
hi sarah,
i remember that capstar can be used weekly and it would be ok to treat a badly infested animal with, but you also need to treat your house as 95% of the flea life cycle is in your house/carpets etc. otherwise new fleas keep hatching out and jumping straight back on the dog! no flea treatment can prevent your dog picking up fleas, but treatments like frontline and stronghold remain in the system and can kill off any fleas that are picked up. frontline stays on the skin, lasts 2 months and will kill any fleas within 24/48 hours. stronghold needs to be applied monthly. so something like this will prevent reinfestation as the fleas are killed so quickly.
in my practice frontline spray works out pretty cheap, we use more of this than capstar. if you are relying just on capstar it only works on the day it is given, so i dont think is a good long term treatment. personally i dont routinely treat my dogs, i check them regularliy and only treat them as needed, i dont like the idea of giving them a chemicals "just in case" however saying that they have never had fleas in the last 3 years!
hope this helps,
kelly