Capstar (nitenpyram) is an oral medication used in the treatment of flea infestations on dogs and puppies, cats and kittens 4 weeks of age or older and at least 2 pounds of body weight. Capstar is safe to use in pregnant or breeding animals. Capstar begins to kill adult fleas on the pet within 30 minutes and the effect lasts for 24 hours. This product only treats the pet; to properly control fleas, also treat the environments where pets live.