Your furry friend must have a current heartworm test result on file with your veterinarian in order to be prescribed heartworm medication. Please visit your veterinarian to have this test performed annually to protect your four-legged friend. Sentinel Spectrum is a monthly oral preventive prescription that guards against heartworms, adult roundworms, adult hookworms, whipworms, and prevents the development of flea eggs. It protects your dog against heartworm disease and intestinal worms, all in a palatable, beef-flavored chewable.We directly source prescription medications from manufacturers and wholesale distributors registered with the FDA and licensed by applicable state boards. Guaranteed genuine, and where applicable, backed by the manufacturer.