Brand: PERMETHRIN 1% Pour-on
FORMULATION: «pour-on» for topical administration.
ACTIVE INGREDIENT(S): Permethrin: 1% = 10 g/L
CHEMICAL CLASS of the active ingredient(s): synthetic pyrethroids
INDICATIONS: CATTLE (beef & dairy), SHEEP & their PREMISES
PARASITES CONTROLLED (spectrum of activity)
Lactating and non-lactating dairy cattle, beef cattle and calves
- Horn flies, face flies, lice
- Aids in the control of black flies, horse flies, houseflies, stable flies, mosquitoes, ticks
- Houseflies, stable flies, face flies, gnats, mosquitoes, black flies, fleas, little house flies (Fannia spp).
- Aids in control of cockroaches, ants, spiders, crickets
Lactating and non-lactating dairy cattle, beef cattle, calves
- Dosage: Apply 1/2 fl oz (15 cc) per 100 lbs body wt of animal up to a maximum of 5 fl oz for any one animal. Pour-On: Pour correct dose along back and down face. Ready to Use Sprayer: Use undiluted in a mist sprayer to apply correct dose. Apply directly to neck, face, back, legs, and ears. Back Rubber Use: Mix 1 pint per gallon #2 diesel or mineral oil. Keep rubbing device charged. Results improved by daily forced use.
- Pour along back. Apply 1/4 fl oz (7.5 cc) per 50 lbs body wt of animal, up to a maximum of 3 fl oz for any one animal. For optimum control, all animals in the flock should be treated after shearing.
- Premises in and around horse, beef, bairy, swine, sheep, and poultry premises. Animal hospital pens and kennels and “outside” meat processing premises.
- For use as a ready-to-use spot spray or premise spray, use undiluted in a mist sprayer. Apply directly to surface to leave a residual insecticidal coating, paying particular attention to areas where insects crawl or alight. One gallon will treat approximately 7,300 square feet.
For cattle, horses, sheep and goats, repeat treatment as needed but not more than once every two weeks.
For optimum lice control, two treatments at 14-day intervals are recommended.
- LD50 (acute oral) in rats: >5000 mg/kg (according to MSDS)
- LD50 (acute dermal) in rats: >2 mL/kg (according to MSDS)
- Estimated hazard class according to the WHO: U, unlikely to present acute hazard
Suspected poisoning? Read the article on permethrin safety in this site.
Withholding periods (=withdrawal times) in days for meat & milk (country-specific differences may apply: read the product label)
- Meat: USA NIL
- Milk for human consumption: USA NIL
WARNING !!!: Never use on humans, dogs or cats. Permethrin is particularly toxic to cats!
Permethrin and all other 2nd-generation synthetic pyrethroids (e.g. cyhalothrin, cypermethrin, deltamethrin, 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:
- Safety for humans
- Safety for domestic animals
- Safety for the environment
- Hazard classifications of pesticides
Risk of resistance? YES, resistance of horn flies, houseflies, fleas, mosquitoes & cockroaches to synthetic pyrethroids (incl. permethrin) is widespread in the USA and worldwide, and can be very high. Cases of resistance of black flies, stable flies and little house flies to synthetic pyrethroids (incl. permethrin) have also been reported, but prevalence is usually low.
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:
- Carbamates (e.g. carbaryl)
- Macrocyclic lactones (e.g. doramectin, eprinomectin, ivermectin, moxidectin, etc.) only as pour-ons. Injectables and drenches are ineffective against most external parasites.
- Organophosphates (e.g. diazinon)
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**?
- GENERICS (both permethrin & PBO)
*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
GENERIC BRANDS available? YES, numerous. This brand with generic permethrin is marketed by DURVET in the USA.
Click here to learn more about GENERIC vs. ORIGINAL drugs.
For an overview on the most used antiparasitic pour-on brands click here.
Permethrin 1% Pour-on is one of numerous insecticidal pour-ons for cattle, sheep and other livestock containing synthetic pyrethroids for the control of flies, lice, ticks and other external parasites. Worldwide there are hundreds if not thousands of such pour-ons. Besides permethrin, numerous other synthetic pyrethroids are used in such pour-ons, e.g. cyhalothrin, cypermethrin, deltamethrin, etc. They all have a similar spectrum of activity and a comparable safety profile.
Permethrin is a veteran synthetic pyrethroid introduced in the 1970s (by several companies). It is also a broad-spectrum non-systemic insecticide and acaricide massively used in pets, livestock, hygiene and agriculture worldwide. There are thousands of products with permethrin world-wide. It is effective against ticks, flies and certain lice species, but has also a certain repellent effect against mosquitoes, ticks and flies.
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 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 ticks, fleas 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, because they spend a lot of time on cattle and thus are exposed to the insecticide for a long period of time. 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. Stable flies, horse flies, black flies and mosquitoes may bite the treated animal anywhere in its body and remain attached and thus exposed to the insecticide only during their blood meals that last a few seconds or minutes, which is often too short to kill them. Ticks attaching to the hosts in those body parts that are poorly covered with insecticide are also likely to survive.
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 many synthetic pyrethroids consist in a mixture of various optical isomers, typically those called "cis", and those called "trans". Permethrin has 4 isomers, 2 cis, and 2 trans. Manufacturers of active ingredients usually supply the raw material in standard mixtures, for permethrin typically in a 25/75 or 40/60 cis/trans ratio. 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 40/60 mixture is more potent than a cis/trans 25/75 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 one, 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.