Sentinel Plus is a chewable tablet that is administered monthly to dogs to prevent heartworm disease, control flea infestations, and treat intestinal parasites. It contains two active ingredients that work together to protect against heartworms, fleas, hookworms, roundworms, whipworms, and tapeworms. While generally safe for dogs, some may experience side effects like vomiting or diarrhea and owners should consult their veterinarian if they observe any issues.