The medication ivermectin is great for killing off many different types of parasites including heartworms in your dog.
But excessive use and overdose of the ivermectin can be toxic to dogs and cause more harm than good.
Heartworm medication and ivermectin should only be given if you think your dog has been infected with heartworms which happens when your dog gets bit by mosquitoes.
It usually takes 10 to 20 times the recommended dose of ivermectin before it actually leads to death in your dog.
But as long as you follow the vets recommendation of doses of ivermectin or heartworm medication the ivermectin should cause no harm to your dog.
It's only toxic in overdose quantities but in moderation and in the recommended doses ivermectin is safe for dogs.