For dogs up to 11kg . Each pack contains 6 chewables, to be given as one per month for the prevention of heartworm. Heartgard Plus also controls roundworm and hookworm, but not tapeworm or whip worm. This product should only be administered if your dog has been on a regular heartworm preventative program. Consult your veterinarian if you have not used a heartworm preventative on your dog before, or if there has been a period where treatment has lapsed.