Panacur is a brand name for fenbendazole. They are the same drug. Panacur contains fenbendazole as its sole active ingredient, manufactured by Intervet (operating as Merck Animal Health) and used to treat parasitic worm infections in animals. If your vet prescribed one and you’re seeing the other name on the label, you’re looking at the same medication.
Panacur, Safe-Guard, and Other Brand Names
Fenbendazole is the generic drug name. Panacur is the most widely recognized brand, but it’s not the only one. Safe-Guard is another common brand containing the same active ingredient at the same concentration. Both are available over the counter in many formulations.
The brand differences come down to target species and packaging rather than the drug itself. Panacur C is formulated specifically for dogs, sold as granules you mix into food at a concentration of 222 mg per gram. Panacur is also FDA-approved for horses, cattle, swine, and goats. Safe-Guard covers a similar range of animals and comes in paste and medicated feed pellet forms. The fenbendazole inside each product is identical.
What Fenbendazole Treats
Fenbendazole is a broad-spectrum dewormer, meaning it works against several types of intestinal parasites rather than just one. In dogs, it’s FDA-approved to treat and control roundworms, hookworms, whipworms, and one type of tapeworm. It’s also commonly used off-label to treat Giardia, a microscopic parasite that causes diarrhea. The Companion Animal Parasite Council notes that fenbendazole at the standard dose for 3 to 5 days is effective at eliminating Giardia in dogs, and a 5-day course is typically used for cats.
In horses, fenbendazole targets strongyles (large and small), pinworms, and roundworms. Livestock applications in cattle, swine, and goats cover their own species-specific parasite profiles.
How It Works
Fenbendazole kills parasites by disrupting their internal scaffolding. Every cell has a structural framework made of tiny protein tubes that help it divide, move nutrients, and maintain its shape. Fenbendazole binds to the building blocks of those tubes, causing them to fall apart. Without that structural support, the parasite can’t absorb energy, can’t reproduce, and dies. This mechanism is highly selective for parasites, which is why the drug is well tolerated by the animals taking it.
Dosing and Administration
The standard dose for dogs is 50 mg per kilogram of body weight (about 22.7 mg per pound), given once daily for 3 consecutive days. Panacur C granules are designed to be mixed into a small amount of your dog’s regular food. You may need to moisten dry kibble so the granules stick. The key is making sure your dog finishes the entire medicated portion at each meal.
For Giardia treatment, vets often extend the course to 5 days at the same daily dose. This is considered extra-label use since the FDA-approved label specifies 3 days for intestinal worms.
Safety and Side Effects
At the labeled dose and duration, fenbendazole has an excellent safety record. Most dogs tolerate it without any noticeable side effects. Mild digestive upset is possible, particularly if dying parasites cause temporary irritation as they’re expelled.
The more serious concern involves extended use beyond the approved 3-day course. The FDA issued a letter to veterinarians noting 12 reported cases (as of October 2023) of bone marrow suppression in dogs that received fenbendazole for longer than labeled, ranging from 5 to 14 consecutive days. Bone marrow suppression reduces the production of blood cells, which can cause dangerous drops in white blood cells, red blood cells, and platelets. This is rare, but it’s the reason vets monitor dogs closely when prescribing longer courses for conditions like Giardia.
Not Approved for Humans
Fenbendazole has gained attention online as a self-treatment for cancer in humans, but the FDA has never approved it for human use for any purpose. It remains strictly a veterinary drug. Animal-grade medications are not manufactured to the same purity and safety standards as human pharmaceuticals, and dosing guidelines don’t translate across species. The American Cancer Society has specifically cautioned that taking a drug intended only for animals can be unsafe.
Withdrawal Periods for Livestock
If you’re using fenbendazole in food-producing animals, withdrawal periods apply. Cattle cannot be slaughtered for human consumption within 13 days of the last treatment, and milk collected during treatment and for 60 hours afterward must be discarded. Swine have a shorter 4-day withdrawal period before slaughter. These timelines ensure no drug residues remain in meat or dairy products that reach consumers.