Your furry friend must have a current heartworm test result on file with your veterinarian in order to be prescribed heartworm medication. Please visit your veterinarian to have this test performed annually to protect your four-legged friend. Revolution is a medication that is applied directly to your furry friend’s skin to protect them from biting critters. When applied every 30 days, Revolution protects against heartworms and fleas. It may also be effective in preventing and treating ear mites, roundworms, and hookworms.