A single dose of Capstar should kill the adult fleas on your pet. If your pet gets re-infested with fleas, you can safely give another dose as often as once per day. It is safe for use in dogs, puppies, cats and kittens 4 weeks of age and older. and 2 pounds of body weight or greater. Weigh your pet prior to adminstration to ensure proper dosage. It is also safe for use in pregnant or breeding animals. Begins working within 30 minutes. In studies it achieved greater than 90% effectiveness against adult fleas on dogs within 4 hours and cats within 6 hours.