Toltrazuril
1-methyl-3-[3-methyl-4-[4-(trifluoromethylthio)phenoxy]phenyl]-1,3,5-triazine-2,4,6-trione
Also known as: Baycox · Bay-Vi-9142 · Procox · toltrazurilo · toltrazurilum
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Dosing by species
🌎 NA — North America🌍 EU — Europe
Dogs
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Coccidiosis (Cystoisosporosis) prevention | 10-20 mg/kg PO one time | PO | once | 1 dose | 🌎 NA |
| Coccidiosis | 15 mg/kg PO once daily | PO | q24h | 3-6 days | 🌎 NA |
| Isospora spp. infections | 10-30 mg/kg PO once daily | PO | q24h | 1-3 days | 🌎 NA |
| Coccidiosis | 20 mg/kg PO once daily | PO | q24h | 3 days | 🌎 NA |
| Isospora spp. / Hepatozoon canis | 9-20 mg/kg | PO | once | Single dose; further treatment is only indicated if oocyst shedding persists | 🌍 EU |
- Coccidiosis (Cystoisosporosis) prevention: Administer to all puppies at 3-4 weeks of age to help prevent problems associated with intestinal coccidiosis.
- Isospora spp. / Hepatozoon canis: Standard dose is 9 mg/kg. Higher doses up to 20 mg/kg can be used if required.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Enteroepithelial cycle of toxoplasmosis (oocyst shedding) | 5-10 mg/kg PO once daily | PO | q24h | 2 days | 🌎 NA |
| Coccidiosis | 30 mg/kg PO once daily | PO | q24h | 2-3 days | 🌎 NA |
| Coccidiosis | 20 mg/kg PO once daily | PO | q24h | 3 days | 🌎 NA |
| Isospora spp. | 9-20 mg/kg | PO | once | Single dose; further treatment is only indicated if oocyst shedding persists | 🌍 EU |
- Isospora spp.: Not authorized for use in cats but appears to be effective. Standard dose is 9 mg/kg. Higher doses up to 20 mg/kg can be used if required.
Birds
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Coccidiosis in raptors | 7 mg/kg PO once daily | PO | q24h | 2-3 days | 🌎 NA |
Reptiles
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Parasitism in Bearded Dragons | 5-15 mg/kg PO once daily | PO | q24h | 3 days | 🌎 NA |
Sheep
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Ovine coccidiosis (Eimeria ovinoidalis) | 20 mg/kg PO once | PO | once | 1 dose | 🌎 NA |
- Ovine coccidiosis (Eimeria ovinoidalis): Controlled study comparing efficacy against diclazuril.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Toltrazuril is a triazinone (triazine) antiprotozoal agent primarily labeled for treating coccidiosis in poultry and swine in Europe. In companion animal medicine, it is utilized off-label as an alternative treatment for various protozoal infections.
Key Uses:
- Coccidiosis in dogs and cats
- Isospora or Hepatozoon infections
- Oocyst shedding stage of toxoplasmosis in cats
- Overwhelming parasitic loads in reptiles (e.g., Bearded Dragons)
Clinical Pearls:
- Toltrazuril is the parent compound to ponazuril (toltrazuril sulfone), which is more commonly used and available in the US.
- While it can induce excellent initial clinical responses in dogs with American canine hepatozoonosis (ACH), it cannot completely eliminate the parasites, and remission is usually transient.
- Regulatory Note: It is not commercially available in the USA and must be legally imported for compassionate use.
Mechanism of action
The exact mechanism of action is not completely understood, but as a triazinone derivative, it acts on all intracellular developmental stages of coccidia.
- Pathway: It appears to inhibit protozoal enzyme systems → disrupts the division of the nucleus and the activity of the mitochondria → impairs the respiratory metabolism of the parasite → protozoal death.
- It is rapidly metabolized in the liver to its active sulfone derivative, ponazuril.
Safety & warnings
Contraindications
- Known hypersensitivity to toltrazuril or other triazinone antiprotozoals (e.g., ponazuril, diclazuril)
- Puppies or kittens < 2 weeks of age
- Animals weighing < 0.4 kg
Adverse effects
- Generally well tolerated in birds
- Potential gastrointestinal upset in mammals
- Blisters on nose and mouth (extrapolated from ponazuril use in horses)
- Rash or hives (extrapolated from ponazuril use in horses)
- Mild diarrhoea
- Vomiting
Precautions
Use with caution in pregnant or lactating animals, as no reproductive or nursing safety information is available; weigh potential risks versus benefits. The principle metabolite persists in the environment and can contaminate groundwater, though the risk is considered minimal when used in companion animals.
Drug interactions
Frequently formulated together; no negative interactions known between the two, but refer to emodepside monograph for its specific interactions.
Monitoring
- Clinical efficacy (resolution of clinical signs, negative fecal tests)
- Fecal flotation to monitor for resolution of oocyst shedding
- Resolution of clinical signs (e.g., diarrhea)
Pharmacokinetics
Half-life
Absorption
About 50% absorbed after oral consumption in poultry.
Distribution
Highest concentrations are found in the liver.
Metabolism
Rapidly metabolized into the sulfone derivative (ponazuril).
Elimination
Excreted primarily in the feces, with a very long elimination half-life.
Overdose
Very limited information is available.
- Horses: Doses up to 10X were tolerated without significant adverse effects.
- Poultry: 5X overdoses have been tolerated without clinical signs. Decreased water intake has been observed if overdoses are greater than 5X.
Available products
Formulations
- 2.5% (25 mg/mL) oral solution
- 18 mg/ml oral suspension (formulated with emodepside)
Veterinary
- Baycox 2.5% Solution (25 mg/mL) (Available in Europe; None in the USA)
- Procox oral suspension (18 mg/ml toltrazuril + 0.9 mg/ml emodepside)
- Baycox (various concentrations for livestock, sometimes used off-label)
Regulatory status
Approved as Procox (combination with emodepside) for dogs.
POM-V. Available on a named patient basis in the UK.
No regulatory data for: 🇺🇸 US · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store the 2.5% solution at temperatures at 25°C or below. Dilutions in drinking water more concentrated than 1:1000 (1 mL of the 2.5% solution to 1 liter of water) may precipitate. After dilution, the resulting solution is stable for 24 hours. Discard medicated drinking water not consumed after 24 hours.
Client information
Safety Warning: Avoid direct contact with this medication. The manufacturer recommends wearing synthetic rubber gloves when handling the 2.5% solution. Wash exposed skin thoroughly after use.
- Administer exactly as directed by your veterinarian.
- If diluting the medication in drinking water, discard any medicated water that is not consumed within 24 hours.
VetSheet drug reference is intended for licensed veterinary professionals as a clinical decision-support aid, not a substitute for professional judgement or the manufacturer’s current label.