Tinidazole: veterinary dose and monograph

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

• 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

• 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

• 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

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

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)
• Tiamulin
• Tildipirosin
• Tilmicosin
• Tobramycin
• Trimethoprim / Sulfadiazine (TMP-Sulfa)
• Tulathromycin
• Tylvalosin

Frequently asked questions