There is no definitive answer to this question as the safety of mucinex DM for dogs is ultimately dependant on the individual dog and their personal health history. However, many veterinarians recommend that mucinex DM be given with caution to dogs that have a history of swallowed other medications or food items. Additionally, it is important to consult with a veterinarian if your dog is having difficulty breathing, has diarrhea, or is experiencing other signs of poisoning.