Drug Monograph
Full clinical overview, indications, dosage references & safety notes.
Available forms3 forms · 3 strengths documentedShow all ↓
Oral solution for dilution in drinking water 25 mg/mL (2.5%) Baycox®Oral suspension 50 mg/mL (5%) Baycox®Combination oral suspension — toltrazuril 18 mg/mL with emodepside Procox®
Overview
Toltrazuril (Baycox®) is a triazinone antiprotozoal (anticoccidial) agent that may be considered as an alternative treatment for coccidiosis in dogs and cats. It has also been used to treat the oocyst shedding stage of toxoplasmosis in cats. Although approved for use in food animals in some countries, it is not commercially available in the United States and must be legally imported or compounded by a reputable pharmacy.
Toltrazuril appears to be relatively well tolerated, although its adverse effect profile in mammals has not been well described. It is slowly absorbed after oral administration, rapidly metabolized to its active sulfone derivative (ponazuril), and is primarily excreted in the feces.
Mechanism of Action (MOA): Toltrazuril inhibits protozoal enzyme systems – specifically those the parasite needs to produce energy – as well as cell division, and damages intracellular structures. It is active against all intracellular stages of coccidia, including schizonts and micro- and macrogamonts. It interferes with protozoal nuclear division and mitochondrial activity, damages wall-forming bodies in microgametes, and produces marked vacuolization of the protozoal endoplasmic reticulum. Toltrazuril has activity against Hepatozoon spp., Isospora spp., Sarcocystis spp., Toxoplasma spp., and all intracellular stages of Coccidia spp.
Indications
Toltrazuril is used primarily as an alternative antiprotozoal agent for the treatment of coccidial infections in dogs and cats. It may also be used against certain other protozoal infections, although its role varies depending on the organism and clinical condition.
- Coccidiosis (dogs and cats): Alternative treatment for coccidial infections caused by Isospora (Cystoisospora) spp. It stops both replication of the parasites and shedding of oocysts.
- Toxoplasmosis (cats): Treatment of the enteroepithelial (oocyst shedding) stage of Toxoplasma infection.
- American canine hepatozoonosis (dogs): Has activity against Hepatozoon spp. and may produce an initial clinical response; however, it does not eliminate the parasites completely, remission is usually transient, and other drugs – for example imidocarb, primaquine or doxycycline – are generally used for this infection.
Dosage (Reference)
Dog
In dogs, toltrazuril is used extra-label primarily for the treatment of coccidiosis. Published dosing recommendations are limited, and the triazine antiprotozoals have been used in very few dogs.
| Clinical use | Route | Dose | Frequency | Notes |
|---|---|---|---|---|
| Coccidiosis (extra-label) | PO | 10–30 mg/kg | q24h | Extra-label use. Give for 1 to 3 consecutive days; treatment may be continued for up to 6 consecutive days. |
| Coccidiosis (combination product) | PO | 9 mg/kg | Once | Repeat treatment only if oocyst shedding continues. This dose is based on a toltrazuril–emodepside oral suspension tested against Isospora canis and the Isospora ohioensis complex. If needed, the dose may be increased to 20 mg/kg. |
- Published dosing information is limited. One authorized presentation exists for dogs – an oral suspension combined with emodepside, available in the UK on a named-patient basis; every other regimen in the table above is extra-label.
Cat
In cats, toltrazuril has been used extra-label for coccidiosis and for the enteroepithelial (oocyst shedding) stage of toxoplasmosis; it is not authorized for use in cats, but appears to be effective.
| Clinical use | Route | Dose | Frequency | Notes |
|---|---|---|---|---|
| Enteroepithelial cycle (oocyst shedding) of toxoplasmosis (extra-label) | PO | 5–10 mg/kg | q24h | Extra-label use. Give for 2 days; longer treatment courses of 7 to 14 days may also be used. |
| Coccidiosis (extra-label) | PO | 20–30 mg/kg | Once | Repeat the single dose after 10 days to improve efficacy. Alternatively, give 30 mg/kg once daily for 2 to 3 days. |
| Coccidiosis in kittens (extra-label) | PO | 15 mg/kg | q24h | Give for 3 days, then repeat the course 10 days later. |
- Repeating the coccidiosis dose after 10 days improves efficacy.
Warnings & Precautions
Toltrazuril must not be used in patients with known hypersensitivity to triazinone antiprotozoals. Care should also be taken to avoid confusion with ponazuril, as the two drugs have different dosage recommendations.
- Hypersensitivity: Do not use in patients with a known hypersensitivity to toltrazuril or other triazinone (triazine) antiprotozoals (e.g., ponazuril, diclazuril).
- Drug identification: Do not confuse toltrazuril with toltrazuril sulfone (ponazuril), as the dosage recommendations differ.
- Environmental considerations: The principal metabolite (toltrazuril sulfone, ponazuril) may persist in the environment and contaminate groundwater through untreated manure. This risk is considered minimal when the drug is used in dogs, cats, or other companion animals.
- Pregnancy & lactation: Reproductive and nursing safety have not been established. Use only when the maternal benefits outweigh the potential risks to the offspring.
- Age and bodyweight: Do not use in animals under 2 weeks of age or weighing less than 0.4 kg.
Drug Interactions
No clinically significant drug interactions have been reported for toltrazuril itself. Where the combination product with emodepside is used, that component has its own interaction profile.
- None reported: No drug interactions were reported in the available veterinary literature.
Side Effects & Overdose
Side Effects
Toltrazuril appears to be well tolerated, although its adverse effect profile in mammals has not been well described.
- Gastrointestinal effects: Gastrointestinal signs may occur; occasional mild diarrhea and/or vomiting have been reported.
- General tolerability: Appears to be well tolerated in birds; information on adverse effects in mammals is limited.
- Related drug observations: Horses receiving the related drug ponazuril have developed blisters on the nose and mouth, as well as rash or hives during field trials.
Overdose
Toltrazuril has a wide apparent margin of safety. Management of overdose is primarily supportive.
- Safety margin: Doses up to 5 times the labeled recommendations in calves, lambs, and piglets produced no adverse hematologic or pathologic effects, and doses up to 10 times the labeled recommendations in horses were tolerated without significant adverse effects. Poultry also tolerated overdoses up to 5 times the labeled dose without clinical signs.
- Clinical signs: Decreased water intake has been reported when overdoses exceed 5 times the labeled recommendations.
- Management: Consultation with a veterinary poison control center is recommended for known or suspected overdoses.
Key Notes
Practical clinical points that help optimize the safe and effective use of toltrazuril in dogs and cats:
- Monitoring: Assess clinical efficacy by performing fecal egg count reduction testing before treatment and again 10 to 14 days after treatment; another current source instead gives a fecal flotation for Cystoisospora oocysts 1 to 2 weeks after treatment.
- Administration: May be given with or without food. If vomiting or gastrointestinal upset occurs when administered on an empty stomach, give future doses with food or a small treat.
- Handling: Avoid direct contact with the medication. Wear disposable gloves and wash hands after administration.
- Blanket treatment: In kennels, catteries and shelters the drug is used as a blanket (metaphylactic) treatment alongside a strict hygiene regime, rather than as treatment of an individual animal.
- Long-term management: Treatment of canine hepatozoonosis is palliative. No drug has been shown to clear the infection, most dogs need long-term therapy to stay in clinical remission, and trials of toltrazuril combinations have not eliminated parasitemia.
- Pharmacokinetics: Highest concentrations are found in the liver and there is little enterohepatic recirculation. Plasma half-life has been reported only in food-producing species and is long – 72 hours in calves, 170 hours in lambs and 51 hours in piglets.
- Product identification: The same drug is marketed under other names, including Cevauril®, Chanox® Multi, Tolracol® and Zorabel®, and the chemical is also written toltrazurilo or toltrazurilum – worth knowing when a product is being imported.
- Dispensing: Store in a tightly sealed container, protected from light, at room temperature; the 2.5% solution at or below 25°C (77°F) and the 5% oral suspension at or below 30°C (86°F). The stability of compounded formulations has not been evaluated.
