Selamectin is a topical parasiticide and antihelminthic used on dogs and cats to treat and prevent infections of heartworms, fleas, ear mites, sarcoptic mange, and certain types of ticks in dogs as well as prevent heartworms, fleas, ear mites, hookworms, and roundworms in cats. It also removes 2 types of lungworm in cats and one type of lungworm in dogs.