Heartgard Plus Brown Chewables for Dogs 51-100 lbs (23-45 kg) - No Rx requiredHeartgard Plus (ivermectin pyrantel) 51 100 lbs (23 45 kg) Administer once a month to prevent heartworm disease and to treat and control ascarid and hookworm infections in dogs. Pack Content 6 Chewables Each chewable contains 272 mcg ivermectin and 227 mg pyrantel as pamoate salt. You can't stop mosquito bites. But with HEARTGARD Plus, you can kill the heartworm larvae that are transmitted to your dog by those annoying bloodsuckers, helping to prevent