Does Fenbendazole Treat all Worms in Dogs? Fenbendazole is a broad-spectrum antiparasitic medication commonly used in dogs to control several types of intestinal worms. It belongs to the benzimidazole class of anthelmintics and works by interfering with the energy metabolism of susceptible parasites. Although fenbendazole can be effective against many common worms, it does not treat every type of worm or parasite that can infect dogs....