Capstar is a quick action flea treatment for cats. The oral treatment kills fleas rapidly and eliminates them 100% within 3 hours of administration. Capstar for Cats & Small Dogs: It starts working within 30 minutes and kills adult fleas. This unflavored tablet is easy to dose and is suitable for nursing and pregnant cats. It can be given daily at an interval of 24 hours in case of heavy flea infestation or re-infestation. It is safe t to use in kittens from 4 weeks of age and 0.5 kg.