Dicyclanil is an antiparasitic active ingredient used in veterinary medicine in sheep against blowfly strike. It is not used against agricultural or household pests. It is a so-called Insect Growth Regulator (IGR) belonging to the chemical class of the cyano-pyrimidines.

Common name: DICYCLANIL

Type: pesticide
Chemical class: pyrimidine, insect development inhibitor = insect growth regulator


Molecular structure of DICYCLANIL







Type of action: contact and oral larvicide
Main veterinary parasites controlled: larvae (maggots) of blowflies and Wohlfahrtia magnifica

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.


Dicyclanil is an insect development inhibitor very specific for the prevention of blowfly strike in sheep. It does not control any other external parasites of sheep. It is used mainly as a spray-on.

So far it is not used in other livestock, horses or pets, nor against agricultural or household pests.

The table below indicates some usual dosing recommendations for dicyclanil issued by manufacturers or documented in the scientific literature. They may not be approved in some countries.

Dosing recommendations for DICYCLANIL
Delivery Parasites Dose (against dicyclanil-susceptible parasites)
Topical (spray-on) Cochliomyia hominivorax 20 ml product/animal post castration. ~30 days protection.
Topical (spray-on) Blowfly strike 35-100 mg/kg, dep on weight. 18-24 weeks protection.
Topical (spray-on) Blowfly strike 3.75-12.5 mg/kg, dep on weight. 11 weeks protection (AUS).
Topical (spray-on) Blowfly strike 7.5-25 mg/kg, dep on weight. 8 weeks protection (UK).
Topical (spray-on) Wohlfahrtia magnifica 35-100 mg/kg, dep on weight. Up to 24 weeks protection.

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Dosing recommendations for antiparasitics depend on national regulations. 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 for specific information on approved indications.

In most finished products, efficacy and safety depend not only on the amount of active ingredient(s) but also on their formulations (i.e. the type and amount of so-called inert ingredients), particularly in injectables and in topical pour-ons and spot-ons. These inert ingredients can significantly affect the pharmacokinetic behavior (e.g. absorption through the skin or from the injection site, distribution within the body, spreading throughout the body surface, etc.). Generic products usually contain the same amount of active ingredient(s) as the original product, but often in quite different formulations. In many cases, the curative (therapeutic) efficacy of the different formulations is quite comparable, but the protective (prophylactic) efficacy that determines the length of protection against re-infestations may be rather different.


Oral LD50, rat, acute*: 520mg/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.

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 dicyclanil safety (poisoning, intoxication, overdose, antidote, symptoms, etc.).

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
Some original brands: CLiCK, CLIKZIN
Patent: Expired (particular formulations may be still patent-protected)

Use in LIVESTOCK: Yes, moderate, only in sheep
Use in HORSES: No
Use in

Main delivery forms: 

Use in human medicine: No
Use in
public/domestic hygiene: No
Use in
agriculture: No
Generics available: 


In livestock: YES

In 2012 a first field strain of Lucilia cuprina blowflies resistant to cyromazine has been reported in Australia more than 40 years after its introduction. It shows a low resistance factor of 3 and cross resistance with dicyclanil.

In 2020 resistance has been reported in two field strains of Lucilia cuprina in Australia reaching in vitro resistant factors of 13 to 25 when compared with suscetible dicyclanil and cyromazine strains, respectively. In-vivo studies showed that protection against re-infestation was reduced by 69% to 78% when compared with the claims of the manufacturer. These strains also showed a 55% and 33% reduction of the length of protection after treatment with commercial products based on cyromazine and ivermectin, respectively.

Learn more about parasite resistance and how it develops.


Dicyclanil is a pyrimidin derivative, chemically very similar to cyromazine. It is a rather specific insect development inhibitor effective against larvae of most dipteran insects (flies, mosquitoes, etc.) and fleas.

It is used in pour-ons or spray-ons for sheep for preventing blowfly strike and other cutaneous myiasis such as Wohlfahrtia magnifica.

Pharmacokinetics of dicyclanil

Topically administered dicyclanil is poorly absorbed through the skin of sheep (2% to 4%). The absorbed dicyclanil is partly metabolized and excreted through both urine (mainly in the fprm of various metabolites) and feces (mainly unchanged dicyclanil). About 95% of the administered dose is excreted in the 7 days following treatment.

Mechanism of action of dicyclanil

The mechanism of action of dicyclanil has not been elucidated. It is certainly not a Chitin Synthesis Inhibitor like other insect development inhibitors such as the benzoylureas. It seems to acts upon the molting process in a similar way as cyromazine, probably interfering with the process of chitin deposition.

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

A personal message

I was very heavily involved in the development and introduction of dicyclanil in the 1990s during my years in NOVARTIS AH.

Click here if you want to know more about the discovery and development of dicyclanil.