Interceptor Heartworm Medication prevents heartworm disease and controls and removes adult hookworms, adult roundworms and whipworms. Once-a-month Interceptor flavor tabs are palatable and willingly consumed by most dogs. Interceptor heartworm medication contains milbemycin oxime, a formulation that disrupts nerve transmission within parasites leading to parasite death. Interceptor heartworm treatment in the brown package is formulated for dogs 2-10 lbs of body weight. Interceptor for Dogs should not be used for puppies under four weeks of age or two pounds bodyweight Interceptor Heartworm Medication for Dogs requires a prescription.