WHO Acute Hazard classification: Not listed.

Mechanism of action of Febantel

Febantel acts on the worms only after transformation to fenbendazole. The molecular mode of action of all benzimidazoles, including fenbendazole, consists in binding to tubulin, a structural protein of microtubules.

These microtubules are important organelles involved in the motility, the division and the secretion processes of cells in all living organisms.

In the worms the blocking of microtubules perturbs the uptake of glucose, which eventually empties the glycogen reserves. This blocks the whole energy management mechanism of the worms that are paralyzed and die or are expelled.

Since cell division is also disturbed, worm egg production and development is also blocked by benzimidazoles, i.e. most of them also have an ovicidal effect.

Acute Toxicity and Tolerance of Febantel

  • LD50 acute, rats, p.o. 1760 mg/kg
  • LD50 acute, dogs, p.o 10000 mg/kg
  • Livestock, pets and poultry usually tolerate febantel very well.
  • Safety margin in horses: ~40. Horses tolerate single oral doses of up to 240 mg/kg and daily doses of 24 to 48 mg/kg during 10 days without toxic xymptoms.
  • In dogs, daily oral doses of 5 to 10 mg/kg during 90 days caused testicular and prostatic hypostasia (underdevelopment).
  • In sheep, daily oral doses of 45 mg/kg oon day 17 of gestation caused malformations in kidneys and bones in >10% of the lambs born. It is thought that is was due to oxfendazole, one of the metabolites of febantel.

Toxic Symptoms caused by Febantel Poisoning

  • As a general rule, poisoning with febantel is quite unusual, due to its low toxicity, the high safety margins and the fact that most species tolerate febantel very well.
  • In dogs and cats heavy overdose (15x the therapeutic dose in adults, 10x in young animals) caused transient salivation (drooling), diarrhea, vomit and loss of appetite.
  • In young pigeons febantel at therapeutic doses can cause plumage damage.

Febantel Side Effects, Adverse Drug Reactions (ADRs) and Warnings

  • In puppies transient weight loss has been reported after treatment with febantel.
  • Both dogs and cats occasionally show vomit after treatment at the therapeutic dose.
  • Pregnant or lactating bitches should not be treated with febantel.
  • Febantel is very often administered together with pyrantel and/or praziquantel, mainly to dogs and cats. No incompatibilities or antagonic effects have been reported.
  • Never use tablets (or suspensions, pastes, etc.) for dogs in cats or tablets for large dogs in small dogs. It happens that some users want to save money buying large tablets for treating smaller dogs (or even cats!) twice or more times. The risk of overdosing is considerable, either due to erroneous calculations or to unskilled manipulation. In addition, dog medicines may sometimes contain ingredients that are toxic to cats.
  • Unless prescribed by a veterinary doctor, never use in dogs or cats products for livestock that are not explicitly approved for such use. There is a high risk of overdosing or of adverse drug reactions due to ingredients that are not tolerated by pets or are even toxic to them.

Antidote and Treatment of Febantel Intoxication

  • There is no specific antidote for febantel.
  • Treatment consists in supportive and symptomatic measures.
  • After oral intoxication gastric lavage is recommended, as well as administration of active charcoal.

Pharmacokinetics of Febantel

  • Following oral administration febantel is absorbed into the bloodstream by >40% and very quickly metabolized to fenbendazole and to fenbendazole sulfoxide (= oxfendazole), which both have a high anthelmintic efficacy.
  • Interestingly, the oxfendazole produced through metabolism is released back to the rumen, where the bacterial flora reduces it back to fenbendazole. This increases the bioavailability of fenbendazole in ruminants.
  • Excretion occurs mainly through feces. Excretion in goats is about twice as fast as in sheep. Excretion through milk is rather low. All metabolites in the milk fall below the detectable limit 60 hours after administration.
  • Influence of parasites. In ruminants, heavy infestations with gastrointestinal roundworms increase the pH in the abomasum, which reduces the solubility of febantel, its absorption into blood and its bioavailability. As a consequence, heavy infestations with gastrointestinal roundworms require a higher dose to achieve the same efficacy.

Environmental Toxicity of Febantel

  • Febantel is slightly toxic to fish.
  • Not being used in crop pesticides or in public hygiene, knowledge on its environmental fate and impact is very scarce.
  • Nevertheless, it can be assumed that correctly used in dogs, cats and livestock febantel is unlikely to be detrimental for the environment, including coprophagous insects.

Additional information

Click here for a list and overview of all safety summaries of antiparasitic active ingredients in this site.

  • Febantel belongs to the chemical class of the pro-benzimidazoles.
  • Febantel is not used in human medicines.
  • Febantel is not used in crop pesticides.
  • Febantel is not used in public or domestic hygiene as a biocide.
  • Click here for General safety of antiparasitics for domestic animals.
  • Click here for General safety of antiparasitics for humans.
  • Click here for General safety of antiparasitics for the environment.
  • Click here for technical and commercial information on febantel.


If you intend to use a veterinary drug containing this active ingredient you must carefully read and follow the safety instructions in the product label.  Always ask your veterinary doctor, or pharmacist, or contact the manufacturer. Be aware that the safety instructions for the same veterinary medicine may vary from country to country.

The information in this page must not be confused with the Materials and Safety Datasheets (MSDS) officially issued by manufacturers for active ingredients and many other chemicals. MSDSs target safety during manufacturing, transport, storage and handling of such materials. This safety summary is a complement to the information on product labels and MSDS.

The toxicity of an active ingredient must not be confused with the toxicity of finished products, in this case parasiticidal drugs or pesticides. Finished products contain one or more active ingredients, but also other ingredients that can be relevant from the safety point of view.

All information in this site is made available in good faith and following a reasonable effort to ensure its correctness and actuality. Nevertheless, no this regarding guarantee is given, and any liability on its accuracy, integrity, sufficiency, actuality and opportunity is denied. Liability is also denied for any possible damage or harm to persons, animals or any other goods that could follow the transmission or use of the information, data or recommendations in this site by any site visitor or third parties.