Merck Animal Health Safe-Guard Canine Dewormer is for the treatment and control of Roundworms, Hookworms, Whipworms and Taenia Tapeworms in dogs. Safe-Guard Canine is the only over-the-counter pet dewormer for dogs that treats all 4 major intestinal parasites in dogs using only one drug compound, fenbendazole, minimizing your dog’s chemical exposure. Safe-Guard (fenbendazole) Canine Dewormer is safe even for puppies 6 weeks and older and pregnant female dogs. It has no known drug interactions, so it should be compatible with other medications your dog might be taking.