Niclosamide — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	PO	50 mg/kg (up to 200 mg/kg for Echinococcus)	Single dose	Duration: One day; may repeat in 2-3 weeks if needed Notes: Administer on an empty stomach for best efficacy. For Echinococcus, higher doses may be required.
Cat	PO	50 mg/kg	Single dose	Duration: One day; may repeat in 2-3 weeks if needed Notes: Administer on an empty stomach. Tablets may be crushed and mixed with food.
Horse	PO	50-100 mg/kg	Single dose	Duration: One day Notes: Administer via stomach tube or oral paste. Fasting before treatment may improve efficacy.
Cattle	PO	50 mg/kg	Single dose	Duration: One day Notes: Administer as a drench or in feed. Withdrawal times must be observed.
Sheep/Goat	PO	50 mg/kg	Single dose	Duration: One day Notes: Administer as a drench or in feed.
Poultry	PO	50-100 mg/kg	Single dose	Duration: One day Notes: Administer in feed or water. Ensure adequate intake.

Clinical Indications & Species Uses

General Indications

Treatment of cestode infections in various domestic and wild animals.

Dog (Canine)

Treatment of tapeworm infections caused by Dipylidium caninum, Taenia spp., and Echinococcus spp.

Cat (Feline)

Treatment of tapeworm infections caused by Dipylidium caninum, Taenia taeniaeformis, and Echinococcus spp.

Horse (Equine)

Treatment of tapeworm infections caused by Anoplocephala perfoliata and other Anoplocephala spp.

Cattle (Bovine)

Treatment of tapeworm infections caused by Moniezia spp.

Small Ruminants (Sheep / Goat)

Treatment of tapeworm infections caused by Moniezia spp. in sheep and goats.

Avian & Poultry

Treatment of tapeworm infections in poultry (e.g., Raillietina spp., Davainea spp.)

Exotic & Other Species

Treatment of tapeworm infections in some exotic animals (e.g., reptiles, small mammals) under veterinary guidance.

Pharmacology & Mechanism of Action

Drug Class: Anthelmintic | Pharmacological Group: Salicylanilide derivative

Mechanism of Action: Niclosamide inhibits oxidative phosphorylation in the mitochondria of cestodes (tapeworms). It uncouples oxidative phosphorylation, leading to a decrease in ATP production and an increase in anaerobic metabolism. This disrupts the parasite's energy metabolism, causing paralysis and death of the tapeworm. The dead worm is then digested in the host's intestinal tract or passed in feces.

Pharmacodynamics: Niclosamide is selectively toxic to cestodes and some trematodes. It acts on the scolex and proglottids, causing them to detach from the intestinal wall. The drug has no effect on nematodes (roundworms) or other intestinal parasites. Its action is rapid, with effects seen within hours of administration.

⚡ Pharmacokinetics Summary

Absorption: Niclosamide is poorly absorbed from the gastrointestinal tract. The majority of the drug remains in the intestinal lumen, where it exerts its anthelmintic effect. Systemic absorption is minimal, with less than 10% of the administered dose being absorbed.

Distribution: Due to poor absorption, systemic distribution is negligible. The small amount that is absorbed is distributed in the plasma and tissues, but concentrations are low and not clinically significant.

Metabolism: The absorbed fraction is metabolized in the liver, primarily to inactive metabolites. The metabolism is rapid, and the metabolites are excreted in the urine.

Excretion: The unabsorbed drug is excreted in the feces. The absorbed portion is metabolized and excreted in the urine. The elimination half-life is short, but due to local action, systemic half-life is not clinically relevant.

Half-Life: Not well-defined; systemic half-life is short (minutes to hours) due to rapid metabolism and excretion, but local intestinal action persists.

Bioavailability: Oral bioavailability is very low (<10%) due to poor absorption.

Protein Binding: Not well-characterized; due to minimal systemic absorption, protein binding is not clinically significant.

Available Formulations & Strengths

Oral Tablet 500 mg, 1 g (PO)

Oral Powder Various concentrations (PO)

Oral Suspension Various concentrations (PO)

Contraindications & Clinical Warnings

Contraindications:

Hypersensitivity to niclosamide or any component of the formulation.
Do not use in animals with known intestinal obstruction or severe gastrointestinal disease.
Not recommended for use in animals with severe hepatic or renal impairment (though systemic absorption is minimal).

Warnings & Clinical Precautions:

Use with caution in debilitated or severely parasitized animals; may cause gastrointestinal upset.
For Echinococcus infections, strict hygiene measures should be followed to prevent human infection (zoonotic risk).
In food animals, observe withdrawal times.
Do not use in animals intended for breeding without veterinary consultation.
Pregnancy: Safe use has not been established; use only when clearly needed.

Adverse Effects & Reactions

Common:

Mild gastrointestinal upset (vomiting, diarrhea, anorexia)
Salivation (especially in cats)

Serious / Severe:

Rarely, severe gastrointestinal distress
Allergic reactions (urticaria, angioedema)

Rare:

Neurotoxicity (with massive overdose)
Hepatotoxicity (with systemic absorption)

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Other anthelmintics (e.g., praziquantel)	May have additive effects; combination therapy may be used for mixed infections.	Mild
Corticosteroids	May reduce the efficacy of niclosamide by stabilizing parasite mitochondria.	Moderate
Antacids or drugs that increase gastric pH	May reduce absorption and efficacy; separate administration by 2 hours.	Mild

Overdose & Toxicity Management

Signs of Toxicity:

Vomiting
Diarrhea
Abdominal pain
Lethargy
In severe cases, seizures or respiratory depression

Emergency Treatment Protocol: Treatment is symptomatic and supportive. Induce vomiting if recent ingestion and animal is conscious. Administer activated charcoal to reduce absorption. Provide fluid therapy and monitor for electrolyte imbalances. In severe cases, provide respiratory support and anticonvulsants if seizures occur.

Food Animal Withdrawal Times

🥩 Meat: 7 days🥛 Milk: 4 days🥚 Eggs: 7 days

Withdrawal times may vary by country and formulation; consult local regulations. For cattle, sheep, goats, and poultry, observe withdrawal periods for meat, milk, and eggs.

Storage, Handling & Regulatory Information

Storage Temperature: Store at room temperature (15-30°C / 59-86°F)

Handling & Special Conditions: Protect from moisture. Keep container tightly closed.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for use in dogs, cats, and some food animals (cattle, sheep, goats) in certain formulations. Not all formulations are approved in all species.

Extra-Label (Off-Label) Use: In the US, extra-label use in food animals is permitted under AMDUCA with veterinary oversight, but withdrawal times must be extended. In the EU, use in food animals may be restricted; consult a veterinarian.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Niclosamide is a highly effective and safe anthelmintic for tapeworm infections when used appropriately. It is poorly absorbed, so systemic side effects are rare. However, it is not effective against nematodes or other intestinal parasites. For mixed infections, combination therapy with other anthelmintics may be necessary. In dogs and cats, it is often used for Dipylidium caninum, which is transmitted by fleas, so flea control is essential to prevent reinfection. For Echinococcus infections, strict hygiene is crucial due to zoonotic potential. In horses, it is used for Anoplocephala perfoliata, which can cause colic. Always confirm the diagnosis and follow label directions or veterinary guidance. In food animals, adhere to withdrawal times to ensure food safety.

References & Literature

📚 Plumb's Veterinary Drug Handbook
📚 Papich Veterinary Pharmacology and Therapeutics
📚 Compendium of Veterinary Products (CVP)