Flumethrin is an antiparasitic active ingredient used in veterinary medicine in livestock and pets against external parasites (lice, mites, fleas, flies, ticks, etc.). It is not used against agricultural or household pests. It belongs to the chemical class of the synthetic pyrethroids.

Common name: FLUMETHRIN

Type: pesticide
Chemical class: synthetic pyrethroid


Molecular structure of FLUMETHRIN





Type of action: Broad spectrum contact, non systemic ectoparasiticide: insecticide, acaricide, tickicide, louisicide
Main veterinary parasites controlled: flies, ticks, mites, lice, fleas, mosquitoes, etc.

Efficacy against a specific parasite depends on the delivery form and on the dose administered. 

Click here for general information on features and characteristics of PARASITICIDES.


Click here to view the article in this site with the most common dosing recommendations for flumethrin used in domestic animals.


Oral LD50, rat, acute*:  >2000 mg/kg
Dermal LD50, rat, acute*: >2000 mg/kg
* These values refer to the active ingredient. Toxicity has to be determined for each formulation as well. Formulations are usually significantly less toxic than the active ingredients.

Synthetic pyrethroids can be irritant for the skin and the eyes.

WARNING: Most synthetic pyrethroids can be toxic for cats.

MRL (maximum residue limit) set for animal tissues (either beef, mutton pork or chicken)*:

  • CODEX: Yes
  • EU: Yes
  • USA: No
  • AUS: Yes

* This information is an indicator of the acceptance of an active ingredient by the most influential regulatory bodies for use on livestock. MRL's for animal tissues may be set also for agricultural pesticides that are not approved for use on animals but are used on commodities fed to animals. A MRL may be also set in the form of an IMPORT TOLERANCE for active ingredients not approved in a particular country but approved for imported animal commodities.

Withholding periods for meat, milk, eggs, etc. depend on delivery form, dose and national regulations. Check the product label in your country.

Learn more about flumethrin safety.

General information on the safety of veterinary antiparasitics is available in specific articles in this site (click to visit):


Never use agricultural or hygiene products with this or any other active ingredient on livestock or pets, even if there are veterinary products with this same active ingredient approved for use on animals. The formulations for agricultural or hygiene use are different and may be toxic for livestock or pets.

It is obvious that veterinary products are not intended for and should never be used on humans!!!


Decade of introduction: 1970
Introduced by: BAYER
Some original brands: BAYTICOL
Patent: Expired (particular formulations may be still patent-protected)

Use in LIVESTOCK: Yes, abundant.
Use in HORSES: Yes, scarce
Use in
DOGS: Yes, scarce

Main delivery forms

Use in human medicine: No
Use in
public/domestic hygiene: No
Use in
agriculture: No
Generics available: 
Yes, a few


Visit also the section in this site about parasite resistance to antiparasitics and more specifically to flumethrin.


Flumethrin is a synthetic pyrethroid particularly effective against ticks and mites, but only mediocre against insects. It has been vastly used on livestock, but very seldom on pets.

Flumethrin is a mixture of various optic isomers, but all commercial products contain the same mixture, i.e. isomer content makes no difference in product quality or efficacy.

Although patent has expired long ago, there are rather few generic veterinary products available.

Efficacy of flumethrin

Flumethrin is an ectoparasiticide, i.e. active only against external parasites such asflies, ticks, mites, lice, fleas, mosquitoes, etc. However it is certainly more effective against livestock ticks and mites than other pyrethroid generalists such as cypermethrindeltamethrin and permethrin. It is one of the best active ingredients against both single-host ticks (e.g Boophilus spp) and multi-host ticks (e.g. Amblyomma, Rhipicephalus, Ixodes, Dermacentor, etc,). It is also excellent against several scab and mange mites (e.g. Psoroptes spp., Sarcoptes spp, etc.). However, it is only a mediocre insecticide less effective against flies, lice, fleas and mosquitoes than other synthetic pyrethroids.

As most synthetic pyrethroids, flumethrin is a mediocre larvicide, i.e. it is not a good option for the large-scale prevention of cutaneous myiases (e.g. screwworms, blowfly strike, etc.) with sprays, pour-ons, etc. 

Flumethrin, as well as many other synthetic pyrethroids has a significant repellent effect on certain ticks, which strongly depends on the delivery form and the dose administered.

However, resistance to flumethrin is widespread and can be very high in cattle ticks (Boophilus spp) and several insect species. As a consequence, products with flumethrin are already totally useless against cattle ticks in many places. The same applies to all other synthetic pyrethroids (e.g. cypermethrin, deltamethrin, permethrin, etc.). And this is true for whatever delivery form: dipping, spraying, pour-ons, etc.

Pharmacokinetics of flumethrin

Topically administered flumethrin remains mostly on the hair-coat of the treated animals and is very poorly absorbed through the skin. In contrast with natural pyrethrins and older synthetic pyrethroids flumethrin is quite resistant to UV-light, which allows a residual effect between 5 and 10 days for most sprays and dips.

Treated animals can ingest flumethrin through licking or grooming. A large amount of it is excreted unchanged through the feces. The absorbed flumethrin is quickly metabolized in the liver to inactive metabolites that are excreted through urine.  This is done by a specific enzyme called glucuronidase. However, cats lack this enzyme and cannot properly metabolize most synthetic pyrethroids. This is why most synthetic pyrethroids are toxic to cats.

As a general rule flumethrin products are approved for use on dairy animals in many countries.

Mechanism of action of flumethrin

Synthetic pyrethroids, including flumethrin, have a similar mode of action as organochlorines. They act on the membrane of nerve cells blocking the closure of the ion gates of the sodium channel during re-polarization. This strongly disrupts the transmission of nervous impulses. At low concentrations insects suffer from hyperactivity. At high concentrations they are paralyzed and die.

However it seems that flumethrin has a slightly different mechanism of action than other synthetic pyrethroids because there are cattle tick strains (Boophilus microplus) with high resistance to flumethrin but not to cypermethrin, and strains highly resistant to other synthetic pyrethroids but not against flumethrin.

Click here to view the list of all technical summaries of antiparasitic active ingredients in this site.