Toltrazuril — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	PO	10-30 mg/kg	q24h	Duration: 1-3 days, repeat after 7 days if needed Notes: Often used off-label; some protocols use 10 mg/kg once daily for 3 days.
Cat	PO	10-30 mg/kg	q24h	Duration: 1-3 days, repeat after 7 days if needed Notes: Off-label use; monitor for adverse effects.
Horse	PO	10-20 mg/kg	q24h	Duration: 3-5 days Notes: Limited data; use with caution.
Cattle	PO	15 mg/kg	single dose	Duration: Once Notes: For treatment of clinical coccidiosis; may be repeated after 5 days if severe.
Sheep/Goats	PO	20 mg/kg	single dose	Duration: Once Notes: For treatment of coccidiosis; may be repeated after 5 days.
Rabbit	PO	25-50 mg/kg	q24h	Duration: 2-3 days Notes: Often used off-label; monitor for GI upset.
Poultry (chickens, turkeys)	PO (in drinking water)	7 mg/kg (as 2.5% solution: 1 L per 1000 L drinking water)	q24h	Duration: 2 days Notes: Administer in drinking water for 2 consecutive days.
Exotic (reptiles, small mammals)	PO	10-30 mg/kg	q24h	Duration: 2-5 days Notes: Dose based on extrapolation; adjust based on species and severity.

Clinical Indications & Species Uses

General Indications

Treatment and prevention of coccidiosis in various domestic and exotic animals

Dog (Canine)

Treatment and prevention of coccidiosis caused by Isospora (Cystoisospora) species

Cat (Feline)

Treatment and prevention of coccidiosis caused by Isospora (Cystoisospora) species

Horse (Equine)

Treatment of coccidiosis caused by Eimeria species (less common)

Cattle (Bovine)

Treatment and prevention of coccidiosis caused by Eimeria bovis and Eimeria zuernii

Small Ruminants (Sheep / Goat)

Treatment and prevention of coccidiosis caused by Eimeria species (e.g., E. ovinoidalis, E. crandallis)

Rabbit & Small Mammals

Treatment and prevention of coccidiosis caused by Eimeria species (e.g., E. stiedae, E. intestinalis)

Avian & Poultry

Treatment and prevention of coccidiosis caused by Eimeria species (e.g., E. tenella, E. necatrix, E. acervulina) in chickens and turkeys

Exotic & Other Species

Treatment of coccidiosis in various exotic species (e.g., reptiles, small mammals) due to Eimeria or Isospora species

Pharmacology & Mechanism of Action

Drug Class: Triazinone anticoccidial | Pharmacological Group: Coccidiocidal

Mechanism of Action: Toltrazuril is a triazinone derivative that interferes with the respiratory chain enzymes of coccidian parasites, specifically inhibiting the mitochondrial electron transport and pyrimidine synthesis. It acts on all intracellular stages of coccidia (merozoites, schizonts, and gamonts), leading to disruption of the parasite's energy metabolism and cell division, ultimately causing parasite death.

Pharmacodynamics: Toltrazuril exhibits coccidiocidal activity against a broad spectrum of Eimeria and Isospora species. It is effective against both asexual and sexual stages of the parasite, which reduces oocyst shedding and environmental contamination. The drug has a prolonged effect due to its accumulation in tissues and slow elimination, providing a residual effect that helps prevent reinfection.

⚡ Pharmacokinetics Summary

Absorption: Toltrazuril is well absorbed after oral administration in most species. In poultry, absorption is rapid, with peak plasma concentrations reached within 24-48 hours. In mammals, absorption is also good, but bioavailability may vary depending on the formulation and fed state.

Distribution: Toltrazuril is widely distributed throughout the body, with high concentrations in the liver, kidneys, and intestinal tissues. It crosses the blood-brain barrier to a limited extent. It accumulates in tissues, which contributes to its prolonged action.

Metabolism: Toltrazuril is extensively metabolized in the liver to its sulfoxide metabolite, toltrazuril sulfone (ponazuril), which also has anticoccidial activity. The parent drug and metabolites undergo enterohepatic recirculation.

Excretion: Excretion occurs primarily via the feces, with a smaller amount eliminated in the urine. Due to enterohepatic recirculation and tissue binding, elimination is slow, with a terminal half-life of several days in most species.

Half-Life: Dog: ~2-3 days; Cat: ~2-3 days; Horse: ~2-4 days; Cattle: ~3-5 days; Poultry: ~2-4 days

Bioavailability: Oral bioavailability is high (approximately 70-90%) in most species, but may be reduced when administered with food in some animals.

Protein Binding: Approximately 90% bound to plasma proteins in most species.

Available Formulations & Strengths

Oral Solution 2.5% (25 mg/mL), 5% (50 mg/mL) (PO)

Oral Paste 15% (150 mg/g) (PO)

Oral Powder Various (e.g., 5%, 10%) (PO)

Injectable Solution 5% (50 mg/mL) (IM, SC)

Contraindications & Clinical Warnings

Contraindications:

Hypersensitivity to toltrazuril or any component of the formulation
Use in animals with severe hepatic or renal impairment (caution)
Do not use in lactating animals if milk is intended for human consumption (unless withdrawal times are observed)
Do not use in animals intended for breeding without veterinary assessment

Warnings & Clinical Precautions:

Use with caution in debilitated or dehydrated animals; ensure adequate hydration.
In food animals, observe withdrawal times to avoid residues.
In poultry, ensure proper mixing in drinking water to achieve accurate dosing.
May cause gastrointestinal upset in some animals; monitor for vomiting or diarrhea.
Safety in pregnant or lactating animals has not been fully established; use only when clearly needed.
Avoid use in animals with known hypersensitivity to triazinones.
For extra-label use in food animals, follow AMDUCA regulations and consult a veterinarian.

Adverse Effects & Reactions

Common:

Mild gastrointestinal upset (vomiting, diarrhea)
Loss of appetite
Lethargy

Serious / Severe:

Allergic reactions (angioedema, anaphylaxis)
Hepatotoxicity (rare)
Bone marrow suppression (rare)

Rare:

Neurological signs (ataxia, tremors)
Renal toxicity
Teratogenic effects (in laboratory animals)

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Other anticoccidials (e.g., amprolium, monensin)	Potential additive effects or antagonism; use with caution.	Moderate
Immunosuppressive drugs (e.g., corticosteroids)	May reduce the efficacy of toltrazuril due to impaired immune response.	Moderate
Drugs affecting hepatic enzymes (e.g., phenobarbital)	May alter metabolism of toltrazuril, affecting efficacy or toxicity.	Mild

Overdose & Toxicity Management

Signs of Toxicity:

Vomiting
Diarrhea
Ataxia
Tremors
Respiratory depression
Hepatic or renal failure (in severe cases)

Emergency Treatment Protocol: There is no specific antidote. Treatment is symptomatic and supportive. Induce emesis if recent ingestion and animal is conscious. Administer activated charcoal to reduce absorption. Provide fluid therapy to correct dehydration and electrolyte imbalances. Monitor hepatic and renal function. In severe cases, hospitalization and intensive care may be required.

Food Animal Withdrawal Times

🥩 Meat: 8 days🥛 Milk: 5 days🥚 Eggs: 0 days

Withdrawal times vary by country and formulation. For cattle: meat 8 days, milk 5 days. For poultry: meat 8 days, eggs 0 days (not approved for laying hens in some countries). Always follow local regulations and product label.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20-25°C (68-77°F), excursions permitted between 15-30°C (59-86°F).

Light Sensitivity: Light-sensitive — protect from direct exposure.

Handling & Special Conditions: Protect from light. Keep container tightly closed. Avoid freezing. Store in a dry place.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for use in poultry (chickens) and cattle in some countries; not FDA-approved for dogs, cats, or horses in the US (off-label use).

Extra-Label (Off-Label) Use: In the US, toltrazuril is not FDA-approved for all species; extra-label use in food animals requires a valid veterinary-client-patient relationship and observance of withdrawal times. In the EU, toltrazuril is approved for poultry and cattle with specific withdrawal periods.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Toltrazuril is a highly effective anticoccidial with a broad spectrum of activity. It is commonly used in poultry and cattle for the control of coccidiosis, and off-label in dogs, cats, and exotic species. The drug is well tolerated, but may cause mild GI upset. In food animals, strict adherence to withdrawal times is essential. For best results, treatment should be initiated early in the course of infection, and supportive care (hydration, nutrition) is important. In outbreaks, environmental sanitation and management practices are crucial to prevent reinfection. Toltrazuril is often preferred over other anticoccidials due to its coccidiocidal action and prolonged effect.

References & Literature

📚 Plumb's Veterinary Drug Handbook
📚 Papich Veterinary Pharmacology and Therapeutics
📚 Compendium of Veterinary Products (CVP)