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Active Ingredients in Wormers | Revival Animal Health

Deworming your pets on a regular basis is crucial for their overall health.

Cat and Dog Wormer Ingredients

Dewormers often have different active ingredients, so it’s important to know what each active ingredient does. Here are the top five active ingredients in wormers for dogs and cats:

Pyrantel Pamoate

A very safe and effective ingredient to treat roundworms and hookworms in dogs. To eliminate all stages of the worms, dogs need to be dosed a second or even third time, two to four weeks apart.

Hookworms attach to your pet’s intestines with their little teeth. Sentry® WormX Liquid Dewormer contains pyrantel pamoate and works by paralyzing the worms, so they release their grip and pass in the feces. The worms remain alive in the soil for a short period of time.


Effective against against two types of roundworms in dogs and cats. For maximum effectiveness, Piperazine must be administered at least two times (10 to 14 days apart) to the pet. While effective, piperazine is much less palatable (tasty) than Pyrantel Pamoate.


A very broad spectrum anthelmintic (dewormer) used in both small and large animals. In dogs, fenbendazole such as Safeguard Canine Dewormer is effective against roundworms, hookworms, whipworms and even giardia. Treatment is once a day for three consecutive days.

Fenbendazole works by diminishing the parasites’ energy reserves and limiting their ability to eliminate waste.


The drug of choice for treating adult tapeworm infections in both dogs and fish. Does not kill the tapeworm eggs, so there is a potential for reinfection. To prevent this from happening, pets should be retreated on a regular basis.

Praziquantel eliminates the tapeworms’ ability to prevent digestion by your pet. Therefore, the tapeworms disintegrate and become absorbed into your pet’s body.


Most commonly used as a monthly preventative for heartworm in dogs and cats. At higher doses, it is also effective against external parasites such as lice, mange and ear mites. However, this is not a labeled use and may be toxic to certain patients. Caution is advised when using ivermectin with dog breeds that have the MDR1 gene. Studies have shown breeds such as collies, Shelties and breeds that have collie and Sheltie genetics in them, have a higher sensitivity to the effects of ivermectin. For these breeds consider using Bravecto for mange therapy and Sentinel if you don’t feel comfortable giving heartworm medications containing ivermectin.

Medications with ivermectin only work on parasites that your pet has been exposed to in the preceding month, so it is recommended that heartworm prevention be used year round. Ivermectin works by interfering with the central nervous system of the heartworm larva.

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If you need help with choosing the best worm treatment for dogs and cats, call us at 800.786.4751.


    • American Kennel Club. “Ivermectin for Dogs: Is It Safe?” 21 March 2022.

Written by: Marty Greer, DVM

Director of Veterinary Services

Marty Greer, Doctor of Veterinary Medicine, has 40+ years’ experience in veterinary medicine, with special interests in canine reproduction and pediatrics. She received her Doctor of Veterinary Medicine from Iowa State University in 1981. She’s served as Revival’s Director of Veterinary Services since 2019. In 2023, Dr. Greer was named the Westminster Kennel Club Veterinarian of the Year.

If you need help, call us at 800.786.4751.