CapAction (nitenpyram) tablets are used to quickly kill adult fleas on both cats and dogs. They are an oral flea treatment that starts working within 30 minutes to an hour, killing fleas that are on the animal at the time of treatment. CapAction is often used as a quick-kill treatment when fleas are present, and can be given daily if re-infestation occurs. safe for dogs, puppies, cats, and kittens weighing at least 2 pounds and 4 weeks of age or older..