Brand: DYSECT SHEEP 12.5 g/L Pour-on

Company: ZOETIS

FORMULATION: «pour-on» for topical administration.

ACTIVE INGREDIENT(S): alpha-cypermethrin: 1.25% = 12.5 g/L

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


PARASITES CONTROLLED* (spectrum of activity)

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


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

  • Liceticks & blowfly strike:
    • 40 mL for animals weighing 25 kg or more.
    • 25 mL for animals weighing less than 25 kg.
    • For dosages of 40 and 25 mL apply as two half-doses. Apply the first half-dose evenly along the back line from the neck to the saddle and the second half-dose evenly from the saddle to the tail head and around the rump. 
  • Head flies: 5 mL/animal for all animals. Reduces the incidence of headfly strike in sheep and lambs for up to 6 weeks.
  • Lice: A single treatment will normally kill all lice.
  • Ticks: Provides control of ticks in sheep for 8 to 12 weeks.
  • Blowfly strike: Provides protection against blowfly in sheep and lambs for up to 8 to 10 weeks. Re-treatment may be necessary after this period. For the treatment of blowfly strike, a single treatment applied to the infected area will ensure blowfly larvae are killed.
  • Because alpha-cypermethrin is retained in the wool grease of the fleece, it is recommended that the product be applied to sheep with a minimum wool length of 1.0 cm.


  • LD50 (acute oral) in rats: 79-400 mg/kg for the a.i. depending on the carrier.
  • LD50 (acute dermal) in rats: >2000 mg/kg for the a.i..
  • Estimated hazard class according to the WHO: U, unlikely to present acute hazard.

Suspected poisoning? Read the article on cypermethrin safety in this site.

Withholding periods (=withdrawal times) in days for meat & milk (country-specific differences may apply: read the product label)

  • Meat: 49 days
  • Milk for human consumption: not for use in sheep producing milk for human consumption.

WARNING !!!: Never use on humans, dogs or cats. Synthetic pyrethroids are toxic to cats!

2nd-generation synthetic pyrethroids (e.g. 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 is usually weaker in sheep than in cattle.

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


Risk of resistance? YES, moderate. Biting lice developed high resistance to synthetic pyrethroids in Australia and New Zealand in the 1990s. In Australia they were eventually withdrawn from the market for biting lice control on sheep. Several cases have been reported in the UK as well, but so far it seems to remain a limited problem. Nevertheless it is a warning, and the more synthetic pyrethroids are used against biting lice, the higher the risk for resistance to develop.

This also means that if this product does not achieve the expected efficacy against the mentioned parasites, it can 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 development by lice 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: UK & other EU countries
GENERIC BRANDS available? YES, abundant in the EU and Australia.

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

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


DYSECT SHEEP 12.5 g/L Pour-on Solution from ZOETIS is one of the numerous insecticidal pour-ons for cattle, sheep and other livestock containing synthetic pyrethroids for the control of flies, lice, mites, ticks and other external parasites. Worldwide there are hundreds if not thousands of such pour-ons. Besides cypermethrin, numerous other synthetic pyrethroids are used in such pour-ons, e.g. cyhalothrin, deltamethrin, permethrin, etc. They all have a similar spectrum of activity and a comparable safety profile.

Cypermethrin is one of several Type-II synthetic pyrethroids, introduced by ICI & SHELL in the 1970s. Worldwide it is massively used in veterinary products as well as in agricultural and hygiene pesticides. Alpha-cypermethrin is one of several standard isomer mixtures of cypermethrin (see below).

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 of the parasite (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 some parasites may survive because the concentration is not high enough to kill them.

It is useful to know that the active ingredients of many synthetic pyrethroids consist in a mixture of various optical isomers, typically those called "cis", and those called "trans". Cypermethrin has 8 isomers, 4 cis and 4 trans. Manufacturers of active ingredients usually supply the raw material in standard qualities, for cypermethrin typically e.g. in a 40/60 or 80/20 cis/trans ratio. Alpha-cypermethrin is a mixture of only 2 cis isomers, i.e. it is a 100% cis mixture. It happens that the efficacy against parasites and the mammalian toxicity of these isomers are significantly different. Typically cis isomers are more effective insecticides but also more toxic to mammals. Obviously a cis/trans 80/20 mixture is more potent than a cis/trans 40/60 mixture. Qualities with a higher cis content are usually also more expensive. And the higher the percentage of the most active isomer, the lower the rate that is required for achieving the same efficacy. If a manufacturer does not disclose the cis/trans ratio of the active ingredient used in its products it may be confusing because he may be selling the "same" product as another manufacturer, but the use recommendations are different.


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.