolerated alternative to metronidazole for Giardia and anaerobic infections
- Respect the nitroimidazole neurotoxicity ceiling — stop immediately at any ataxia/nystagmus and expect slow recovery (diazepam may help)
- Good tissue and CNS penetration suit anaerobic deep infections
- Avoid in pregnancy and in alcohol-containing co-medications

## Mechanism of action

A nitroimidazole pro-drug reduced inside anaerobic bacteria and protozoa (by ferredoxin-type low-redox systems) to reactive nitro radicals that damage microbial DNA, causing strand breakage and death. Aerobic mammalian cells do not reduce it, giving selectivity for anaerobes/protozoa. Its longer half-life than metronidazole permits less-frequent dosing.

## Formulations and products

- 300 mg tablet
- 500 mg tablet
- Oral suspension (compounded)
- Tiniba — 300 / 500 mg tablet, Tablet (human-label)
- Fasigyn — 300 / 500 mg tablet, Tablet (human-label)

## Storage

Tablets: 15–30 °C, dry, protect from light. Compounded suspension per pharmacy instructions.

## 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

- [Sulphadimidine (Sulfamethazine)](https://vetmasterji.com/drugs/sulphadimidine)
- [Tiamulin](https://vetmasterji.com/drugs/tiamulin)
- [Tildipirosin](https://vetmasterji.com/drugs/tildipirosin)
- [Tilmicosin](https://vetmasterji.com/drugs/tilmicosin)
- [Tobramycin](https://vetmasterji.com/drugs/tobramycin)
- [Trimethoprim / Sulfadiazine (TMP-Sulfa)](https://vetmasterji.com/drugs/tmp-sulfa)
- [Tulathromycin](https://vetmasterji.com/drugs/tulathromycin)
- [Tylvalosin](https://vetmasterji.com/drugs/tylvalosin)

## Frequently asked questions

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

Reference doses for Tinidazole in dogs: 15–25 mg/kg PO q12h for 7 days (Anaerobic infection / stomatitis); 15–44 mg/kg PO q12h (15 mg/kg) or q24h (44 mg/kg) for 5–6 days (Giardiasis). Confirm against the label and the patient before use.

### What is the dose of Tinidazole for cats?

Reference doses for Tinidazole in cats: 15 mg/kg PO q24h for 5 days (Giardia) / 7+ days (anaerobes) (Giardiasis / anaerobic infection). Confirm against the label and the patient before use.

### What is the dose of Tinidazole for horses?

Reference doses for Tinidazole in horses: 10–15 mg/kg PO q12h (Anaerobic infection). Confirm against the label and the patient before use.

### When should Tinidazole not be used?

Significant hepatic impairment (hepatic metabolism). Pregnancy (especially first trimester — mutagenicity concerns of nitroimidazoles). Known nitroimidazole hypersensitivity / neurologic disease (high-dose neurotoxicity). Concurrent alcohol-containing products (disulfiram-like reaction in some species).

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

GI upset (less than metronidazole), metallic taste/hypersalivation; Neurotoxicity (ataxia, nystagmus, seizures) at high dose / prolonged use; Lethargy, anorexia; Rare hepatotoxicity, neutropenia.

## 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.