Major Uses

Permethrin is a type of insecticide called a pyrethrin. These drugs are used topically to kill fleas and ticks. Pyrethrins works by affecting an insect's nervous system, which leads to death. Permethrin is a synthetic pyrethrin, and it is more potent and stable than natural pyrethrins.

When applied to the skin of dogs, permethrin repels ticks before they attach, preventing bites and the transmission of Lyme disease. It also effectively kills fleas with a single monthly dose. This drug may be used to control mosquitoes, flies, lice, and other insects and is available for use on cattle, horses, and other animals. Permethrin should not ever be used on cats.

Common Precautions

Side effects associated with proper use of permethrin are generally minimal. In some cases, redness of the skin at the site of application occurs. Dogs that lick the product from the skin may experience vomiting or drooling. Hair loss, discoloration, and rash are also possible.

Permethrin is not for use on weak, ill, or geriatric animals. Because it is highly toxic to cats, this drug should not be used on dogs in homes with cats. Cats should not ever be allowed to groom dogs being treated with this drug. This drug is for use on dogs at least 7 weeks of age. Permethrin should not be used on pregnant or lactating animals.

Permethrin should not be used on animals with a known allergy or hypersensitivity to the drug. Any known or suspected overdose should be reported to a veterinarian right away.


Permethrin should be stored in a cool and dry location, in its original packaging, and out of the reach of children and animals. It is especially important to keep this drug away from cats. Permethrin should not be exposed to extreme temperatures.


Permethrin is available in liquid form in concentrations of 45 and 65 percent and comes in prefilled applicator tubes. This drug may also be combined with other medications in various flea and tick control products.

This product should be applied to the skin in between the shoulder blades. Dose depends on weight. One applicator tube should be used on dogs weighing under 33 pounds, two applicator tubes should be used on dogs weighing 33 to 65 pounds, and four applicator tubes should be used on dogs weighing over 65 pounds.

This drug is applied once monthly. If a dose is missed, it should be applied as soon as possible and the schedule should be adjusted. It is important not to apply to two doses of this medication at the same time.

Doses may vary in different species, when the drug is given by a different route or concurrently with other medications, and with regards to a patient's age, breed, and health status. A veterinarian's dosing instructions and/or those printed on the medication label should be followed closely.

This information is for general reference only and should not be used for the diagnosis or treatment of any condition of your pet. It's intended as a general reference, this information may not include all possible uses, precautions, directions, reactions (including allergic), drug interactions, or withdrawal times. Always consult your local veterinarian and have your pet examined for any advice concerning the diagnosis and treatment of your pet, including which products and doses are most appropriate. Any trademarks are the property of their respective owners. VetDepot is not a pharmacy. All prescription products are dispensed by our Pharmacy Partner. Article last updated 2/2014.