Nitazoxanide
Nitrothiazolyl-salicylamide derivative
Also known as: Alinia · Navigator · Daxon · Heliton · PH-5776 · desacetyl-nitazoxanide (active metabolite tizoxanide)
Reviewed by the VetSheet Veterinary TeamUpdated Apr 5, 2026Evidence-based veterinary reference
Audited v13 dosing evidence
Structured calculator evidenceGiardia spp associated diarrhea (extra-label)
Verified clinician required
- once
NA
Governing clinical context (1)
- The human-approved powder for oral suspension should be stored at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F-86°F). Once suspended with tap water, the oral suspension should be kept in tightly closed containers at room temperature and discarded after 7 days.
Cryptosporidia spp associated diarrhea (extra-label)
Verified clinician required
- once
NA
Governing clinical context (1)
- The human-approved powder for oral suspension should be stored at 25°C (77°F); excursions permitted to 15°C to 30°C (59°F-86°F). Once suspended with tap water, the oral suspension should be kept in tightly closed containers at room temperature and discarded after 7 days.
Doses are a clinical reference for licensed veterinary professionals. Always confirm against the current label and the individual patient.
Overview
Nitazoxanide is a broad-spectrum thiazolide antiparasitic and antibacterial agent.
Key clinical highlights:
- Broad Spectrum: Exhibits activity against a wide variety of protozoa (including Sarcocystis neurona, Giardia, Cryptosporidium), nematodes, trematodes, and anaerobic bacteria (e.g., Helicobacter pylori).
- Equine Use: Historically FDA-approved as an oral paste (Navigator®) for Equine Protozoal Myeloencephalitis (EPM), though this product has been withdrawn from the US market.
- Small Animal Use: There is considerable interest in its off-label use for refractory Cryptosporidium and Giardia infections in dogs and cats. However, its clinical utility in small animals is often limited by significant gastrointestinal adverse effects (especially in dogs).
- Human Use: FDA-approved for treating diarrhea caused by Cryptosporidium parvum and Giardia lamblia in humans, where it is generally very well tolerated.
Mechanism of action
Nitazoxanide acts as a prodrug and is rapidly converted into its active metabolites, tizoxanide and tizoxanide glucuronide.
- Mechanism: It inhibits the pyruvate:ferredoxin oxidoreductase (PFOR) enzyme-dependent electron transfer reactions.
- Pathway: Inhibition of PFOR → disruption of essential anaerobic energy metabolism → death of susceptible protozoa and anaerobic bacteria.
- Unlike nitroimidazoles (e.g., metronidazole), nitazoxanide does not appear to cause DNA damage, reducing its mutagenic potential.
Safety & warnings
Contraindications
- Horses less than 1 year of age
- Horses that are sick or debilitated for reasons other than EPM
- Use with extreme caution in stallions and horses predisposed to laminitis
- Animals with compromised renal or hepatic function (safety not established)
Adverse effects
- Horses: Fever, anorexia, lethargy/depression, decreased gut sounds, diarrhea/enterocolitis, colic, laminitis, head/limb edema
- Horses: 'Treatment crisis' (CNS inflammation secondary to dying protozoa)
- Dogs: Excessive salivation, vomiting, diarrhea (often therapy-limiting)
- Humans: Yellow discoloration of sclera (rare, reversible)
Precautions
Use with caution in animals with compromised renal or hepatic function. In horses, monitor closely for signs of enterocolitis (disruption of normal flora) and laminitis (stallions may be more prone). A 'treatment crisis' may occur in horses during the first two weeks of EPM therapy due to CNS inflammation from dying protozoa, which may require anti-inflammatory therapy. Not evaluated in horses weighing > 1200 lbs.
Drug interactions
Use with caution; tizoxanide is >99% protein bound and may displace or be displaced by other highly bound drugs, potentially altering free drug concentrations.
Monitoring
- Clinical efficacy (resolution of diarrhea or neurological signs)
- Weekly body weight
- Adverse reactions (GI upset, hypersalivation)
- If adverse reactions occur: Physical exam, CBC, serum albumin, total serum protein
Pharmacokinetics
Half-life
Absorption
Absorbed orally and rapidly converted to the active metabolite tizoxanide (desacetyl-nitazoxanide).
Distribution
More than 99% of tizoxanide is bound to plasma proteins.
Metabolism
Rapidly hydrolyzed to tizoxanide, which is further conjugated to tizoxanide glucuronide.
Elimination
Tizoxanide is excreted in the urine, bile, and feces; the glucuronide metabolite is secreted in the urine and bile.
Overdose
Information on acute toxicity is limited.
- Horses: Overdoses of 2.5X have been associated with fatalities. Doses of ~5X labeled dose caused anorexia, diarrhea, and lethargy within 4 days.
- Dogs/Cats: Oral LD50 is > 10 g/kg.
- Rats: Repeated doses of 450 mg/kg caused intense salivation and increased liver/spleen weights.
- Humans: Doses up to 4 grams have been taken without significant adverse effects.
Treatment: In the event of an overdose, observe the patient closely and provide supportive care.
Available products
Formulations
- Oral Tablets
- Powder for Oral Suspension
- Oral Paste (Veterinary - Withdrawn)
Veterinary
- Nitazoxanide oral paste (32%); Navigator® (FDA approval withdrawn; no longer marketed)
Human-labeled
- Nitazoxanide Oral Tablets: 500 mg; Alinia®
- Nitazoxanide Powder for Oral Suspension: 20 mg/mL (100 mg/5 mL after reconstitution); Alinia®
Regulatory status
No regulatory data for: 🇺🇸 US · 🇪🇺 EU · 🇬🇧 UK · 🇭🇰 HK · 🇹🇼 TW · 🇯🇵 JP · 🇰🇷 KR · 🇦🇺 AU
Storage & stability
Store the human-approved powder for oral suspension at 25°C (77°F); excursions permitted to 15-30°C (59-86°F). Once reconstituted with tap water, keep the oral suspension in tightly closed containers at room temperature and discard after 7 days.
Client information
Important Note for Pet Owners: Nitazoxanide is not commonly used in dogs and cats, and is considered an 'off-label' treatment in veterinary medicine.
- Side Effects: In dogs and cats, this medication can cause significant stomach upset, including excessive drooling (hypersalivation), vomiting, and diarrhea. If these occur, contact your veterinarian, as the medication may need to be stopped.
- Administration: Follow your veterinarian's exact dosing instructions. Do not adjust the dose without consulting them.
- Monitoring: Keep an eye on your pet's appetite, energy levels, and body weight during treatment.
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.