If there are parasites in the dog's body, it may cause diarrhea and soft stools, and some dogs will pull out the adult worms. Some dogs with weaker stomachs or older dogs will react more strongly to the medicine, causing diarrhea, vomiting, and even retching. If there are no parasites in the dog's body, there will generally be no abnormal reactions.

If a dog ingests an overdose of anthelmintics, it may develop symptoms of poisoning. Generally, after deworming the dog, intestinal repair drugs and probiotics are also needed to regulate the gastrointestinal tract.