It depends on the size of the dog but generally it would take a large amount of horse wormer to kill a dog. Why can horse wormer kill a dog? Horse wormer is poisonous to dogs because it contains ivermectin which is toxic to dogs in high concentrations.

• Sep 20, 2011Horse dewormer paste is formulated for a horse whose intestines are 100 ft in length it takes 2 days for paste to pass through, dogs have very short in length intestines it travels too fast to work properly they basically poop most of it out before it can kill any worms. if your vet tells you its ok to use a horse wormer i would be getting another vet!

• Dec 05, 2021Moxidectin, the active ingredient in Quest, and ivermectin, the active ingredient in many brand name equine dewormers can be very toxic to dogs and cats. The equine products contain levels of these compounds that are unsafe for small animals. It only takes a very small amount to be toxic to small animals.

• Jul 06, 2022Will horse wormer kill heartworms in dogs? 🐶 Is horse wormer toxic to dogs? Moxidectin, the active ingredient in Quest, and ivermectin, the active ingredient in many brand name equine dewormers can be very toxic to dogs and cats. The equine products contain levels of these compounds that are unsafe for small animals. It only takes a very small amount to be.