Capstar is a flea control pill given orally and designed to start working within 30 minutes to completely eliminate all the adult fleas on your dog within four hours. Capstar flea killer works great to kill flea infestation on your pet quickly, however, Capstar flea treatment effects last only 24 hours, so Capstar is not meant to serve as preventative flea control product against new fleas after the 24 hour period. Consequently, Capstar works best as a compliment to other flea control prevention products such as program