Fenbendazole (Panacur) for Cats: Uses & Dosage

This information is for educational purposes only. Never give your pet any medication without your veterinarian's guidance. Dosing, frequency, and safety depend on your pet's specific health profile.

Fenbendazole is an oral deworming medication in the benzimidazole class. You may see it sold under brand names like Panacur or Safe-Guard. In cats, your vet may use it to treat certain intestinal worms and, in some situations, other parasites such as lungworms or Giardia.

In the United States, fenbendazole use in cats is commonly extra-label, which means your vet is using a medication in a way that is medically accepted but not specifically listed on the cat label. That is common in feline medicine. It does not mean the drug is unsafe, but it does mean the exact dose, schedule, and treatment length should come from your vet.

Fenbendazole is usually given by mouth as granules, a liquid suspension, or a compounded form. Many cats tolerate it well, but the right formulation matters. Some pet parents do better with a flavored liquid, while others find a measured oral suspension easier than granules mixed with food.

Your vet may recommend fenbendazole for roundworms such as Toxocara cati and Toxascaris leonina, hookworms such as Ancylostoma and Uncinaria, and in some references certain tapeworms. Merck also lists fenbendazole among treatment options for the feline lungworm Aelurostrongylus abstrusus.

Fenbendazole is also used in some cats with Giardia, especially when diarrhea is present and fecal testing supports that diagnosis. The Companion Animal Parasite Council lists fenbendazole as one treatment option for cats with Giardia, but treatment plans often include more than medication alone. Cleaning litter boxes, reducing reinfection, and sometimes treating housemate cats can matter too.

This medication is not a catch-all dewormer. It does not cover every parasite a cat can get, and it is not the right answer for every case of vomiting, diarrhea, or weight loss. If your cat has ongoing digestive signs, your vet may recommend a fecal exam before choosing treatment.

Fenbendazole dosing in cats depends on which parasite is being treated, your cat's body weight, the product concentration, and whether your vet is using a commercial or compounded form. Merck lists feline intestinal helminth dosing as 100 mg/kg once or 50 mg/kg once daily for 3 days for certain worms. For feline lungworm, Merck lists 50 mg/kg by mouth for 2 to 5 days. For Giardia, the Companion Animal Parasite Council lists 50 mg/kg once daily for 5 days in cats.

Those numbers are useful reference points, but they are not a substitute for a prescription plan. A small measuring error can matter, especially in kittens or underweight cats. Granules, suspensions, and compounded liquids are not always interchangeable on a teaspoon-for-teaspoon basis.

If your cat spits out part of a dose, vomits after dosing, or refuses food with the medication mixed in, contact your vet before repeating it. Your vet may adjust the formulation, show you a different way to give it, or choose another dewormer that better fits your cat and the parasite involved.

Fenbendazole is generally well tolerated in cats, and serious reactions are uncommon. Mild digestive upset is the most likely issue. Some cats may have vomiting, loose stool, reduced appetite, or drooling, especially if they dislike the taste or if the medication irritates the stomach.

Sometimes pet parents notice temporary stomach upset that is hard to separate from the parasite infection itself. A cat being treated for worms or Giardia may already have diarrhea, poor appetite, or nausea before the first dose. That is one reason follow-up with your vet matters.

Call your vet promptly if your cat has repeated vomiting, marked lethargy, facial swelling, trouble breathing, collapse, or worsening diarrhea. See your vet immediately if your cat seems weak, dehydrated, or cannot keep food or water down.

Published veterinary references report no well-established drug interactions with fenbendazole in dogs and cats, and VCA specifically notes that no known drug interactions have been reported. Even so, that does not mean every combination is automatically appropriate for every cat.

Your vet still needs a full medication list. That includes prescription drugs, over-the-counter products, supplements, probiotics, flea and tick preventives, and any recent dewormers. This is especially important if your cat is very young, pregnant, nursing, has liver disease, or is taking several medications at once.

If your cat is already on another parasite treatment, ask your vet whether the products overlap, complement each other, or increase the chance of stomach upset. The safest plan is a coordinated one, not layering medications at home.