Strongheart is a veterinary medicine that treats and prevents heartworm disease in dogs. It contains ivermectin to prevent heartworms and pyrantel to treat roundworms and hookworms. Heartworm disease is transmitted by infected mosquitoes and can be life-threatening to dogs if left untreated. Strongheart is a chewable, beef-flavored medication that comes in different strengths for dogs of varying sizes. It should be administered monthly according to a dog's exposure to mosquitoes to effectively prevent heartworms.