A single dose kills all the adult fleas that are currently on your pet. Additional doses can be safely administered as often as once a day, if your pet becomes re-infested with fleas. Capstar Flea Tablets are safe for use in dogs, puppies, cats, and kittens four weeks of age and older and weighing 2 lbs or greater. Capstar tablets are administered orally and begin working within thirty minutes. Studies show that Capstar has achieved greater than ninety percent effectiveness against adult fleas on dogs within four hours and cats within six hours. Each packet contains six tablets.