Interceptor Heartworm Medication for Dogs and Cats prevents heartworm disease and controls and removes adult hookworms, adult roundworms and whipworms. Interceptor heartworm medication contains milbemycin oxime, a formulation that disrupts nerve transmission within parasites leading to parasite death Once-a-month Interceptor flavor tabs are palatable and willingly consumed by most dogs and cats. Interceptor heartworm treatment in the white package is formulated for dogs 51-100 lbs and cats 12.1-25lbs. Clinical studies indicate Interceptor heartworm treatment is safe when administered at recommended dose. Interceptor Heartworm Medication for Dogs and Cats requires a prescription.