Johnsons 4fleas for dogs tablets are an easy oral treatment for flea infestations on your medium or large breed dog johnsons tablets are fast acting and easily administered with their effects killing fleas in just 15 minutes johnsons 4fleas tablets can only be fully effective as part of a flea treatment programme that will eliminate fleas and their eggs from pets and their surroundings pet bedding and the household should be vacuumed regularly and treated with a suitable insecticide spray