According to wikipedia information:
Ivermectin is a broad-spectrum antiparasitic agent, traditionally against parasitic worms.
In veterinary medicine ivermectin is used against many intestinal worms (but not tapeworms), most mites,ticks and some lice. But It is not effective for eliminating flies, flukes, or fleas. It is effective against larval heartworms, but not against adult heartworms, though it may shorten their lives. The dose of the medicine must be very accurately measured as it is very toxic in over-dosage. See later for more detail particularly regarding use in dogs.