Fenbendazole works by disrupting the worms’ ability to absorb nutrients, which weakens them over time and eventually causes them to die.
In most cases, the medication starts affecting parasites within a few hours. However, visible results—such as worms or worm fragments in the stool—may take 1 to 3 days. Veterinarians usually prescribe Fenbendazole for 3 to 5 consecutive days to ensure all stages of the worms are effectively treated.
Even if you do not see worms in your dog’s stool, the medication can still be working internally. Always complete the full course of treatment as directed by your veterinarian to ensure proper parasite removal and prevent reinfection.