Heartgard is a medication commonly used in the United States to prevent heartworm disease in dogs. It comes in the form of a chewable tablet that is administered monthly. The active ingredient in Heartgard targets and eliminates the larvae of heartworms before they can mature and cause damage to the dog’s heart and lungs. It is also effective against certain intestinal parasites, such as roundworms and hookworms. Heartgard is typically prescribed by veterinarians, and proper dosing is important to ensure its effectiveness. Regular use helps protect dogs from the potentially severe and costly effects of heartworm disease.