Brand: CYLENCE ® Pour-on


FORMULATION: «pour-on» for topical administration.

ACTIVE INGREDIENT(S): cyfluthrin: 1% = 10 g/L

CHEMICAL CLASS of the active ingredient(s): synthetic pyrethroid


PARASITES CONTROLLED* (spectrum of activity)

* Country-specific differences may apply: read the product label.


* Country-specific differences may apply: read the product label.

Apply product down the backline at the rate of:

Weight Horn flies & face flies

Biting and sucking lice

Dosage (mL) Dosage (mL)
<400 lbs. 4 8
400 - 800 lbs. 8 16
>800 lbs 12 24

For horn flies, repeat treatment as needed, however do not apply more than once every two weeks and do not apply more than four times within any 6-month period.


  • LD50 (acute oral) in rats: 2075 (♀) - 2534 (♂) mg/kg (according to MSDS)
  • LD50 (acute dermal) in rats: >2000 mg/kg (according to MSDS)
  • Estimated hazard class according to the WHO: III, slightly hazardous

Withdrawal time in days for meat & milk: USA & Canada: NIL

WARNING !!!: Never use on humans, dogs or cats. Pyrethroids are particularly toxic to cats!

2nd-generation synthetic pyrethroids (e.g. cyfluthrin, cyhalothrin, cypermethrin, deltamethrin, permethrin, etc.) are irritant to the eyes and the skin, both of humans and livestock. The inert ingredients in the formulation may worsen this side effect. Irritation can be particularly problematic for dairy cows because it can significantly hinder handling for milking.

You may be interested in the following articles in this site dealing with the general safety of veterinary products:


Risk of resistance? YES, resistance of horn flies to synthetic pyrethroids (incl. cyfluthrin) is widespread in the USA and worldwide, and can be very high.

This means that if this product does not achieve the expected efficacy against the mentioned parasites, it may be due to resistance and not to incorrect use, which is usually the most frequent cause of product failure.

Alternative chemical classes/active ingredients to prevent resistance of external parasites through product rotation:

These alternative products may not be available in all countries, or may not be available as pour-ons, or may not be effective against all the concerned parasites.

Learn more about resistance and how it develops.


Are the active ingredients of this product ORIGINAL* or GENERICS**?


*Meaning that they are still patent protected and generics are not yet available
**Meaning that they have lost patent protection and may be acquired from manufacturers of generic active ingredients other than the holder of the original patent.

COUNTRIES where this brand/product is marketed: USA, Canada
GENERIC BRANDS available? YES, numerous. This brand is marketed by ELANCO (previously by BAYER). Cyfluthrin is a synthetic pyrethroid originally discovered and developed by BAYER in the 1980s.

Click here to learn more about GENERIC vs. ORIGINAL drugs.

For an overview on the most used antiparasitic pour-on brands click here.


CYLENCE Pour-on Insecticide is one of numerous insecticidal pour-ons for cattle, sheep and other livestock containing synthetic pyrethroids for the control of flies, lice and other external parasites. Worldwide there are hundreds if not thousands of such pour-ons. Besides cyfluthrin, numerous other synthetic pyrethroids are used in such pour-ons, e.g. cyhalothrin, cypermethrin, deltamethrin, permethrin, etc. They all have a similar spectrum of activity and a comparable safety profile.

Cyfluthrin was originally introduced by BAYER in the early 1980s in both crop protection pesticides and veterinary insecticides. It is scarcely used in veterinary products, more in agricultural and higiene pesticides. It is an excellent insecticide, but not very efficacious against ticks and mites.

All synthetic pyrethroids are veteran pesticides developed in the 1970s-1980s and are basically contact insecticides. This means that when the parasite comes in contact with it (e.g., during the blood meal, after landing on a treated host, etc), the active ingredient that impregnates the host's hair coat penetrates through the cuticle (i.e. the "skin" of insects and other arthropods) into its organism and disturbs essential biological processes in the parasite's body, in this case its nervous system.

After administration to livestock or other animals, synthetic pyrethroids do not have a systemic mode of action, i.e. they are not transmitted to the parasite through the blood or the host. Topically administered synthetic pyrethroids are very poorly absorbed through the skin of the hosts, and what is absorbed is quickly broken down and/or excreted. Consequently the concentration reached in the blood is too low to kill blood-sucking parasites. But this is why they are considered rather safe for mammals, both humans and livestock (cats are an exception: pyrethroids are toxic to them!) and why they leave rather low residues in meat and milk.

All pour-ons containing contact insecticides such as synthetic pyrethroids have the same weakness: they are applied on the back of the animal and spread more or less quickly along the hair coat to other parts of the body, but coverage is usually not homogeneous and some parts of the body are not or only poorly reached. How fast and complete the spreading is depends on a lot of factors (e.g. distance to the delivery point, rain, animal behavior such as grooming, licking, rubbing, etc.) but also on the inert ingredients in the formulation, which may or may not favor spreading. In any case, compared with the backline the concentration of the active ingredient will be significantly lower in body parts that are difficult to reach (e.g. udders, perineum, below the tail, inside the ears, etc), where parasites can survive because the concentration is not high enough to kill them. For this reason such pour-ons are mostly not effective enough against some parasites such as ticksfleas and mites. Irregular spreading may also cause chronic exposure of some parasites to sub-lethal doses, which is known to favor development of resistance.

Control of susceptible (i.e. non-resistant) horn flies is usually good (several weeks), because they spend a lot of time on cattle and thus are exposed to the insecticide for a long period of time. However, if horn flies have become resistant, control will be significantly shorter, if at all. Lice are also exposed to insecticides for a long period of time because they never leave the host. Control of face flies is often not as good, due to their different behavior: they do not spend a lot of time on the animals and visit mainly body parts in the face that are humid with body fluids (eyes, nostrils, around the mouth), where the insecticide concentration is diluted by these body fluids.

All synthetic pyrethroids have a certain repellent effect, mainly on mosquitoes but it lasts usually only a few days, if at all.

It is useful to know that the active ingredients of manysynthetic pyrethroids consist in a mixture of various optical isomersCyfluthrin is a mixture of 4 isomers, beta-cyfluthrin is a mixture of 2 of these 4 isomers, the most potent ones.


This article IS NOT A PRODUCT LABEL. It offers complementary information that may be useful to veterinary professionals and users that are not familiar with veterinary antiparasitics. 

Information offered in this article has been extracted from publications issued by manufacturers, government agencies (e.g. EMEA, FDA, USDA, etc.) or in the scientific literature. No guarantee is given on its accuracy, integrity, sufficiency, actuality and opportunity, and any liability is denied. Read the site's DISCLAIMER.

In case of doubt contact the manufacturer or a veterinary professional.