i always use derris dust if the fleas get troublesome. rotenone is the active ingredient. it's used as a safe, organic, biodegradable plant-derived insecticide in gardening, and so is cheap and readily available - ask your horticultural supplier. it kills all fleas, on and off the animal so you can sprinkle it lightly on carpets at night and sweep up next day. although it is of low toxicity to mammals, and healthy cats can deal with the short-lived effects of licking it off their fur, it kills fish and bees, so keep packaging away from ponds etc. don't powder too often though - cats don't mind a few fleas - but when they get to nuiscance levels, that's when to hit 'em - not more than once or twice in a season. http://en.wikipedia.org/wiki/Rotenonehttp://www.pan-uk.org/pestnews/Actives/rotenone.htm
regarding the low toxicity, the anti-herballists call on evidence from cruel experiments on animals injected with frequent doses or force fed it, or on other unrealistic manipulations. however they admit it is very rare for symptoms to be observed in animals since it isn't toxic through the skin. also, you seldom see equally rigorous tests for the pharmaceutical ones like the one that drives your poor cat demented. i've been using it for thirty years on goats, cats, dogs and humans, and we're seeing minimal health problems and a lot of vigorous, healthy, contented longevity.