Ivermectin has been approved by the FDA to prevent heartworm disease in some animals in addition to certain parasites. However, while ivermectin can be used for both animals and humans, humans should never substitute the animal version of ivermectin for the human version. Ivermectin should only ever be used for animals when prescribed by a veterinarian, and it should only ever be used for humans when prescribed by a doctor. Again, only take prescription medications intended for humans and obtained from legitimate sources and prescribed by your doctor.