In most cases, your dog or cat won't show any side effects and will be their normal selves. If they had a lot of worms, you might see these being passed in their poop for a day or two after they have Panacur, but if this doesn't happen it isn't a sign that the Panacur hasn't worked. In most cases dogs will continue as if nothing has happened and there will be no signs they've taken Panacur.