EFFICACY AGAINST PARASITES
Efficacy against a specific parasite depends on the delivery form and on the dose administered.
Click here to view the article in this site with the most common dosing recommendations for amitraz used in domestic animals.
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Oral LD50, rat, acute*: 800 mg/kg
Dermal LD50, rat, acute*: >1600 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: amitraz is toxic for cats and horses!
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 amitraz safety.
General safety information for antiparasitics is available in specific articles in this site (click to visit):
- General safety of antiparasitics for domestic animals
- General safety of antiparasitics for humans
- General safety of antiparasitics for the environment
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!!!
MARKETING & USAGE
Decade of introduction: 1970
Introduced by: BOOTS & Co -> CAMCO (...→ HOECHST → INTERVET → MERCK ANIMAL HEALTH)
Some original brands: TAKTIC, TRIATIX, TRIATOX
Patent: Expired (particular formulations may be still patent-protected)
Use in LIVESTOCK: Yes, very abundant
Use in HORSES: NO. Amitraz is toxic to horses
Use in DOGS and CATS: Yes, moderate
Main delivery forms:
Use in human medicine: No
Use in public/domestic hygiene: No
Use in agriculture: Yes
Generics available: Yes, a lot
In livestock: Yes: common in cattle ticks (Boophilus spp), and increasing.
In pets: No
Amitraz is a veteran ectoparasiticide, but still an excellent tickicide extensively used in livestock, mainly in cattle. It is effective against ticks that are already resistant to synthetic pyrethroids and/or organophosphates. Amitraz has a detachment effect: if they are not directly killed, ticks leave the host before completing or even initiating their blood meal. Amitraz also has a repellent effect that keeps many ticks away from treated animals. This repellent effect can have a drawback: amitraz treated livestock may be clean of ticks, because larvae in the pastures are repelled. But the pastures can remain highly infested. As soon as the repellent effect declines or another not repelling product is used, livestock on such pastures may become highly infected very quickly. Amitraz is also effective against scab and mange mites (Psoroptes spp, Sarcoptes spp, etc.) and against certain lice species.
BUT it does not control biting flies and other bloodsucking insects. AND it is unstable in cattle dips that have to be stabilized with lime or fully replenished. AND it is toxic for horses and cats.
Shortly after the introduction of amitraz in the 1970's synthetic pyrethroids came to market that where not only good tickicides, but also excellent insecticides, safer for livestock, not toxic for horses and stable in cattle dips. Synthetic pyrethroids vastly replaced amitraz in the 1980's and 1990's. BUT, cattle ticks (Boophilus spp) developed quickly resistance to synthetic pyrethroids. Nowadays this resistance is so strong and widespread, that amitraz has experienced a strong comeback in all tropical and subtropical regions where Boophilus ticks are a problem and cattle dips are still popular. In the 1990's there were only a few commercial brands with amitraz available for cattle (basically the original ones: TAKTIC, TRIATIX, etc.). Today there are dozens of brands in the market, also from multinational companies. Usage of amitraz has rocketed, probably because it is the only reliable tickicide left for dipping and spraying cattle after the failure of synthetic pyrethroids and the general rejection of organophosphates: other alternative tickicides such as macrocyclic lactones and fluazuron are not available for cattle dipping or spraying.
Amitraz has also experienced a certain revival for use in dogs. The reason is that a number of insecticides (e.g. imidacloprid, spinetoram) used in spot-ons are highly effective against fleas, but only poorly or not at all effective against ticks. They are sometimes mixed with amitraz to improve this efficacy against ticks.
Pharmacokinetics of amitraz
Dermal absorption of topically administered amitraz is quite low, less than 10% in dogs and pigs. However treated animals may ingest amitraz through licking and grooming. Amitraz is vastly broken down to metabolites in the liver. This occurs rather fast in ruminants, pigs and dogs, but much slower in horses, which may explain why they do not tolerate amitraz. Excretion is achieved through the kidneys: 24 hours after treatment >60% of the administered dose is already excreted.
Mechanism of action of amitraz
The acaricidal activity of amitraz is due to its antagonistic effect on octopamine receptors of the nerve cells in the brain. Parasites become hyperexcited, paralyzed and eventually die. This mode of action is different from those of synthetic pyrethroids, organophosphates and other ectoparasiticides.
Click here to view the list of all technical summaries of antiparasitic active ingredients in this site.