Oral Pill (Program, Capstar, Comfortis) These products prevent flea eggs from hatching when administered orally to pets once a month at mealtime. Cats are fed Program in tablet form, whereas cats are fed a liquid suspension mixed with their food. Different tablet sizes and suspension doses are prescribed according to the weight of the animal. When an adult female flea bites a Program treated dog or cat, the flea ingests the active ingredient (lufenuron) which then passes into her eggs and prevents them from hatching. A companion product, Sentinel™, contains both the flea control ingredient and heartworm medication all in one dosage. Pet owners can break the cycle of flea development and prevent future generations by killing the eggs as they are laid on the pet, or by eliminating the egg-laying adults. The easiest way to do this is to take action before flea problems get out of control. Several products are available which are convenient and effective.