Albendazole

Benzimidazole anthelmintic Anthelmintic

Dosage & Administration Guidelines

Species Route Dose Frequency Duration & Clinical Notes
Dog PO 25 mg/kg q12h Duration: 3-5 days for giardiasis; single dose for roundworms/hookworms
Notes: Administer with food to enhance absorption. For tapeworms, may need higher dose or repeat.
Cat PO 25 mg/kg q12h Duration: 3-5 days for giardiasis; single dose for roundworms/hookworms
Notes: Use with caution in cats; safety not well established. Administer with food.
Horse PO 10 mg/kg Single dose Duration: One day
Notes: For tapeworms, use 10 mg/kg for 3-5 days or use praziquantel combination.
Cattle PO 10 mg/kg Single dose Duration: One day
Notes: For inhibited Ostertagia, use 10 mg/kg for 5 days or use a sustained-release bolus.
Sheep/Goats PO 10 mg/kg Single dose Duration: One day
Notes: For liver flukes, use 15 mg/kg for 5 days or use a flukicide combination.
Rabbit PO 20 mg/kg q24h Duration: 5 days
Notes: Often used off-label; monitor for GI upset.
Birds/Poultry PO 10-20 mg/kg q24h Duration: 3-5 days
Notes: May be administered in drinking water or feed; ensure adequate intake.
Reptiles PO 50 mg/kg Single dose, repeat in 14 days Duration: One day
Notes: Use with caution; safety in reptiles not well established.

Clinical Indications & Species Uses

General Indications
  • Broad-spectrum anthelmintic for gastrointestinal and systemic parasites
Dog (Canine)
  • Treatment of roundworms (Toxocara canis, Toxascaris leonina)
  • Hookworms (Ancylostoma caninum, Uncinaria stenocephala)
  • Whipworms (Trichuris vulpis)
  • Tapeworms (Taenia spp., Dipylidium caninum)
  • Giardiasis
Cat (Feline)
  • Treatment of roundworms (Toxocara cati)
  • Hookworms (Ancylostoma tubaeforme)
  • Tapeworms (Taenia taeniaeformis, Dipylidium caninum)
  • Giardiasis
Horse (Equine)
  • Treatment of large strongyles (Strongylus vulgaris, S. edentatus)
  • Small strongyles (Cyathostomins)
  • Ascarids (Parascaris equorum)
  • Pinworms (Oxyuris equi)
  • Tapeworms (Anoplocephala perfoliata)
Cattle (Bovine)
  • Treatment of gastrointestinal roundworms (Ostertagia, Haemonchus, Cooperia, Trichostrongylus)
  • Lungworms (Dictyocaulus viviparus)
  • Tapeworms (Moniezia spp.)
  • Liver flukes (Fasciola hepatica, adult stage)
  • Inhibited larval stages of Ostertagia
Small Ruminants (Sheep / Goat)
  • Treatment of gastrointestinal roundworms (Haemonchus, Teladorsagia, Trichostrongylus, Cooperia)
  • Lungworms (Dictyocaulus filaria)
  • Tapeworms (Moniezia spp.)
  • Liver flukes (Fasciola hepatica, adult stage)
Rabbit & Small Mammals
  • Treatment of intestinal parasites (Passalurus ambiguus, Obeliscoides cuniculi)
  • Encephalitozoon cuniculi (off-label)
Avian & Poultry
  • Treatment of roundworms (Ascaridia spp.)
  • Capillaria spp.
  • Tapeworms (Raillietina spp.)
Exotic & Other Species
  • Treatment of nematodes and cestodes in reptiles (e.g., roundworms, tapeworms)
  • Treatment of parasites in small mammals (e.g., guinea pigs, hamsters)

Pharmacology & Mechanism of Action

Drug Class: Benzimidazole anthelmintic | Pharmacological Group: Anthelmintic

Mechanism of Action: Albendazole binds to the colchicine-sensitive site of tubulin, inhibiting its polymerization into microtubules. This disrupts microtubule-dependent cellular functions, including glucose uptake and intracellular transport, leading to depletion of glycogen stores and ATP production in parasitic cells. The parasite becomes paralyzed and dies due to energy depletion. It is active against larval and adult stages of nematodes, cestodes, and some trematodes.

Pharmacodynamics: Albendazole has a broad spectrum of anthelmintic activity. It is effective against gastrointestinal roundworms, lungworms, tapeworms, and liver flukes. Its ovicidal and larvicidal effects are particularly useful in treating mixed infections. The drug is also active against Giardia and some protozoa. In ruminants, it reduces fecal egg counts and improves weight gain. The onset of action is slow but sustained, with effects lasting several days.

⚡ Pharmacokinetics Summary

Absorption: Albendazole is poorly absorbed from the gastrointestinal tract. Oral bioavailability is low (about 20-30%) in most species, but absorption is enhanced when administered with a fatty meal. In ruminants, the rumen microflora may metabolize albendazole to some extent before absorption.
Distribution: After absorption, albendazole is widely distributed in tissues, with high concentrations in the liver, kidney, and bile. It crosses the blood-brain barrier to a limited extent. It is also distributed into milk and crosses the placenta.
Metabolism: Albendazole undergoes extensive first-pass metabolism in the liver. It is rapidly oxidized to albendazole sulfoxide (the active metabolite) and then to albendazole sulfone (inactive). The sulfoxide is responsible for most of the anthelmintic activity.
Excretion: The metabolites are excreted primarily in bile and feces. A small amount is excreted in urine. In lactating animals, a small percentage is excreted in milk.
Half-Life: The half-life of albendazole sulfoxide is approximately 8-12 hours in cattle, 6-10 hours in sheep, and 4-6 hours in dogs and cats.
Bioavailability: Oral bioavailability is low (20-30%) in monogastric animals, but higher in ruminants due to prolonged rumen retention and enterohepatic recycling.
Protein Binding: Albendazole sulfoxide is approximately 70% protein-bound in plasma.

Available Formulations & Strengths

Oral Tablet 200 mg, 400 mg, 600 mg (PO)
Oral Suspension 100 mg/mL, 200 mg/mL (PO)
Paste 10%, 20% (PO)
Granules/Powder Various (PO)
Injectable Solution (not common) Not commonly available (SC/IM)

Contraindications & Clinical Warnings

Contraindications:
  • Hypersensitivity to albendazole or other benzimidazoles
  • Pregnancy (especially first trimester) in dogs, cats, and livestock due to teratogenic effects
  • Lactating animals (unless specifically indicated and withdrawal times observed)
  • Severe hepatic or renal impairment
  • Do not use in animals with known bone marrow suppression
Warnings & Clinical Precautions:
  • Use with caution in debilitated animals or those with severe parasitic infections (risk of endotoxic shock due to dead parasite release)
  • In ruminants, use with caution in animals with liver fluke infections as it may exacerbate liver damage
  • Do not crush tablets; may be irritating to eyes and mucous membranes
  • In horses, avoid use in stallions at breeding time due to potential effects on spermatogenesis
  • In cats, use with caution as safety has not been fully established; monitor for signs of toxicity
  • In food animals, observe withdrawal times; extra-label use requires veterinary oversight
  • May cause bone marrow suppression with prolonged use; monitor blood counts in long-term therapy

Adverse Effects & Reactions

Common:

  • Mild gastrointestinal upset (vomiting, diarrhea, anorexia)
  • Salivation
  • Lethargy

Serious / Severe:

  • Bone marrow suppression (neutropenia, thrombocytopenia, anemia)
  • Hepatotoxicity
  • Teratogenic effects (if used during pregnancy)
  • Neurological signs (ataxia, seizures) in overdose

Rare:

  • Allergic reactions (urticaria, angioedema)
  • Alopecia
  • Fever

Key Drug Interactions

Interacting Drug / Class Clinical Effect & Mechanism Severity
Cimetidine May increase plasma concentrations of albendazole sulfoxide by inhibiting its metabolism, potentially increasing efficacy and toxicity. Moderate
Dexamethasone May increase plasma concentrations of albendazole sulfoxide, possibly enhancing efficacy but also toxicity. Moderate
Praziquantel Additive or synergistic anthelmintic effect; commonly used in combination for tapeworms. Mild
Ivermectin Additive anthelmintic effect; may increase risk of neurological toxicity in some species (e.g., collies with MDR1 mutation). Moderate
Nitroscanate Potential for increased hepatotoxicity; avoid concurrent use. High

Overdose & Toxicity Management

Signs of Toxicity:

  • Vomiting
  • Diarrhea
  • Ataxia
  • Depression
  • Tremors
  • Seizures
  • Bone marrow suppression (with chronic overdose)
  • Hepatotoxicity

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 intravenous fluids, electrolyte replacement, and supportive care. Monitor liver enzymes and blood cell counts. In severe cases, blood transfusions may be necessary.

Food Animal Withdrawal Times

🥩 Meat: 27 days🥛 Milk: 3 days

Withdrawal times vary by country and formulation. In the US, for cattle, meat withdrawal is 27 days and milk withdrawal is 3 days. For sheep, meat withdrawal is 7 days (but not approved for sheep in the US). In other countries, check local regulations. For poultry, not approved in laying hens; withdrawal times may be longer.

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).

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

Dispensing Status: Prescription Required (Rx Only)

Approval Status: Approved for use in cattle and sheep (as Valbazen) in the US. Not approved for dogs, cats, horses, or other species, but commonly used extra-label.

Extra-Label (Off-Label) Use: In the US, albendazole is approved for cattle and sheep (but not sheep in the US). Use in other species is extra-label and requires a veterinary prescription under AMDUCA. Extra-label use in food animals requires a valid veterinary-client-patient relationship and extended withdrawal times.

Clinical Pearls & Practice Notes

💡 Clinical Insights: Albendazole is a broad-spectrum anthelmintic effective against many internal parasites. It is particularly useful for treating tapeworms and liver flukes in ruminants. In small animals, it is often used for giardiasis and resistant parasites. Due to potential bone marrow toxicity, it should not be used for prolonged periods without monitoring. In food animals, strict adherence to withdrawal times is essential. For horses, it is effective against tapeworms but may require higher doses or repeated administration. Always confirm the diagnosis and consider fecal egg count reduction tests to monitor efficacy. In cases of parasite resistance, rotation with other anthelmintic classes is recommended.

References & Literature

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