Tinidazole
1-[2-(ethylsulfonyl)ethyl]-2-methyl-5-nitroimidazole
Also known as: Tindamax · Estovyn-T · Fasigyn · Tiniba · Tiniameb · CP-12574 · tinidazolum
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 |
|---|---|---|---|---|---|
| Stomatitis, anaerobic infections | 15-25 mg/kg PO q12h | PO | q12h | 7 days | 🌎 NA |
| Giardiasis | 44 mg/kg PO q24h | PO | q24h | 6 days | 🌎 NA |
- Giardiasis: Potentially useful for trichomoniasis, amebiasis, and balantidiasis.
Cats
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Stomatitis, anaerobic infections | 15 mg/kg PO q24h | PO | q24h | 7 days | 🌎 NA |
| Tritrichomonas foetus (experimental) | 30 mg/kg PO once daily | PO | q24h | 14 days | 🌎 NA |
- Tritrichomonas foetus (experimental): Decreased fecal shedding but failed to eradicate infection in 2 of 4 cats.
Horses
| Indication | Dose | Route | Frequency | Duration | Region |
|---|---|---|---|---|---|
| Susceptible anaerobic infections | 10-15 mg/kg PO q12h | PO | q12h | — | 🌎 NA |
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Tinidazole is a second-generation 5-nitroimidazole antimicrobial and antiprotozoal agent, structurally and pharmacologically similar to metronidazole.
Key clinical highlights include:
- Extended Half-Life: Tinidazole has a longer duration of action compared to metronidazole, allowing for less frequent dosing (e.g., once daily in cats compared to twice daily for metronidazole).
- Anaerobic Efficacy: It exhibits excellent activity against obligate anaerobes, particularly Porphyromonas spp. found in canine gingiva, making it highly useful for severe dental and oral infections.
- Antiprotozoal Activity: It is utilized as an alternative treatment for Giardia, Entamoeba histolytica, Trichomonas, and Balantidium infections.
- Tritrichomonas foetus: While ronidazole is typically the drug of choice for feline T. foetus, tinidazole has been investigated as an alternative, though it may only suppress shedding rather than fully eradicate the organism in some cases.
Clinical Pearl: Because of its intensely bitter taste, compounding into capsules or heavily flavored suspensions is highly recommended, especially for feline patients who may hypersalivate or reject the medication.
Mechanism of action
Tinidazole is a prodrug that requires activation within susceptible organisms.
- Uptake: The drug diffuses into the target anaerobic bacteria or protozoa.
- Reduction: Inside the cell, the nitro group of tinidazole is reduced by electron-transport proteins (such as ferredoxin or nitroreductase enzymes) specific to anaerobic metabolism.
- DNA Disruption: This reduction → generates highly reactive, unidentified polar nitro radical anions → these radicals bind to and disrupt DNA and nucleic acid synthesis → leading to strand breakage and rapid cell death.
This mechanism makes it rapidly bactericidal, trichomonacidal, and amebicidal.
Safety & warnings
Contraindications
- Hypersensitivity to tinidazole or other 5-nitroimidazoles (e.g., metronidazole, ronidazole)
- Food-producing animals (prohibited use)
Adverse effects
- Vomiting
- Inappetence
- Diarrhea
- Neurotoxicity (ataxia, nystagmus, seizures)
- Hypersalivation (due to bitter taste)
Precautions
Use with caution in patients with hepatic dysfunction, as the drug is metabolized by the liver.
Use with extreme caution in animals susceptible to seizures or with pre-existing neurological disease, as 5-nitroimidazoles can cross the blood-brain barrier and cause neurotoxicity.
Black Box Warning (Human Label): Carcinogenicity has been seen in mice and rats treated chronically with metronidazole. Avoid unnecessary use and reserve for indicated conditions.
Reproductive/Nursing: Decreased fertility noted in male rats. Crosses the placenta (mutagenic potential; avoid in first trimester; FDA Category C). Distributed into maternal milk; use milk replacer if treating a nursing dam.
Drug interactions
May induce a disulfiram-like reaction (nausea, vomiting, cramps).
May decrease the metabolism of tinidazole and increase the likelihood of dose-related side effects.
May decrease the metabolism of tinidazole and increase the likelihood of dose-related side effects.
Tinidazole may increase the serum levels of cyclosporine.
Tinidazole may increase the serum levels of tacrolimus.
Tinidazole may increase the serum levels of fluorouracil and increase the risk of toxicity.
Tinidazole may increase lithium serum levels and increase the risk for lithium toxicity.
May antagonize the therapeutic effects of metronidazole (and presumably tinidazole).
May increase the metabolism of tinidazole thereby decreasing blood levels.
May increase the metabolism of tinidazole thereby decreasing blood levels.
May increase the metabolism of tinidazole thereby decreasing blood levels.
May prolong the prothrombin time (PT). Avoid concurrent use if possible; otherwise, intensify monitoring.
Monitoring
- Clinical efficacy in treating the infection
- Gastrointestinal tolerance
- Neurological signs (ataxia, nystagmus, seizures)
Pharmacokinetics
Half-life
Absorption
Practically completely absorbed after oral administration in dogs, cats, and horses.
Distribution
Apparent volume of distribution (Vd) is 0.66 L/kg in dogs and horses, and 0.54 L/kg in cats.
Metabolism
Metabolized by the liver.
Elimination
Dogs clear the drug about twice as fast as cats.
Overdose
Very limited information is available. In rodent studies, the oral LD50 was >3.6 g/kg (mice) and >2 g/kg (rats).
Treatment of acute overdoses is symptomatic and supportive.
- Decontamination: Gastric lavage or induction of emesis may be helpful if performed shortly after ingestion and the patient is neurologically appropriate.
- Clearance: Hemodialysis can remove approximately 43% of the drug in the body (based on human data) in a 6-hour session.
Available products
Formulations
- Tablets (scored)
Human-labeled
- Tinidazole Tablets (scored): 250 mg & 500 mg (Tindamax®, generic)
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store tinidazole tablets at controlled room temperature (20-25°C) protected from light.
Client information
- Administration: Give this medication with food to reduce stomach upset.
- Taste Warning: This medication is extremely bitter. Do not crush or break tablets unless instructed by your veterinarian, as the bad taste may cause your pet to drool excessively or refuse to eat.
- Alcohol Avoidance: Ensure your pet does not have access to any products containing alcohol while on this medication.
- When to Call the Vet: Contact your veterinarian if gastrointestinal signs (vomiting, lack of appetite, diarrhea) are severe or persist.
- Emergency Signs: Contact your veterinarian immediately if your pet shows signs of behavior changes, eyes darting back and forth (nystagmus), convulsions/seizures, or difficulty walking/climbing stairs (ataxia). These can be signs of drug toxicity.
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.