Frontline spray can be used early on... or is it advantage puppy? I can't remember LMAO.... I'm pretty sure one of them can be used on 4 day old pups.... I would go to the vet or call and ask if Capstar can be used with nursing dogs, because that will get rid of infestations and its a tablet you can give. Then you can wait a few more days for the frontline thing. The frontline has to be a spray for the pups, not the spot on one.