Program (Lufenuron) is a once-a-month oral suspension for control of flea population in cats and kittens of four weeks of age and older. This product does not kill adult fleas but controls flea populations by breaking the life cycle of fleas at the egg stage. When given orally, Program suspension enters and flows through the cat?s bloodstream. When adult fleas bite the host, they transfer the active ingredient to eggs, which prevent them from hatching and developing into mature adults. Each packet contains six tablets containing the active ingredient Lufenuron, an insect developer inhibitor (IDI) that will give six months of protection to your cat. Treatment may begin at any time of the year and should continue until the end of flea season.