KNOW ABOUT ONE DRUG EVERY DAY FENBENDAZOLE

KNOW ABOUT ONE DRUG EVERY DAY

FENBENDAZOLE

Benzimidazole anthelmintic agent.

Type                                       Benzimidazole anthelmintic.

Pharmacology & General Information

Pharmacology

• Binds to tubulin, a protein required for functions including nutrient uptake, thus disrupting parasite energy metabolism.

Therapeutic Information

Uses/Indications

Activity

• Active against adult roundworms and larvae, also kills roundworm eggs (ovicidal).
• Active against tapeworms.

Appropriate Use

• Dog: used in pregnant and lactating bitches to reduce  roundworms in their puppies.
• Dog, cat: against lungworm infections.; against some tapeworms.
• Ruminants: against roundworms, tapeworms.
• Generally considered safe for use in pregnant animals.
• Has been used in the treatment of cats, sheep, goats, llamas and pet birds.

Indications:

• UK: "Gastro-intestinal roundworms in horses, ruminants, pigs, dogs, cats, and pigeons; Type II ostertagiosis; transplacental roundworm transmission in dogs; lungworms in ruminants, pigs, dogs, and cats; Trichostrongylus tenuis in grouse; tapeworms in ruminants; Taenia in dogs and cats; Giardia in dogs."
• USA:
• Dogs: labelled for removal of ascarids (Toxocara canis, Toxocara leonina), hookworms (Ancyclostoma caninum, Uncinaria stenocephala), whipworms (Trichuris vulpis), tapeworms (Taenia pisiformis). Also used clinically for treatment of Capillaria aerophila, Filaroides hirthi and Paragonimus kellicotti.
• Cattle: labelled for removal of adult Haemonchus contortus, Ostertagia ostertagi, Trichostrongylus axei, Bunostomum phlebotomum, Nematodirus helvetianus, Cooperia spp., Trichostrongylus colubriformis, Oesophagostomum radiatum, Dictyocaulus vivaparus. Also effective against the immature stages of most of these parasites, and has good activity (although not labelled for) Monezia spp. and arrested 4th stage Ostertagia ostertagi.
• Horses: labelled for removal of large strongyles (Strongylus edentatus, Strongylus equinus, Strongylus vulgaris, small strongyles (Cyathostomum spp., Cylicocylus spp., Cylicostephanus spp., Triodontaphorus spp.), pinworms (Oxyuris equi).
• Pigs: labelled for removal of large roundworms Ascaris suum, lungworms Matastrongylus apri, nodular worms Oesophagostomum dentatum, Oesophagostomum quadrispinulatum, small stomach worms Hyostrongylus rubidus, whipworms Trichuris suis and kidney worms Stephanuris dentatus (mature and immature).

Limitations

• Not effective against flukes (trematodes).
• In dogs, cats, singled dose treatment, even at a high dose rate, is not effective; a minimum of three days of treatment is required.
• Not effective against Dipilidium caninum.

Pharmacokinetics and Drug Interactions

Absorption /Bioavailability

• Oral administration results in only marginal absorption from the gut:
• Peak blood levels in calves 0.11 µg/ml, in horses 0.07 µg/ml.

Distribution

Plasma Protein binding / Storage

• In ruminants and horses the rumen or large intestine respectively acts as a drug reservoir, thereby maintaining therapeutic concentrations for longer periods (compared with a single does in dogs, cats or pigs).

Elimination Route

• Absorbed fenbendazole is metabolised to active oxfendazole sulfoxide and to the sulfone.
• Cattle, sheep, pigs: excreted mainly (44-50%) in the faeces (unchanged), with only very small amounts (less than 1%) eliminated in urine.

Drug Interactions

• Use concurrently with brosalan flukicides (dibromsalan, tribromsalan) has resulted in abortions in cattle and been fatal in sheep.

Administration

Formulations available

• Various preparations are available for oral administration.

Doses / Administration Routes / Frequencies

General comments:

• Dogs, cats: single dose not effective; three days of treatment are required.

Dogs:

• Generally 50 mg/kg orally for three consecutive days, e.g. for susceptible ascarids, hookworms, whipworms and tapeworms (active against Taenia spp. tapeworms but not against Dipylidium caninum).
• For Giardia infection, 50 mg/kg orally daily for three days, or 25 mg/kg orally every 12 hours for 3-7 days.
• For Capillaria aerophila, 25-50 mg/kg every 12 hours for 10-14 days, or 50 mg/kg orally once daily for 10-14 days.
• For roundworms, tapeworms and Giardia. Orally, 50 mg/kg daily for three days (treatment in adults); 50 mg/kg daily for three days in pups under six months old, for prophylaxis; 100 mg/kg as a single dose for treatment in adults.
• For transplacental transmission, 25 mg/kg daily from day 40 of pregnancy through to two days postpartum.
• For lungworms, 50 mg/kg daily for seven days.

Elephants:

Elephas maximus - Asian Elephant:

For gastro-intestinal nematode infection:

• 12 g dissolved in 200 ml of water as a single dose.
• 5 mg/kg orally as a single dose.

Elephants:
For strongylosis:
a) 5 mg/kg po (Raman, et.al., 2000).
b) 2.5 mg/kg orally as a single dose (Chandrasekharan,2002); (Chandrasekharan et.al.,1995).
c) 2.0 –2.5 mg/kg orally as a single dose mixed with jaggery or rice (Chandrasekharan, 1992).
d) 5 mg/kg po in feed as a single dose (Strao et.al., 1992).
e) Chronic murshidiasis in an Asian elephant was resolved with 50 g fenbendazole repeated at 30 days (Tripathy et.al. 1991).
f) 5 mg/kg po as a single dose (Roy and Mazumdar, 1988).
Lagomorphs - Oryctolagus cuniculus domesticus - Domestic rabbit:

• 5 mg/kg orally.
• 10 mg/kg orally, repeat after 14 days.
• 20 mg/kg orally every 24 hours for seven days before and for two days after mixing rabbits. As a preventative against. Encephalitozoonosis in Lagomorphs. (B548.w8)
• 20 mg/kg orally every 24 hours for 28 days in the treatment of Encephalitozoonosis in Lagomorphs.
• 50 ppm in feed for two to six weeks.
• 10 - 20 mg/kg orally, repeated after 14 days.
• 50 mg/kg feed for a period of five days to six weeks. For the treatment of Encephalitozoonosis in Lagomorphs.
• 20 mg/kg orally. In the treatment of Encephalitozoonosis in Lagomorphs.

Ferrets - Mustela putorius fero - Ferret:

• 20 mg/kg orally, daily for five days. For the treatment of nematodes.
• 50 mg/kg once daily orally for three days.

Pigeon

• 20mg/kg, orally.

Exotic birds

• Against nematodes 50-100 mg/kg, orally, single dose, repeat after 10 days.
• Against microfilaria and trematodes 33mg/kg orally, repeat daily for three days.
• Against capillaria 20mg/kg, repeat daily for five days.

Reptiles

• 50-100mg/kg bodyweight orally every 5-7 days for roundworms.

Amphibians

• Against roundworms. 50-100mg/kg orally, every 14 days.

Toxic Information

Toxic effects of Pharmaceutical Products

Contraindications / Precautions

• Contra-indicated for administration within 14 days of treatment for liver fluke.
• Administration of ruminal bolus is contra-indicated in cattle which are not ruminating or are less than 100 kg and three month old. 
• Ruminal bolus is contra-indicated for administration concurrent with other ruminal boluses.
• Contra-indicated for treatment of grouse later than March.
• Not for administration within 14 days of the second dose of vaccine in cattle being vaccinated against lungworm.
• Not recommended for treatment of pigeons during the main moult.
• Not recommended for treatment of pigeons when rearing young.
• Toxicity has been reported or suspected in several bird species.

Adverse Effects / Side Effects / Warnings

• Rarely causes any adverse effects.
• Hypersensitivity reactions may occur secondary to release of antigens by dying parasites; this is more likely to occur at high dose rates.
• Dogs, cats: infrequently vomiting occurs.

Overdose / Acute Toxicity

• Generally well tolerated at doses as high as 100 times recommended.

Detailed Toxicological Information

Acute Toxicity

• Laboratory animals oral LD₅₀ greater than 10 g/kg.

Toxicity has been reported or suspected in several bird species.