Major Uses

Fipronil is a phenylpyrazole antiparasitic drug used to kill ticks and adult fleas. The drug works by interfering with the spinal cord and brain in the parasitic insects, causing their death. It is a topical agent that collects in the skin's oils and hair follicles and is not absorbed by the body.

Fipronil's effects take about 24 hours to begin and last about 30 days. This product is used in both dogs and cats. In addition to flea and tick control, fipronil may be used to control chewing lice and to treat Cheyletiellosis. It also helps in the control of sarcoptic mange in dogs.

Common Precautions

Side effects and overdose are very rare.

Fipronil is not for use in pregnant, geriatric, nursing, or debilitated animals. It is also not recommended for use in puppies and kittens less than 8 weeks of age. Temporary skin irritation at the site of application is common and should disappear. Although fipronil remains effective after swimming and bathing, it is necessary to wait 48 hours after application before shampooing.

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


Fipronil should be stored in a cool, dry location and at room temperature. It should be kept away from heat sources and direct sunlight. Exposing this product to heat or moisture may cause it to break down; it should not be stored in the bathroom or above the kitchen sink. This and other medications should be kept away from children and pets.


Fipronil is available in a topical solution and as a topical spray.

Dosing is based on weight. Dogs up to 22 pounds should be treated with one 0.67 ml pipette of topical solution, dogs 23 to 44 pounds should use one 1.34 ml pipette, dogs 45 to 88 pounds need one 2.68 ml pipette, and dogs weighing 89 to 132 pounds should be treated with one 4 ml pipette. Cats should be treated with one 0.5 ml pipette. The topical spray is dosed for cats and dogs at 1.5 to 3 ml per pound of body weight.

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. Each dose lasts about 30 days. If a dose of fipronil is skipped, it should be administered as soon as possible. It is important that two doses of this drug are never administered at the same time.

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.