advantus® Flea Control Soft Chews for Small Dogs 4-22 lbs, 7 countadvantus fights fleas fast! One flavored soft chew starts killing fleas on your dog within an hour. advantus is the first FDA approved soft chewable for dogs that is available without a prescription. For the treatment of flea investations on dogs and puppies 10 weeks of age and older and weighing 4 pounds or greater. advantus is in and out of your dog's system in 24 hours.