Imidacloprid is an antiparasitic active ingredient used in veterinary medicine in dogs, cats and livestock against external parasites (fleas, flies, lice, etc.). It is also used against agricultural and household pests. It belongs to the chemical class of the neonicotinoids.


Type: pesticide
Chemical class: neonicotinoid


Molecular structure of IMIDACLOPRID







Type of action: Broad-spectrum, contact, non-systemic insecticide, lousicide
Main veterinary parasites controlled: fleas, lice

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 imidacloprid used in domestic animals.


Oral LD50, rat, acute*:  450 mg/kg
Dermal LD50, rat, acute*: >5000 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.

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

  • CODEX: Yes
  • EU: Yes
  • USA: Yes
  • AUS: Yes

In April 2013 the EU prohibited for two years the use of several nicotinoids on various crops due to suspected detrimental effects on bee colonies. This should have no influence on veterinary uses of neonicotinoids.

* This information is an indicator of the acceptance of an active ingredient by the most influential regulatory bodies for use on livestock. An MRL for meat may be established also for agricultural pesticides that are not approved for use on animals but are used on commodities fed to animals. It may be also established 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 imidacloprid safety.

General safety information for 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: 1990
Introduced by: BAYER
Some original brands: ADVANTAGE
Patent: Expired (particular formulations may be still patent-protected)

Use in LIVESTOCK: YES, very scarce
Use in
DOGS and CATS: YES, abundant

Main delivery forms

Use in human medicine: No
Use in
public/domestic hygiene: Yes
Use in
agriculture: Yes
Generics available: 
Yes, numerous but not in all countries



In pets: No
In livestock: Yes, in houseflies (Musca domestica) in livestock operations. 

Learn more about parasite resistance and how it develops.


Imidacloprid is a modern "classic" insecticide, introduced in the 1990's. It belongs to the neonicotinoids and was BAYER's own flea active ingredient in the ADVANTAGE product range. It is extensively used in agriculture.

Efficacy of imidacloprid

Imidacloprid has a broad spectrum of activity against insects (e.g. fleas and lice), but no efficacy whatsoever against ticks or mites.

In dogs and cats it is used a lot in spot-ons (= pipettes), alone against fleas and certain lice species, or in mixtures with other active ingredients that broaden the spectrum of efficacy to control ticks or other parasites. As most flea spot-ons it controls existing flea infestations in about 1 to 2 days, and provides about 4 weeks protection against re-infestations.

Use of imidacloprid on livestock is very scarce. It is approved for use as a louisicide on sheep in a few countries (e.g. Australia), and there are also a few pour-ons for cattle, mainly against horn flies (in Latin America).

For off-animal use there are also several baits against houseflies and other nuisance flies, and a few formulations for premise and environmental treatments of livestock operations.

Interestingly, BAYER introduced imidacloprid for pets in the 1990's but not for livestock. Later it was introduced as an off-shears sheep lousicide in Australia and New Zealand. BAYER did not introduced it for use in cattle.

Pharmacokinetics of imidacloprid

Imidacloprid is quite lipophilic. When applied topically to animals it quickly goes into the lipids in the hair-coat and the body surface. This allows a rather long residual effect against fleas.

After topical administration to dogs and cats imidacloprid remains mostly on the animal's surface and is not absorbed. However a certain amount can be ingested through licking and grooming. Ingested imidacloprid is vastly absorbed to blood and quickly metabolized in the liver. Excretion runs mainly through urine (~75%) and feces and is completed in about 48 hours.

Mechanism of action of imidacloprid

As all neonicotinoids imidacloprid is an agonist of the nicotinic acetylcholine receptors. It takes the place of the normal neurotransmitter acetylcholine in the receptors, which cannot be deactivated by acetylcholinesterase and remains irreversibly blocked. This leads to an over stimulation of the nerve cells, to paralysis and to death of the affected insect.

These receptors are found in the central and peripheral nervous system of mammals, but only in the central nervous systems of insects. Neonicotinoids bind much more strongly to insect receptors than to mammal receptors, which makes them relatively safe for domestic animals and humans.

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