Permethrin for Dogs

Permethrin is a pyrethroid-class insecticide first registered in 1979. It is commonly found in shampoos, powders, sprays and spot-application flea and tick control products for dogs. Products containing permethrin should never be used on cats as it is toxic to them. Caution must be used when dogs that are treated with permethrin share a household with cats, as the cat may ingest the harmful residue by licking the dog's fur, which can lead to seizures and death.

Significance

According to the Environmental Protection Agency (EPA) in 2006, approximately 2 million pounds of permethrin are applied each year. This includes residential, agricultural and public-health uses. More than 70 percent of permethrin use is non-agricultural. Homeowners account for 41 percent of applications in residential areas, with 55 percent applied by professionals and 4 percent used on mosquito-abatement areas.

Function

Permethrin alters nerve function by interacting with sodium nerve channels, modifying the normal biochemistry of the nerve membranes. It targets the nervous system of insects, causing death by muscle spasms and paralysis. Permethrin is highly toxic to insects, aquatic invertebrates, fish and cats. The drug is classified by the EPA as Category III for acute dermal and acute oral toxicity; as well as Category IV for primary dermal irritation potential. There is no data available for inhalation toxicity.

Types

In addition to being the main insecticide in many dog shampoos, dips and flea powders, permethrin is also combined with the flea-killing drug imidacloprid for additional tick control. Examples of this can be seen in Bayer's popular flea- and tick-control products K9 Advantix, which contains a permethrin-imidacloprid combination; and the permethrin/(S)-methoprene combination insecticide Bio Spot for Dogs by Farnam Companies, Inc.

Comparative Studies

In a study published in the International Journal of Applied Research in Veterinary Medicine (JARVM), three different flea and tick products were tested on 24 healthy beagle dogs. The products compared were K9-Advantix, Advantage and Frontline Plus. The best-performing product was Frontline Plus, which contained not permethrin, but a combination of fipronil and (S)-methoprene. Frontline Plus maintained an effectiveness of 100 percent for 21 days. Results showed that the fipronil/(S)-methoprene combination outperformed both the imidacloprid/permethrin (K9 Advantix) and the imidacloprid (Advantage).

Warning

Do not use any products containing permethrin on cats, and separate any other household animals or cats from the treated dog until the product has dried. Cats should not be allowed to lick the fur of a dog treated with permethrin, as a lethal toxic reaction can occur.

References

• Environmental Protection Agency: Permethrin RED; revised May 2009
• Environmental Protection Agency: Permethrin RED; revised May 2009
• JARVN: Comparative Efficacy Study

Resources

• Over-the-Counter Flea Products
• Dog Flea Powder Fatal for Cats