Albendazole

Albendazole is a benzimidazole anthelmintic used mainly in livestock against susceptible gastrointestinal nematodes, lungworms, cestodes and adult liver flukes. Its useful spectrum varies with the parasite, host species and regimen; the presence of broad anthelmintic activity does not mean that every life stage is equally susceptible.

Historical small-animal uses include respiratory helminths and Giardia, but bone-marrow toxicity makes safer alternatives preferable for many canine and feline applications. Its effects on rapidly dividing cells also explain why reproductive status and species-specific restrictions matter.

Group

Benzimidazole anthelmintic; antiprotozoal

Mechanism of Action

Albendazole binds parasite beta-tubulin and inhibits assembly of microtubules. Microtubules are needed for intracellular transport, nutrient uptake, maintenance of cell structure and cell division. Disrupting these functions reduces glucose utilization and energy availability, progressively impairing parasite survival rather than producing an immediate nonspecific expulsion effect.

After absorption, albendazole is converted to metabolites, including albendazole sulfoxide, that contribute to systemic antiparasitic activity. Exposure and persistence differ among host species and help determine activity at intestinal and extraintestinal sites.

Preferential effects on parasite tubulin provide a therapeutic margin, but host cells are not completely protected. Injury to proliferating marrow and intestinal cells can occur, particularly with unsuitable exposure, and interference with embryonic development underlies important pregnancy restrictions. Anthelmintic resistance can reduce response even when the drug’s nominal spectrum includes the organism.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Intestinal helminths	25–50 mg/kg	PO	Every 12 h	Up to 3 days; Do not use in: First 45 days of pregnancy, Pre-existing marrow suppression; Historical regimen; safer alternatives are preferred because serious marrow toxicity can occur. Monitor CBC.
Respiratory parasites	50 mg/kg	PO	Every 24 h	Up to 14 days; Do not use in: First 45 days of pregnancy, Pre-existing marrow suppression; Historical 10-14 day course with substantial marrow-toxicity concern; other treatments are preferred. Monitor CBC.
Giardiasis	25 mg/kg	PO	Every 12 h	Up to 2 days; Do not use in: First 45 days of pregnancy, Pre-existing marrow suppression; Historical regimen; safer alternatives are preferred because serious marrow toxicity can occur. Monitor CBC.
Paragonimus kellicotti infection	25 mg/kg	PO	Every 12 h	Up to 14 days; Do not use in: First 45 days of pregnancy, Pre-existing marrow suppression; Parasite-specific regimen; marrow suppression remains a concern. Monitor CBC and consider safer alternatives.
Filaroides hirthi infection	25 mg/kg	PO	Every 12 h	Up to 5 days; Do not use in: First 45 days of pregnancy, Pre-existing marrow suppression; A repeat course after two weeks has been described. Monitor respiratory response and CBC.
Filaroides hirthi infection	50 mg/kg	PO	Every 12 h	Up to 5 days; Do not use in: First 45 days of pregnancy, Pre-existing marrow suppression; Separate higher-dose regimen with a repeat after 21 days; respiratory signs can worsen after parasite death. Monitor CBC.
Oslerus osleri infection	25 mg/kg	PO	Every 12 h	Up to 5 days; Do not use in: First 45 days of pregnancy, Pre-existing marrow suppression; Repeat after two weeks has been described. Monitor CBC and clinical response.
Capillaria plica infection	50 mg/kg	PO	Every 12 h	Up to 14 days; Do not use in: First 45 days of pregnancy, Pre-existing marrow suppression; Reported course 10-14 days; anorexia and marrow toxicity are concerns. Monitor CBC.
Leishmaniasis	10 mg/kg	PO	Every 24 h	Up to 30 days; Historical regimen; retain serious marrow-toxicity precautions and assess response.
Leishmaniasis	5 mg/kg	PO	Every 6 h	Up to 60 days; Separate prolonged historical course, not the same schedule as the once-daily alternative. Monitor CBC and liver function.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Intestinal helminths	25–50 mg/kg	PO	Every 12 h	Up to 3 days; Do not use in: First 45 days of pregnancy, Pre-existing marrow suppression; Historical regimen; safer alternatives are preferred because serious marrow toxicity can occur. Monitor CBC.
Respiratory parasites	50 mg/kg	PO	Every 24 h	Up to 14 days; Do not use in: First 45 days of pregnancy, Pre-existing marrow suppression; Historical 10-14 day course with substantial marrow-toxicity concern; other treatments are preferred. Monitor CBC.
Giardiasis	25 mg/kg	PO	Every 12 h	Up to 2 days; Do not use in: First 45 days of pregnancy, Pre-existing marrow suppression; Historical regimen; safer alternatives are preferred because serious marrow toxicity can occur. Monitor CBC.
Paragonimus kellicotti infection	25 mg/kg	PO	Every 12 h	Up to 14 days; Do not use in: First 45 days of pregnancy, Pre-existing marrow suppression; Parasite-specific regimen; marrow suppression remains a concern. Monitor CBC and consider safer alternatives.
Liver flukes	50 mg/kg	PO	Every 24 h	Historical Platynosum/Opisthorchiidae regimen continued until ova are no longer detected. Marrow toxicity is a substantial concern; duration is response-dependent.

Birds

Use / stage	Dose	Route	Schedule	Instructions
Helminth infection	50–100 mg/kg	PO	Every 24 h	Up to 9 days; Reported 2-9 day range spans different avian species; species-specific tolerance is not established by this generic bird entry.

Cattle

Use / stage	Dose	Route	Schedule	Instructions
Susceptible helminths and adult liver flukes	10 mg/kg	PO	Once	Do not use in: First 45 days of pregnancy, First 45 days after bull removal, Female dairy cattle of breeding age; For Valbazen 11.36%: meat withdrawal 27 days; not for female dairy cattle of breeding age.
Adult liver flukes	15 mg/kg	PO		Separate adult-fluke regimen; do not infer activity against immature flukes. Apply reproductive and product-specific food-animal restrictions.
Susceptible helminths	7.5 mg/kg	PO		Separate lower alternative for susceptible parasites; not the adult-fluke dose.

Sheep

Use / stage	Dose	Route	Schedule	Instructions
Susceptible helminths and adult liver flukes	7.5 mg/kg	PO	Once	Do not use in: First 30 days of pregnancy, First 30 days after ram removal; For Valbazen 11.36%: meat withdrawal 7 days.
Adult liver flukes	15 mg/kg	PO		Separate adult-fluke regimen; do not infer activity against immature flukes. Apply reproductive and product-specific food-animal restrictions.

Goats

Use / stage	Dose	Route	Schedule	Instructions
Adult liver flukes	10 mg/kg	PO	Once	Do not use in: Lactating does, First 30 days of pregnancy, First 30 days after buck removal; Nonlactating goats. For Valbazen 11.36%: meat withdrawal 7 days; this regimen is specific to adult liver flukes.
Adult liver flukes	15 mg/kg	PO		Separate adult-fluke regimen; do not infer activity against immature flukes. Apply reproductive and product-specific food-animal restrictions.
Susceptible helminths	7.5 mg/kg	PO		Separate single-dose oral-suspension regimen; apply the selected product restrictions.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Dictyocaulus arnfieldi infection	25 mg/kg	PO	Every 12 h	Up to 5 days; Historical equine regimen; assess alternative anthelmintics and susceptibility.
Strongylus vulgaris infection	50 mg/kg	PO	Every 12 h	Up to 2 days; Historical high-dose regimen; assess alternative anthelmintics and susceptibility.

Pigs

Use / stage	Dose	Route	Schedule	Instructions
Susceptible helminths	5–10 mg/kg	PO		Do not use in: Early pregnancy; Reported oral dose; the repeat interval is not specified. Establish an appropriate food withdrawal interval.

Rabbits

Use / stage	Dose	Route	Schedule	Instructions
Encephalitozoon cuniculi infection	20 mg/kg	PO	Every 24 h	Up to 10 days; Do not use in: Pregnancy, Pre-existing marrow suppression; Reported alternative; fenbendazole is generally preferred. Monitor CBC because benzimidazole-associated marrow injury can occur.
Encephalitozoon-associated phacoclastic uveitis — Initial	30 mg/kg	PO	Every 24 h	Up to 30 days; Do not use in: Pregnancy, Pre-existing marrow suppression; Reported initial course followed by the lower maintenance dose; assess ocular disease separately and monitor CBC.
Encephalitozoon-associated phacoclastic uveitis — Maintenance	15 mg/kg	PO	Every 24 h	Up to 30 days; Do not use in: Pregnancy, Pre-existing marrow suppression; Follows the initial course; monitor CBC and clinical response.

Chinchillas

Use / stage	Dose	Route	Schedule	Instructions
Giardiasis	50–100 mg/kg	PO	Every 24 h	Up to 3 days; Do not use in: Pregnancy, Pre-existing marrow suppression; Reported chinchilla regimen; do not extrapolate this high exposure to other small mammals.

Ratites

Use / stage	Dose	Route	Schedule	Instructions
Flagellate and tapeworm infection	Reference only	PO		Suspension regimen described as 1 mL/22 kg twice daily for three days, repeated after two weeks. The dose entry does not independently state the suspension concentration; retain the volume wording without assuming it applies to every product.

Indications

Treatment of susceptible gastrointestinal nematodes, lungworms and tapeworms in livestock.
Treatment of susceptible adult liver-fluke infections in cattle, sheep and selected nonlactating goats.
Historical treatment of selected intestinal and respiratory helminths in dogs, cats, horses and birds, including described lungworm infections.
Historical treatment of giardiasis in dogs and cats.

Contraindications

Early pregnancy: avoid during the first 45 days in cattle; Valbazen excludes the first 30 days in ewes and does.
Dogs and cats can develop severe marrow suppression, including idiosyncratic reactions.
Prolonged or high-dose courses increase toxicity risk.
Valbazen must not be used in female dairy cattle of breeding age or in lactating does; product-specific food restrictions remain essential.
Do not assume that a livestock regimen or safety margin applies to birds.
Pigeons and doves can be particularly susceptible to intestinal crypt injury and marrow suppression.
Severe diarrhea, neutropenia and fatal sepsis have been reported in alpaca crias given high repeated doses.
Rabbits can develop severe marrow aplasia with benzimidazole exposure; prefer better-supported alternatives when treating encephalitozoonosis and monitor CBC during prolonged treatment.

Interactions

Cimetidine can increase albendazole-metabolite concentrations in bile or cyst fluid; clinical veterinary significance is uncertain.
Dexamethasone and praziquantel may increase exposure to the active albendazole sulfoxide metabolite.

Adverse effects

Anorexia and lethargy.
Leukopenia, thrombocytopenia, pancytopenia or marrow hypoplasia in dogs and cats.
Gastrointestinal epithelial injury with high exposure.
Embryotoxicity or teratogenicity during susceptible early gestation.

Toxicity

Bone-marrow toxicity may be dose-related or idiosyncratic, particularly in cats. Stop treatment if suspected and monitor serial CBCs; cytopenias require supportive management. Early gestational exposure can harm the embryo or fetus.

Preparations

Preparation	Form	Strength	Route
Valbazen 11.36% Oral Suspension Shake well. Cattle meat withdrawal 27 days; sheep/goat meat withdrawal 7 days. Not for female dairy cattle of breeding age or lactating does. Store at room temperature protected from freezing.	Oral Liquid	113.6 mg / mL	PO
Zentel 400 mg Chewable Tablets	Tablet	400 mg / tablet	PO
Zentel Oral Suspension 400 mg/10 mL Shake well; concentration is 40 mg/mL. Store at room temperature protected from freezing.	Oral Liquid	400 mg / 10 mL	PO
Zentel 200 mg Tablets	Tablet	200 mg / tablet	PO
Zentel Suspension 100 mg/5 mL	Oral Liquid	100 mg / 5 mL	PO

Monitoring and Administration

Historical small-animal regimens exist, but bone-marrow injury makes other drugs preferable for routine canine or feline giardiasis. Extended courses and avian use require particular caution.

Assess parasite-specific efficacy, including fecal testing when appropriate. During extended courses or when adverse signs develop, monitor CBC and hepatic enzymes; discontinue and investigate unexplained cytopenias or jaundice.

Adult liver-fluke activity does not establish efficacy against immature flukes. Select treatment according to parasite stage, host and susceptibility.

Shake suspensions before measuring. For treatment exceeding one month, the source describes CBC and liver-enzyme monitoring every 4–6 weeks. Detect and investigate cytopenias or hepatic abnormalities promptly.