Capstar, for flea infestations on dogs and cats. FAST ACTING: Begins working within 30 minutes. Capstar may be used as needed, as often as once per day, whenever you see fleas on your pet.Capstar is safe for use in dogs, puppies, cats and kittens 4 weeks of age and older, and 2 pounds of body weight or greater. Capstar is also safe for pregnant or breeding animals. Each package contains six tablets.