Capstar Flea Treatment kills fleas on your pet that are in the adult stage. Capstar (nitenpyram), kills almost all adult fleas within 4 hours for dogs and 6 hours for cats. We at Vet Meds for Pets recommend you follow up Capstar flea control with a monthly flea control product such as Program, Frontline or Advantage, then keep Capstar on hand for the times when there is a visible flea re-infestation.