Major Uses

Fipronil, a phenylpyrazole insecticide, and permethrin, a synthetic pyrethrin, are often used in combination to help control fleas, ticks, mites, lice, and mosquitoes. When used together, these drugs effectively manage insect infestations for a full month. The product is for external use on dogs and is highly toxic to cats.

Fipronil and permethrin protect against many diseases transmitted by fleas and ticks, including tularemia, bartonellosis, Rocky Mountain spotted fever, Lyme disease, ehrlichiosis, babesiosis, anaplasmosis, and tapeworms. Proper use also helps prevent anemia and dermatitis caused by flea bite allergies.

Common Precautions

Fipronil and permethrin may cause irritation at the site of application. This side effect is temporary and should disappear within a few days. Extreme irritation may be controlled by bathing the animal with mild shampoo and rinsing thoroughly. This product should not be used on animals with existing skin conditions without first consulting a veterinarian.

Fipronil and permethrin should not be used on cats or on dogs that may be groomed by cats, as this product is extremely harmful to cats. Fipronil and permethrin should only be used on dogs 12 weeks of age or older.

Fipronil and permethrin can cause moderate eye and skin irritation and should be handled with care. The product should be used cautiously or not at all in pregnant, nursing, debilitated, aged, or medicated dogs. A veterinarian should be consulted for advice. Fipronil and permethrin may interact with other medications and supplements, including other flea and tick control products. It is important to disclose all medical history before beginning treatment with any flea and tick control product.

This product should not be used in animals with a known allergy or hypersensitivity to the drug. An overdose of fipronil and permethrin is dangerous and should be considered an emergency. Any known or suspected overdose should be reported to a veterinarian right away.


Fipronil and permethrin should be stored in the original packaging, away from children and pets, and at room temperature. Partially filled containers have special disposal instructions.


The fipronil and permethrin combination product is available in various sizes for small, medium, large, and extra-large dogs. This product is for topical application only and is not to be ingested.

It is important to use the correct dose of fipronil and permethrin when treating animals for fleas and ticks. If there is any confusion as to the correct dose of this product, a veterinarian should be consulted. 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.

Fipronil and permethrin should be applied no more than once monthly. If a dose of this product is missed, it should be applied as soon as possible. Two doses of this medication should not be applied at the same time or in any 30-day period.

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.