Febantel — Veterinary Vademecum Drug Reference

Dosage & Administration Guidelines

Species	Route	Dose	Frequency	Duration & Clinical Notes
Dog	PO	10-15 mg/kg	q24h	Duration: 3 consecutive days Notes: For tapeworms, may need higher dose or extended duration. Often used in combination with praziquantel and pyrantel.
Cat	PO	10-15 mg/kg	q24h	Duration: 3 consecutive days Notes: Use with caution in kittens; safety not established under 6 weeks.
Horse	PO	6 mg/kg	q24h	Duration: Single dose or 5 consecutive days for encysted small strongyles Notes: For tapeworms, use 10 mg/kg for 5 days or as directed.
Cattle	PO	7.5 mg/kg	q24h	Duration: Single dose Notes: For lungworms, may repeat after 14 days.
Sheep/Goat	PO	5-10 mg/kg	q24h	Duration: Single dose Notes: Dose may vary by formulation; check label.
Rabbit	PO	20 mg/kg	q24h	Duration: 5 days Notes: Limited data; use with caution.

Clinical Indications & Species Uses

General Indications

Broad-spectrum anthelmintic for nematode and cestode infections in domestic animals.

Dog (Canine)

Treatment of gastrointestinal nematodes (roundworms, hookworms, whipworms)
Treatment of tapeworms (Taenia spp.)
Treatment of lungworms (Oslerus osleri)

Cat (Feline)

Treatment of gastrointestinal nematodes (roundworms, hookworms)
Treatment of tapeworms (Taenia spp.)

Horse (Equine)

Treatment of gastrointestinal nematodes (strongyles, ascarids, pinworms)
Treatment of tapeworms (Anoplocephala spp.)

Cattle (Bovine)

Treatment of gastrointestinal nematodes (Ostertagia, Cooperia, Haemonchus)
Treatment of lungworms (Dictyocaulus viviparus)

Small Ruminants (Sheep / Goat)

Treatment of gastrointestinal nematodes (Teladorsagia, Haemonchus, Trichostrongylus)
Treatment of lungworms (Dictyocaulus filaria)

Rabbit & Small Mammals

Treatment of gastrointestinal nematodes (Passalurus ambiguus)

Pharmacology & Mechanism of Action

Drug Class: Anthelmintic | Pharmacological Group: Benzimidazole prodrug

Mechanism of Action: Febantel is a prodrug that is metabolized to fenbendazole and oxfendazole, which are benzimidazole anthelmintics. The active metabolites bind to tubulin and inhibit microtubule polymerization, disrupting glucose uptake and energy metabolism in susceptible parasites, leading to their death. It is effective against nematodes and some cestodes.

Pharmacodynamics: Febantel exhibits a broad spectrum of anthelmintic activity against gastrointestinal nematodes, lungworms, and some tapeworms. It is ovicidal and larvicidal against many nematode species. The drug is more potent against adult stages but also affects larval stages. Its activity is time-dependent, requiring adequate exposure to the parasite.

⚡ Pharmacokinetics Summary

Absorption: Febantel is poorly absorbed from the gastrointestinal tract. After oral administration, a significant portion remains in the gut lumen to act locally. The absorbed fraction undergoes rapid metabolism.

Distribution: The absorbed febantel and its metabolites distribute widely in tissues, but concentrations are highest in the liver and kidneys. It crosses the blood-brain barrier to a limited extent.

Metabolism: Febantel undergoes extensive first-pass metabolism in the liver to fenbendazole and oxfendazole, which are the active anthelmintic metabolites. Further metabolism includes sulfonation and hydroxylation.

Excretion: The drug and its metabolites are primarily excreted in feces via bile, with a smaller amount excreted in urine. In ruminants, a significant portion may be excreted in milk.

Half-Life: The half-life of febantel is short (approximately 1-2 hours in dogs), but the active metabolites have longer half-lives (fenbendazole: 10-15 hours in dogs).

Bioavailability: Oral bioavailability is low due to poor absorption and extensive first-pass metabolism; systemic bioavailability is estimated at <20% in most species.

Protein Binding: Febantel and its metabolites are moderately protein-bound (approximately 60-70%).

Available Formulations & Strengths

Oral Paste 10% (100 mg/g) (PO)

Oral Suspension 10% (100 mg/mL) (PO)

Oral Granules Various (PO)

Oral Tablet 150 mg, 300 mg, 500 mg (PO)

Combination Products Often combined with praziquantel and pyrantel (PO)

Contraindications & Clinical Warnings

Contraindications:

Hypersensitivity to febantel or other benzimidazoles
Do not use in animals with severe hepatic impairment
Do not use in pregnant animals unless benefit outweighs risk (especially during first trimester)
Do not use in lactating animals if milk is intended for human consumption (check withdrawal times)

Warnings & Clinical Precautions:

Use with caution in debilitated or severely parasitized animals; may cause a heavy parasite kill leading to toxemia.
In dogs, use with caution in breeds sensitive to benzimidazoles (e.g., Collies) due to potential MDR1 mutation.
In food animals, observe withdrawal times.
Do not exceed recommended dose.
Use in cats and kittens under 6 weeks of age with caution.
In horses, do not use in mares during early pregnancy unless directed by a veterinarian.

Adverse Effects & Reactions

Common:

Mild gastrointestinal upset (vomiting, diarrhea)
Salivation
Anorexia

Serious / Severe:

Bone marrow suppression (rare, with high doses)
Hepatotoxicity (rare)
Teratogenic effects (with high doses in early pregnancy)

Rare:

Allergic reactions
Ataxia
Convulsions (in overdose)

Key Drug Interactions

Interacting Drug / Class	Clinical Effect & Mechanism	Severity
Cimetidine	May increase plasma concentrations of febantel metabolites by inhibiting hepatic metabolism.	Moderate
Ivermectin	Potential for additive neurotoxicity in dogs with MDR1 mutation; use with caution.	High
Piperazine	Antagonistic effect; do not use concurrently.	Moderate
Other benzimidazoles (e.g., fenbendazole)	Additive effects; avoid concurrent use to prevent toxicity.	Moderate

Overdose & Toxicity Management

Signs of Toxicity:

Vomiting
Diarrhea
Ataxia
Depression
Tremors
Convulsions
Bone marrow suppression (with chronic overdose)

Emergency Treatment Protocol: There is no specific antidote. Treatment is symptomatic and supportive. Induce emesis if recent ingestion and animal is conscious. Administer activated charcoal to reduce absorption. Provide fluid therapy and supportive care. Monitor for neurological signs and bone marrow suppression. In severe cases, blood transfusions may be necessary.

Food Animal Withdrawal Times

🥩 Meat: 17 days🥛 Milk: 5 days

Withdrawal times vary by country and formulation. For cattle, meat withdrawal is typically 17 days and milk 5 days. For sheep, meat withdrawal is 14 days. Not approved for use in poultry or egg-laying birds in many countries.

Storage, Handling & Regulatory Information

Storage Temperature: Store at controlled room temperature 20-25°C (68-77°F), excursions permitted between 15-30°C (59-86°F).

Light Sensitivity: Light-sensitive — protect from direct exposure.

Handling & Special Conditions: Protect from light and moisture. Keep container tightly closed. Do not freeze.

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for use in dogs and horses in the US. Not approved for food animals in the US, but may be used extra-label.

Extra-Label (Off-Label) Use: In the US, febantel is approved for use in dogs and horses. Extra-label use in other species is permitted under AMDUCA with a valid veterinary-client-patient relationship. For food animals, extra-label use requires a withdrawal time established by the veterinarian, and must not result in violative residues.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Febantel is a prodrug of fenbendazole, providing a broad spectrum of anthelmintic activity. It is commonly used in combination with praziquantel and pyrantel for comprehensive deworming in dogs and cats. In horses, it is effective against small strongyles, including encysted larvae when used at higher doses for 5 days. In cattle and sheep, it is used for gastrointestinal nematodes and lungworms. Due to its poor absorption, it is generally well tolerated. However, resistance to benzimidazoles is a growing concern, so rotational deworming strategies are recommended. Always follow label directions and withdrawal times for food animals. In dogs, be cautious with breeds carrying the MDR1 mutation (e.g., Collies) as they may be more sensitive to neurological effects. For best results, fecal egg count reduction tests should be performed to monitor efficacy.

References & Literature

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