Heartgard Plus for Dogs - 50-100 lbs - 12 Doses | MerialIt doesn't matter whether your dog is a pampered pooch or is active and strong, every dog is at risk for getting heartworm disease, a potentially deadly condition. Prevention is easy with HEARTGARDChewables or HEARTGARD Plus.Given once a month for life, HEARTGARD or HEARTGARD Plus is the easiest way to help protect your pet from deadly heartworm disease. HEARTGARD Plus also treats and controls hookworms and roundworms. If you have a dog, you need HEARTGARD. Ask your veterinarian about HEARTGARD today. . Heartgard Plus for Dogs - 50-100 lbs - 12 Doses | Merial. Sold by Vet Approved Rx.