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Pyriproxyfen: Flea Egg & Larvae Treatment for Dogs & Cats Guide

Published on November 1, 2024
Updated on November 5, 2025
Reviewed by Petco's Veterinarian Team
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Pyriproxyfen is an insect growth regulator which will inhibit the hatching of flea eggs and the development of flea larvae.

Summary

Used For:

Flea control in dogs and cats

Brands:

Nylar

Species:

Dogs and cats

Other names:

Drug type:

Anti-parasitic

Prescription required:

No

Pregnancy and lactation:

Safe for use in pregnant and lactating animals

Side effects:

Skin irritation

General description

Pyriproxyfen is used to control flea growth in dogs. It will not kill adult fleas or any stages of a tick. It must be applied to the pet's skin to be effective. It is extremely safe.

Uses

Flea control

How it works

Once the female flea comes in contact with a dog treated with pyriproxyfen, eggs laid by that female from that point on will not hatch. Flea larvae that come in contact with the treated pet will not develop. This helps prevent a continual flea problem.

Dosage

Dosage varies depending on which product is used.

The medication is applied topically to the pet's skin.

Follow manufacturer's directions.

Forms

Pyriproxyfen is available as an ingredient in several topical flea control products.

Storage information & handling

Store in a cool, dry place, out of direct sunlight.

What results can I expect?

Pyriproxyfen stops flea larvae from growing as well as flea eggs from hatching.

Missed Dosage

If a dose is missed, consult your veterinarian.

Overdose / acute toxicity

Unlikely. Because insect growth regulators mimic insect hormones, which are unlike hormones in cats and dogs, they are extremely safe. These products can also contain Permethrin which is toxic to cats!

Side effects

*May see irritation or redness on the skin. If sensitivity occurs, bathe in mild shampoo and contact your veterinarian.

Contraindications

*Do not use on cats hypersensitive (allergic) to it.

*Do not get product in pet's eyes or mouth.

Drug interactions

Do not use with other topical pesticides unless directed by your veterinarian.

Precaution

Pyriproxyfen will not kill the adult flea and does not stop the flea from biting and causing flea allergy dermatitis.

Pyriproxyfen will not kill any stage of ticks.

Sources

Saunders Handbook of Veterinary Drugs

Disclaimer
The information contained on this page is for educational purposes only. This medication should only be given under the advice of a veterinarian who has examined your pet under the laws applicable to your state of residence.

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