Nitazoxanide
**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FDA-approved as an oral paste (Navigator®) for Equine Protozoal Myeloencephalitis (EPM), though this product has been withdrawn from the US market.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.
Mecanismo: **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.
Dosificación por especie
- Cryptosporidia-associated diarrhea · 25 mg/kg PO q12-24h · PO · q12-24h · No drug is consistently effective. Diarrhea sometimes resolves after administration.
- Equine protozoal myeloencephalitis (EPM) caused by Sarcocystis neurona · Days 1-5: 25 mg/kg (11.36 mg/lb) PO once daily; Days 6-28: 50 mg/kg (22.72 mg/lb) PO once daily · PO · once daily · 28 days · Product has been withdrawn from the US market.
- Relapsing EPM · Extend the treatment regimen from 28 to 56 days · PO · once daily · 56 days · Potentially effective therapy for relapsing cases.
Las dosis son una referencia clínica para veterinarios colegiados. Confirme siempre con la ficha técnica vigente y el paciente individual.
Vías de administración
Contraindicaciones
- 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)
Efectos adversos
- 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)
Interacciones farmacológicas
- Highly protein-bound drugs with narrow therapeutic index · Use with caution; tizoxanide is >99% protein bound and may displace or be displaced by other highly bound drugs, potentially altering free drug concentrations.
Monitorización
- 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
Sobredosis
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.
La referencia de fármacos de VetSheet está destinada a veterinarios colegiados como apoyo a la decisión clínica, no sustituye el juicio profesional ni la ficha técnica vigente del fabricante.