Capstar (nitenpyram) is a fast-acting flea treatment tablet for use in dogs and cats that starts killing fleas in only 30 minutes. A single dose of Capstar kills 90% of adult fleas within 4 hours for dogs and 6 hours for cats, ridding your pet of these pesky parasites. Capstar is for dogs, puppies, cats, and kittens 2 pounds of body weight or greater and 4 weeks of age or older.