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Type: pesticide
Chemical class: synthetic pyrethroid


Molecular structure of DELTAMETHRIN







Type of action: Broad spectrum contact, non systemic ectoparasiticide: insecticide, acaricide, tickicide, louisicide, larvicide
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. National regulatory authorities determine whether a product is approved for a given indication, i.e. use on a particular host at a specific dose and against a specific parasite. Check the labels of the products available in your country.

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


Oral LD50, rat, acute*:  135-5000 mg/kg, depending on the vehicle
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.

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: Yes
  • 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 deltamethrin 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
Some original brands: BUTOX
Patent: Expired (particular formulations may be still patent-protected)

Use on LIVESTOCK: Yes, abundant
Use on HORSES: Yes, moderate
Use on
DOGS and CATS: Yes, scarce
Main delivery forms

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


On livestock & horses: Yes, as for all synthetic pyrethroids: very frequent worldwide in such species as cattle ticks (Boophilus spp), horn flies (Haematobia irritans), sheep lice (Damalinia ovis), poultry mites (Dermanyssus gallinae), houseflies (Musca domestica), mosquitoes.
On pets: Yes, quite frequent worldwide in dog and cat fleas (Ctenocephalides spp).

Learn more about parasite resistance and how it develops.


Deltamethrin is a synthetic pyrethroid with a spectrum of activity similar to cypermethrin. It has been vastly used on livestock, but seldom on pets.

In contrast with other synthetic pyrethroids, deltamethrin is not a mixture of various optic isomers, but is to 100% a cis isomer.

Although patent has expired long ago, there are only a few generic veterinary products available, probably because cypermethrin lost its patent protection earlier than deltamethrin and because cypermethrin is good enough.

Efficacy of deltamethrin

Deltamethrin is an ectoparasiticide, i.e. active only against external parasites such as flies, ticks, mites, lice, fleas, mosquitoes, etc. It can be considered as a broad-spectrum generalist, i.e. quite good against almost all insects, ticks and mites, but not outstanding against a particular parasite. It is certainly less efficient against multi-host ticks (e.g. Amblyomma, Rhipicephalus, Ixodes, Dermacentor, etc,) than several other tickicides (e.g. amitraz, chlorfenvinphos, coumaphos, flumethrin, etc.).

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

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

However, resistance to deltamethrin is widespread and can be very highin cattle ticks (Boophilus spp), horn flies (Haematobia irritans), red poultry mites (Dermanyssus gallinae), sheep lice (Damalinia ovis), houseflies (Musca domestica), dog and cat fleas (Ctenocephalides spp) and mosquitoes. As a consequence, products with deltamethrin are already totally useless against these important parasites in many places. The same applies to all other synthetic pyrethroids (e.g. cypermethrin, flumethrin, permethrin, etc.). And this is true for whatever delivery form: dipping, spraying, pour-ons, ear-tags, shampoos, soaps, etc.

Notice. As a general rule this site does not provide information about off-label uses of antiparasitic active ingredients. In most countries veterinary doctors can prescribe a veterinary medicine (also a parasiticide) for indications that are not included in its label. This is often the case for minor species  (e.g. rabbits, guinea pigs, exotic mammals and birds, reptiles, etc.) and orphan diseases  (also parasites) that are not investigated by pharmaceutical companies for whatever reasons.

Pharmacokinetics of deltamethrin

Topically administered deltamethrin 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 deltamethrin 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 deltamethrin through licking or grooming. A large amount of it is excreted unchanged through the feces. The absorbed deltamethrin is quickly metabolized in the liver to non-toxic metabolites that are excreted through urine. This is done by a specific enzyme called glucuronidase. However, cats lack this enzyme and cannot metabolize most synthetic pyrethroids. This is why most synthetic pyrethroids are toxic to cats.

As a general rule deltamethrin products are approved for use on dairy animals and on laying hens in many countries.

Mechanism of action of deltamethrin

Synthetic pyrethroids, including deltamethrin, 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.

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