Advantage II Flea Treatment for Large Dogs. This highly-effective, veterinarian-recommended treatment is specifically formulated to kill all life stages of fleas on contact with no painful biting required. With three-way protection that kills the eggs, larvae and adults, it breaks the flea life-cycle to help prevent re-infestation of both your house and hound. The waterproof formula for dogs 7 weeks or older and weighing 21-55 pounds continues working for up to four weeks, even after bathing or swimming. Veterinarian-recommended treatment kills all life stages of fleas on puppies and dogs 7 weeks or older and weighing 21-55 pounds. Begins working within 12 hours to kill fleas on contact. Kills eggs, larvae and adult fleas to break the life cycle and help prevent re-infestation. Waterproof formula continues working for up to four weeks, even after bathing or swimming. Convenient, monthly topical application contains imidacloprid and pyriproxyfen; available in packs of 4 or 6 treatments.