Fenbendazole: A Complete Guide for Dogs and Cats(1)

At Weierli Group, our medication content is crafted and reviewed by veterinary professionals to address your top questions about how pet medications work, their side effects, and which species they’re intended for. Importantly, this information is not a replacement for personalized advice from your veterinarian.

What Is Fenbendazole?

Fenbendazole is the active ingredient in popular veterinary dewormers designed to eliminate intestinal parasites in dogs and cats. It targets:

• Intestinal worms: Roundworms, hookworms, whipworms, and tapeworms

• Protozoal parasites: Including Giardia.

FDA Approval by Species

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Fenbendazole has formal FDA approval for use in veterinary medicine to treat a range of worms in:

• Horses, cattle, swine, and goats

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• Dogs (specifically for roundworms, hookworms, whipworms, and tapeworms).

Notably, fenbendazole is not FDA-approved for cats or ferrets—but veterinarians may legally prescribe it for these species in certain cases. This is called extra-label (or off-label) use, as it falls outside the drug’s official label instructions.

Available Formulations

Fenbendazole is offered in oral forms to suit different needs:

• Over-the-counter (OTC): Single-use packets

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• Prescription-only: Granules, liquids, chews, and capsules (available via your veterinarian).

• Compounded formulations: Custom-made by a veterinarian or licensed pharmacist for pets with unique needs—for example, if your pet cannot swallow capsules, needs a non-commercially available dosage, or is allergic to an ingredient in FDA-approved versions. Compounded medications are not FDA-approved.