Safe-Guard (Fenbendazole) Canine Wormer, 4 gm is a broad-spectrum dewormer for dogs weighing over 31 lbs that is also safe for puppies 6 weeks and older. Safe-Guard petmeds only use one active ingredient, fenbendazole, to control hookworms, whipworms, roundworms, and tapeworms that are infecting your dog.